Still the King?
42" TSL Review and Tire Tech

By Bill "BillaVista" Ansell

Photography: Bill Ansell & Terry Brummel
Copyright 2006 - BillaVista Offroad Tech
(click any pic to enlarge)




Tires, tires, tires!

Is there any other component on your rig that elicits such an emotional response, such heated debate, such pride, as its tires? Pull up to a trail ride or event and what's the first thing you notice about the other guys' or gals' rigs? Watch closely and what's the first thing they stroll over and look at on yours? It's not the motor or the gearing or the suspension...it's the tires. And for good reason...whether street-driven or trailered, buggy on 42's or Jeep on 31's - your tires say a lot about your rig.

Whether in mud, snow, or rocks, tires can make or break your rigs performance so it's obviously pretty important to choose the right tires. The ironic thing is, unlike many other components, there's precious little hard data available to compare tires. With engines, axles, and suspension we can talk of horsepower, torque load capability, anti-squat, valving, and spring rates. With tires we're much more reliant on experience, word-of-mouth, gut feel, and reputation.

To complicate matters, in the past several years there has been a marked increase in the number and different types of tires available for your hardcore 4x4. There are old players with new offerings, there are narrow-focus competition tires, there are even new companies more traditionally associated with sports cars selling offroad tires. And with pro competition, sponsorships, marketing deals, advertising, and the Internet full of "experts" it can all get pretty confusing pretty fast.

With this article I aim to give you some ideas to help you decide where to spend your tire dollars. It used to be the off-road crowd were divided into two camps - those that had Super Swampers - and those that wanted them. In essence, the "Swamper" was King. So now I'm going to answer the question: "For an all-round, hardcore, off-road tire - is the Swamper still King? "

Before I go any further, I should point out that this article is aimed at the hard core enthusiast. It's for the individual who places a premium on off road performance - above all else. Whether street driven or trailered; Suzuki, Ford of buggy - it's about serious off-road ability and not about quiet ride, mileage, or tread-wear warranties.

Basic Tire Tech

Before I get into the why's and wherefore's of my favorite tires we should first go over a little basic tire tech. Not only because, as usual, we need to be sure we're talking about the same things, but also because knowing precisely what a tire is made of, how it's made, how it works, and what the differences are between types has a surprisingly large effect on how we view our tires - and ultimately what we decide to buy. I know, I know, you're thinking, "What's to know - it's a tire for God's sake - surely even BillaVista couldn't over-complicate it!" And you'd be wrong ;-)

What is a tire and what does it do?

On the face of it, this bit's actually quite simple. A tire is just a rubber air bladder that contains pressurized air to support the vehicle's weight, right? Well, yes...but it also transmits acceleration, braking, and cornering forces to the road or trail, and acts as a spring between the trail and the wheel.

It's able to do all this because of the way it's constructed. You see, a tire isn't just a rubber balloon - it has a carcass made of plies (or layers) that give it shape, strength, and stability (otherwise when filled with air it would just expand in a wobbly and useless round fashion like a balloon tire in a kids picture). It has a steel bead to clamp it to the rim with sufficient friction to transmit acceleration and braking from the rim to the trail and vice versa. It has tread blocks to grip the road and trail, tread voids to shed mud, snow and water, and it can have cap-plies or steel belts under the tread to stabilize the tread and reduce punctures. The plies themselves are made of chords of fibrous material (polyester, fiberglass, nylon, rayon, steel mesh, kevlar, etc.) woven together and coated with rubber. It is the plies in a tire that give the tire shape and strength and prevent it from expanding like a balloon, thus allowing the build up of load supporting pressure.

What are the parts?

The major parts of a tire are as follows:

Body: The body, also known as the carcass or casing, is the core of the tire. Made up of body plies, it is beneath the tread and inside the sidewalls.

Chords: Lengths of fibrous material (polyester, kevlar, nylon, etc.) that lie at the heart of a ply.

Ply: A fibrous, fabric layer made from chords woven together and coated with rubber.

Body Plies: Layers of rubber-coated fabric that form the body of the tire.

Cap Plies: Optional extra layers of fabric used for circumferential reinforcement in high-speed tires.

Bead: High-strength, rubber-coated, steel cable that clamps the tire to the rim.

Tread: A compound of many natural and synthetic rubbers and other components that contacts the road.

Tread Lug: Raised segment of the tread.

Tread Void: A gap or space in the tread to allow the shedding of mud, snow, and water.

Sidewall: The rubber between the tread and the bead, it provides lateral stability for the tire and protects the body plies.

Shoulder: The area where the tread and sidewall meet.

Inner liner: The innermost rubber layer in a tubeless tire that helps to make it air-tight.

Steel Belts: Belts of steel mesh that lie under the tread to provide puncture resistance and keep the tread area flat for maximum road grip.

Edge Cover: Optional special circumferential reinforcements above the steel belts found in high-speed tires. Also called belt edge strips.

Essentially, a tire is made as follows:

- The beads are formed from steel cable
- Body plies are made from rubber-coated fabric cords
- The carcass is made from body plies stretched from bead to bead
- Optional steel belts and/or cap plies are added on top of the casing (depending on design)
- The tread and sidewall rubber are moulded on
- The inner liner is added.


To have a meaningful discussion about tires, in addition to knowing the names of all these parts, there are some important dimensions of a tire that we must know. These are illustrated and described below:

Overall Width:
The distance between the sidewalls of a tire when it is, mounted on the design rim*, inflated, and unloaded; including any protruding side ribs, raised lettering or decorations.
Section Width:
The distance between the sidewalls of a tire when it is, mounted on the design rim*, inflated, and unloaded; exclusive of protruding side ribs, raised lettering or decorations.
Tread Width:
The width of a tire's tread at the point where it comes into contact with the road, i.e. the width of the contact patch.
Section Height:
The distance from rim seat to outer tread surface of a mounted, inflated and unloaded tire.
Rim Diameter:
Diameter of the rim measured at the bead seats.
Rim Width:
Distance between the two opposite inside edges of the bead seats.
Overall Diameter:
The diameter of the inflated tire, mounted on the design rim*, unloaded.
Overall Diameter = Section Height X 2 + Rim Diameter

* Since a tire's section width and diameter changes depending on the width of the rim on which it is mounted (the tire gets wider and taller if mounted on a wide rim, and narrower and shorter if mounted on a narrow rim), each tire is measured on a specific rim width, called the "design rim". For tires with aspect ratios between 50 and 80, the design rim width is usually 70% of the tire's section width. For tires with an aspect ratio less than 50, the design rim's width is normally 85% of the tire's section width.

Aspect Ratio: There is another dimension of a tire that is useful to know - though strictly speaking it's a calculation rather than a true dimension. It's know as the tire's Aspect Ratio.

Aspect Ratio = Section Height divided by Section Width

Aspect Ratio is the relationship of a tire's height to width when mounted and inflated on a rim of correct size. Aspect ratios are expressed as a two digit percentage such as 80, 70, 60 etc. This number, as a percentage, means the height of the tire's sidewall (its Section Height) is x% of its width. Aspect ratios are also often referred to as the tire's 'series'. For example, if section height/section width is 0.60 (60%), the tire is a 60 series tire.

Why do we care about a tire's Aspect Ratio? Because the height to width relationship determines the shape of the tire on the rim, and, more importantly, determines the performance characteristics of the tire. If the sidewall height of a tire is reduced slightly, the sidewall stiffness is increased greatly. Higher Aspect Ratios deliver greater deflection under load and a softer ride. Lower aspect ratios deliver a wider footprint, quicker response, less slip angle, lower flex rate, less deflection and a harsher ride. Also, typically, a high aspect ratio tire will have a long, narrow footprint, while a low aspect ratio will have a short, wide footprint. At least that's all true in the street-car world. Things are a little different for us because the amount by which we air down our tires overdides the Aspect Ratio in determining the tire's footprint and responsiveness.

Construction - Radial, Bias Ply, and Bias Belted

There are 3 basic types of tires, named for the 3 main ways of constructing a tire, differentiated by the way the body plies are oriented. They are:

Bias Ply tires,
Radial tires, and
Bias Belted tires.

Bias Ply

The body plies in a bias ply tire are laid down at an angle (or bias) to the centerline of the tread, and are stacked one upon the other in a multi-layer criss-cross fashion. These criss-crossing layers are generally oriented 32 to 40 degrees from the centerline of the tread. Since the chords that make up the plies are fibers, they are strong in tension but have no strength in compression. This is why the plies are laid down at a bias and on top of one another - to give the tire its strength in both directions - and is also why there are always an even number of body plies in a bias ply tire. The body plies are frequently made of nylon chords but other materials can be used. Nylon is very strong but is also very stiff. These stiff, strong layers must essentially scissor against each other as the tires flexes which builds heat, causing the tire to run hotter than a radial. Over time, heat degrades a tire. That said - this building of heat is really only an issue in sustained road driving at speed. Bias ply tires also do not have cap plies or steel belts under the tread - as a result, when the tire is loaded by the vehicle the chords are stretched and the entire body supports the weight. Since there are no other layers under the tread, the tread tends to be slightly rounded, creating a smaller contact patch (relative to a same-size radial) that reduces road handling. Because of our practice of airing down this reduced contact patch is of no concern off-road. On the other hand, since bias body plies run from bead to bead there is no transition from a circumferential belt to sidewall - the tread and sidewall construction are the same. As a result, tread can be wrapped around and down the sidewalls of a bias ply tire for extra traction and protection - the perfect example of which is the TSL/SX - a tire not offered in radial design.

Intreco Tire's Super Swamper TSL/SX - photo courtesy Interco Tire Corp.
Extensive sidewall tread on the TSL/SX - possible because of its bias ply construction.

The overlapping, criss-cross plies of a bias ply tire results in a carcass and sidewall that are thick, stiff, and strong. This very strong sidewall more easily withstands trail hazards and punctures than a radial design (where all the chords run in the same direction, are generally made of weaker, more flexible polyester, and there are fewer plies). This is not only because the multiple plies result in a great thickness (making it harder to penetrate completely), but also because of the alternating angles of the bias ply. If an injury does occur in the sidewall of a bias ply tire it is much less likely to completely rip or tear (called a "zipper") than radial tire. Imagine it like this: take 2 wooden boards and glue/bond them together with the grains running in the same direction. Now strike the top edge with an axe - they will split readily....the zipper! Now, bond the same two boards together again, but this time lay one on top of the other at an angle (a bias) of 30-40 degrees. They will now resist splitting completely when struck with the axe - just like the overlapping body plies in a bias ply tire (when abused offroad - not hit with an axe, of course!)

A bias ply tire can be aired down lower than an equivalent radial tire. This is because the heavy-duty sidewalls of a bias ply tire also help support the load more than in a radial. Remember that the plies criss-cross across a bias ply tire. One layer is strong in the weak direction of another. As the tire is compressed and flattened by the load, some of the cords are put under tension where the great tensile strength of nylon results in the sidewall supporting the load in conjunction with the air pressure inside the tire - the result being we need less air pressure in the tire to support the load.

Bias ply construction also presents two additional characteristics - neither of which are of any real concern in a hardcore trail rig. Due to their weight and lack of steel belts or cap plies, bias ply tires tend to be less fuel efficient for highway use than radial tires. Also, nylon has a tendency to take a set when statically loaded, especially when cold, resulting in the "square tire" syndrome.


There are two main differences in the construction of radial tires compared to bias ply tires that account for their dramatically different on and off-road performance characteristics: the orientation of the body plies and the addition of steel belts and/or cap plies under the tread.

In a radial tire the body plies are laid down perpendicular to the center line of the tread - they appear to radiate from the center line - hence the name "radial". There are also usually many fewer body plies than in a bias ply design - up to a maximum of 3 compared to the up to 16 used in a bias ply tire. In fact, a radial tire needs only one body ply, and thus is not only less stiff, but runs much cooler, and weighs less. If more than one body ply is used , successive body plies are layered over the existing ones with all the chords being parallel. In addition, the body plie(s) of a radial tire are generally made of polyester which is softer and not as tough or strong as the nylon common in bias ply tires.

Radial tires also use a wide variety of cap plies and/or steel belts under the tread. These belts are placed in successive layers circumferentially around the casing, under the tread. They are independent from the body plies, are made from a variety of materials (including steel, fiberglass, and nylon) that are different from the materials used in the body plies, and so cause a discontinuity where the sidewall and tread meet. Each belt adds an additional layer in the tread area but leaves the sidewall area untouched.

This belted radial design, this discontinuity between sidewall and tread, results in the tread being independent from the sidewall - the steel belts provide a stable foundation for the tread allowing the sidewall to be more flexible. In a radial tire sidewall flexing does not alter tread pattern. As the tire flattens out under loads or impact, the sidewall plies just bend, adding very little resistance.

The following diagrams illustrate the difference between bias ply and radial tires in terms of the effect of sidewall flexing on tread stability and contact patch.

Thick, stiff, bias ply sidewalls, integrated with the tread, mean that as the sidewall flexes (as in a cornering load) the tread is affected and the contact patch negatively impacted.

In contrast, the flexible, independent sidewalls of a radial flex under loads (as in cornering) and allow the belts to keep the tread flat and stable.



The combination of the radial pattern, softer polyester material, and use of belts (independent tread and sidewall) gives a radial tire more sidewall flex which allows the tire to absorb road shock and noise thus producing a much smoother ride. The softer polyester chords also resist flat-spotting much better than the stiff nylon chords in a bias ply - especially in the cold. On-road it also results in the load being distributed equally across the contact area as well as better traction with less heat build up resulting in longer life and improved fuel economy. By restricting tread movement during contact with the road, the belt plies improve tread life. In addition steel belts protect the casing under the tread against high-speed impacts and punctures.

However, the sidewall is generally weaker on radial tires than on bias tires when it comes to puncture and damage resistance. Part of this is due to fewer body plies and less rubber being used, and part is due to the fact that, in a radial tire, even a small injury can lead to massive tear because the body plies have all their chords running parallel to one another.

Also, since the radial sidewall adds very little stiffness (indeed is designed to be much more flexible), as can be seen in the distinctive radial tire "bulge", the load is almost entirely carried by the air and thus radial tires cannot be aired down as low as bias ply tires carrying the same load.

In addition, the discontinuity between tread and sidewall in a radial tire is the reason radial tires don't have substantial sidewall tread. Because the radial design depends on thin, flexible sidewalls it defeats the purpose to add significant rubber tread to the sidewall, and doing so would cause a lot of heat buildup from radial sidewall flexing. In any case, even if some form of tread is added to the sidewall of a radial their will still be a break in the transition from tread to sidewall.

Other components found in a radial tire but not in a bias ply are bead chaffers and cap plies - usually built into performance tires to enhance cornering and stability at high speeds.

Bias Belted

Bias belted tires are a hybrid combination that have criss-cross bias body plies like a bias ply tire, combined with cap plies / steel belts like a radial tire. Frequently the belts and body plies are made from different materials. For example, a polyglass tire may have polyester plies and fiberglass belts. Bias belted tires have a wider tread area than the bias ply - providing better traction and stopping power. They also have more flexible sidewalls than the bias ply, resulting in less internal heat buildup during driving and consequently greater tread life. On the surface they may seem like an ideal compromise - a way to combine the benefits of both radial and bias ply design. However, they of course also combine the weaknesses of both designs. I believe this is the reason they have never really caught on and are all but nonexistent in the market place - very few bias belted tires are manufactured today. This is probably due to the fact that both bias ply and radial tires fit their niche, accomplish their goals, so well that the potential consumer of either is not willing to compromise either with a hybrid tire. Those seeking tough, durable off-road tires with maximum sidewall strength and tread will choose bias ply tires - those seeking on-road performance, tread-life, and handling will choose radial tires.

Which One to Choose?

Virtually all street/car tires sold are radials due to their superior handling, ride quality, and wear. Radial construction allows the tire to better flex and absorb the irregularities of the road surface. The radial design also produces much less friction resulting in cooler running tires and much longer tread life.

But bias ply tires refuse to disappear from the market. The overlapping, criss-cross reinforcement design of bias ply tires makes them very durable. Since the sidewall is as strong as the rest of the body, it can withstand lateral loads, twisting, and bending which would cause a radial to split - especially in an aired-down tire. This strength and durability of the bias ply construction is also a benefit in high torque conditions like when a spinning tire suddenly gets traction. Also because of the one-piece tread/sidewall design, much more aggressive and functional tread can be added to the sidewall of a bias ply tire.

The following diagram and table summarize the strengths and weaknesses of radial and bias ply construction:


Bias Ply
Tough, durable sidewalls. Flat spot when statically loaded. Don't flat spot when statically loaded. Weak, flexible sidewalls.
Functional sidewall tread - sidewall tread blocks help protect the sidewall and add traction to climb out of ruts and up rocks. Stiff when cold. Not as affected by cold. Susceptible to sidewall splitting - chords do not reinforce each other.
Can be aired down lower for larger footprint and better flotation - stiffer sidewalls bulge less Transmit shock. Softer ride. Weak sidewalls can bulge out quite far, exposing them to danger.
Body plies criss-cross and reinforce each other. Integrated sidewall / tread causes a rounded tread - reducing traction and directional stability (on street). Squarer, flatter tread - better directional stability (on street). No aggressive, functional sidewall tread.
Nylon construction stronger and more abrasion resistant than polyester. Sidewall flexing affects tread contact patch. More stable tread, not affected by sidewall flex. Polyester construction not as tough and abrasion resistant as nylon.
Can withstand lateral loads from rocks and roots without splitting. Scissoring of bias plies as sidewalls flex builds heat quickly. Better, more stable handling and cornering. Must be maintained at higher air pressures to carry equivalent load.
Can survive abuse that would destroy a radial. Require strict attention to air pressure if run on-road. Steel belts give good protection to tread area. Because of separate tread/sidewall design, susceptible to tread separation (the tread rings or "alligators" trucks are always shedding on the highway).
Because of their acknowledged on-road limitations can be uncompromisingly designed with extremely aggressive treads for excellent off-road traction. If run on-road at high speeds, susceptible to ply separation because of heat build up. Run cooler, longer life.  
    Better tread wear, improved fuel efficiency.  


Bias ply tires are the clear choice for serious off-roading because of their sidewall strength, aggressive tread, and ability to be run at low single-digit pressures. For serious, hardcore trail riding, the strength and durability of the bias ply trumps all - after all, when you're wheeling brutal terrain miles from nowhere the best tire is the one that still holds air!

Radials are the best choice for on-road driving because of their softer ride, improved handling, and longer tread life.

If you drive both on- and off-road you have to decide which is more important - the road manners of the radial or the toughness of the bias ply. Me - I'll compromise road manners for trail performance every time. If you're compromising, whichever you choose, there are a couple of precautions to note:

- When running a bias ply tire on the street, strict attention must be paid to tire pressures. The stiff sidewalls can easily disguise an under-inflated tire. Street driving even slightly under-inflated bias ply tires can be hazardous because the scissoring body plies already build a lot of heat - this is exacerbated by under-inflation to the point that the tires can quickly build enough heat to cause ply separation and catastrophic tire failure.

- Radials tires, of course, also need correct air pressure on the street. Excessive heat in a radial tire leads to sidewall cracking, zipper blowouts, and the tread separating from the casing (those rings of tread, or "alligators" you see on the side of the highway are most often the result of radial truck tires, especially retreads, suffering this heat-induced tread separation). Off-road, radials will require more air pressure than bias ply tires to avoid excessive sidewall bulge resulting in sidewall splitting or the sidewall getting pinched between the rim and a rock.

Purchase Considerations

So now that we know the basics, we know enough to make our tire purchase decision ...well, almost!

The last thing to cover is a few ideas on the specs we need to consider in selecting a tire.

Once again I must emphasize the subjective nature of this . This is largely due to two things - the first is the fact that our hardcore offroading needs in a tire are completely and dramatically unlike any other tire users' - from race cars to motorbikes to tractors - there's no one else's use that even comes close to matching our needs. This is closely related to point two - which is: Ours is still a relatively "new" and "emerging" sport - a sport still in its infancy. As a result - there still aren't multi-million dollar competitive series and huge corporate sponsors - the kind that can fund the engineering and R&D required to really get to the bottom of things with hard empirical data. Let me give you an example. The racing world probably knows the most about tires - at least the tires they use. This is the result of many years of well funded and highly competitive, highly focused, research and development. As such - racers, the good ones at least, know about how a few degrees ambient temperature difference, a different track, or a 1/4 lb worth of pressure will affect their tires and therefore their car's handling. They use durometers and pyrometers and heat sensors and chemicals and dry nitrogen and 1/4 pound increments in pressure to tune their tires and extract every ounce of performance from them. Heck, even tractor drivers can research agricultural papers that discuss, in scientific detail, concepts such as ballasting and grip coefficients with certain implements - factors that affect their tire's performance.

We, on the other hand, have no such thing - whether it's lack of funding, knowledge, expertise, or motivation - we don't discuss durometer readings and other scientific, empirical measures - we tell campfire stories! Even rock crawling teams, along with the rest of us, still rely quite heavily on statements that are ambiguous at best - statements such as "I saw those tires in action at <location x> and man, did they ever hook up" or "So and so's tires were the best - they hooked up all day".

All of which is to say that what follows is more subjective than my usual writings. I'm ok with this. I'm confident in my observations based on many years of experience.

So here are the factors to consider when choosing a tire:

  • Size / proportion
    • Probably the first and most important consideration is what size tire to run. It has to be big enough so that a week later you aren't wishing you'd upsized. But you also need to have the motor, clearance, and axles to run the size you want. Another consideration is the "proportion" of the tire - both to your rig and it's own height to width. This is one of the main reasons I chose 42" TSL's. Not only do I think they're perfectly proportioned (44s are too "fat" and 40s just not big enough) but they fit my rig perfectly - I can turn them with ease with a V8 SBC, and my built 1-ton axles handle them well without being overkill. They're simply a great size for hardcore buggies and trucks alike.
  • Tread
    • This will largely be determined by where you wheel. Most of us not only have to wheel a wide variety of terrain, but enjoy doing so. This means most of us need an aggressive tread that does well in rocks, mud, water, snow, etc. The tried and true Three Stage Lug design of the TSL's fits this bill extremely well.
  • Toughness
    • Unless you're lucky enough to be either sponsored or extremely wealthy this is a HUGE concern. Like I said before - at the end of some of the brutal trails I run, the best tire is the one still holding air! Fashionable new radials made by import-car tire companies mounted on huge bling rims may look cool in the parking lot (or not!) - but at the end of the day I'll take a heavy, brutal, tried and true bias ply beast any day.
  • Stickiness
    • Especially for those of us that love the rocks - how soft or "sticky' a tire's tread compound is is an important consideration. However, in the real world of hardcore trail riding it's probably not as important as the tire's toughness - not to me at least. It may be fashionable to talk about wanting "competition compound' sticky tires - but unless you like buying new tires every season they're not the best bet for trail riding. I look at it the same way I did when I rode bikes - sure, talking about having the softest race-compound tires is cool, as is showing them off at the coffee shop parking lot - but it sucks replacing them all the time or having the get torn up or wear out half-way through a tour (or trail)
  • Appearance
    • Don't kid yourself - this is really important - especially when you're dumping cubic yards of dollars in large tires. I know you want to think you're all about form over function - but there's no shame in wanting your rig to look good too. This is, of course, a very personal thing - everyone has their own tastes - just remember - you have to love your rig - every time you look at it - not wince and launch into an explanation of how the tires really work well...honestly...they do...


So we know all about tires and what they're made of. And we know the things we need to consider when purchasing tires. Here's why I chose 15/42-16.5LT Super Swamper TSL's

The Tires

Wow - five 15/42-16.5LT TSL's actually fit in a mini-van!

Here they are mounted, compared to my old 325/85R16 Michelin XML's

The difference in performance is night and day. The old XML's were a good tough tire but my TSL's are FAR superior - they throw mud better, they are softer and stickier, and they grab and hold rocks MUCH better.

Here are some measurements I took - mounted dimensions are on a 16.5 X 8.25 15° bead-seat modified Hummer rim.

  Unmounted Mounted @ 20 PSI Mounted @ 30 PSI
OD (Height) 40" 41" 41"
Tread Width 12.25" 12.75" 13"
Section Width 13" 14.5" 14.5"
Weight 104.5 lbs 164.5 lbs 164.5000001 lbs


Here you can see that the tires are made of four nylon plies - that's four actual body plies (not the 'ply rating' which is a form of load rating - see the "load rating" section later in this article).

They're also Load Range "C" with a max load of 2680 lbs at 30 PSI.

That's equivalent to a 6-ply rating.

The sidewalls are a whopping 3/4" thick!

Specified rim size is from 9.75" to 12" wide, and 16.5" in diameter.

The boy sure looks pleased with "his" buggy's new tires!

Air Pressures

Being big, tough bias ply tires, these TSL's work really well off-road across a huge range of pressures. This gives me a lot of flexibility for tuning them to different terrain and trails. The following pics show the tires at different pressures. Keep in mind that the figures are not some absolute numbers - there's nothing magical about 4 PSI - what works best depends entirely on the weight of your rig.

0 PSI.

Ok, you can't really drive at 0 PSI (yes, I tried - it was hilarious - the whole rig just lurched drunkenly about - that what I'M supposed to do around the campfire!)

But the bottom pic here is an excellent example of why we air-down in the first place - look at the size of that contact patch - it's like a mini tank track!


2 PSI. This is probably the lower limit of what is drivable - and even then you can see there's quit a lot of sidewall wrinkling going on. I rarely go this low but with double-beadlocks and tires this tough at least I know I can if I need the maximum possible contact patch.




5 PSI. I run the majority of hardcore rock and rough trails within a pound or two of 5 PSI. The contact patch is large and flat, the ride nice and soft, but without too much sidewall bulge or wrinkling.




10 PSI. I find ten pounds still gives me a nice soft ride and works well for higher speed trails, mud, and between-trail romping.




20 PSI. At 20 pounds there is virtually no sidewall bulge and the tires are very stable, even at reasonable speed. I use 20 pounds for high-speed ripping around and I also leave 20 PSI in the tires when the buggy is in the garage.


The Look

You can't deny these tires look great on this rig too.

Remember what I was saying about proportions?

Not only are they a great proportional tire in terms of their height and width...

...but they're just right on my rig too. Nothing else would be this right.

They even look good when they're in the air!

The Performance


There's no denying the TSL is a great tire in the mud - one of the greatest ever. The huge lugs and massive voids self-clean as well as any tire out there. I keep telling myself (and others) that I'm a rock-crawler, that I hate mud...but the truth is - it's actually a heck of a lot of fun - especially with the kids onboard yelling "WEEEEEEEEEEEE!!". And having kick-ass tires to fling the goo really rocks!

Here's a series of pics showing me powering out of a deep mud-hole. Sometimes it's hard to catch the mud-flinging action on camera but the last 2 pics show how well the tires can chuck the sloppy stuff!

It's a great feeling to have confidence in your tires when blasting through deep mud and water...especially when you don't know just how deep it is and the kids are egging you on!

Mixed Trails

An awful lot of trail riding is done on mixed trails - some rocks, some mud, some roots and stumps, some dirt, some water... a bit of everything. It's here that the TSL REALLY shines. It's a truly great "all-terrain" tire - I know of no other that does as well in such a wide variety of terrain. There may be tires that do a single job better than the TSL (the Bogger in mud, for example) but no tire does such an great job in ANY terrain. Particularly on slippery, muddy, rocky trails - the TSL kicks ass!

In The Rocks!!

No matter how great a tire is everywhere else - it's performance in the rocks is a make-or-break deal to me - and to most of you reading this too. If a tire sucks when rock crawling it just can't be a great tire. The 42" TSL's do not disappoint. Most of these pics were taken on the most extreme trails available at Paragon Adventure Park in Hazleton, PA by my good friend and excellent photographer Terry Brummel (thanks Terry!) I've wheeled on or with just about every tire out there- and it's my considered opinion that the Super Swamper TSL ranks with the best when it comes to gnarly rock crawling. The toughness, the sidewall strength, the ability to run low single digits, the massive outer lugs, and the tire's soft compound make it a champ in the rocks - here's a look at why:


This is the kind of terrain we're talking about - rocks and boulders galore.



A lot has been made lately of the trend towards bigger and bigger rims - even to the point of ludicrousness. Have you seen a rock buggy on 22" rims? The tires look like low-profile jobbies that belong on a lowered import car. I understand the point that TOO much sidewall can lead to a lack of lateral stability - the sidewall can fold over and even get pinched between rim and rock. Maybe a 44" tire on a 15" rim isn't a great choice for a hardcore rock crawler for this reason - but things have gotten carried way to far in my opinion. And the result is "fashion" is hurting performance.

I believe you still need a good amount of sidewall to flex and conform to the terrain - as long as the tires are tough enough. Look at this series of pics. When climbing a vertical or undercut ledge like this - especially if you want to crawl it or climb with some finesse - you need a tire with enough sidewall, enough toughness, and a grippy enough tread to flex, conform, grab and haul your rig up and over - just like these pics show. Sure - you could just hit it at 40mph with your 40"tires on 22" rims - if that's your thing I guess. Maybe you'd make it, maybe you'd break, maybe you'd just bounce off and look foolish. Me? - I'll stick to what works!



It takes a tough tire to take this kind of deforming and constantly come back for more.


Here's a great series shot by Terry that show the tire's ability to grab the rocks, conform to the rocks, stick to the rocks. Look at the lugs grabbing on - like so many magic rubber fingers - like on my wife's...uh, never mind...just look at the tires!


Note the marks on the sidewall. This is not a poseur tire! This is a tire that gets ridden hard and put away wet - and it works!


All day I was able to grab and climb rocks and stick lines any which way I wanted (well, limited by my driving skill!)

Don't let anybody ever tell you TSL's aren't great in the rocks!



This next series is just one illustration of how tough the TSL is. Believe it or not, this wasn't a setup. We were on a tight, wooded trail with lots of trees - I hate trees - and we were digging and turning and weaving in and out all day. In this particular spot, though you can't see it in the pics, there were large trees on the left and right - forcing me to drive over this stump. And not just any stump - but one chewed by a good ol' Canadian beaver - I swear I'm not making this up - that's what the li'l buggers do, and man does it leave the stumps sharp. Once again, it's great to have tough tires you can trust to hold up to this kind of abuse - there's not many tires you can run over a sharply pointed stump at 4-5PSi in a 5000 lb rig - but the TSL's laughed and asked for more.


If there's a hot buzzword in offroad tires these days - "stickiness" is it. It seems everyone wants the stickiest tires available - just like the pros have. Well, maybe nearly everyone. Coz I don't. I live in the real world - the one without corporate sponsorship, the one without new tires every event or even every season. In fact - most of us live in a world where a new set of 42" tires is only in the budget maybe once every few years.

When you live in this "real" world - you want performance - but your tires have to last too! I've been running my TSLs for 8 or 9 months now - and not only are they plenty soft and sticky the way they are, not only do they perform great in all kinds of terrain, but if they were any softer I'd be in danger of losing my mind! As these next pics show - after only a single recreational "season" they already show plenty of wear - I've been beating them pretty hard after all. I can't imagine them being softer and therefore even more worn! For my money, I think they're a pretty good balance between performance and durability.


More Tire Tech

Tire Sizing Systems

There are many tire sizing systems still in use today, some dating back to the 1930’s and others having come into use only since the 70’s and 80’s. I will explain each one, as you are likely to see any and all of these systems when shopping for off-road tires (Interco themselves use four different systems: Alpha-Numeric, Metric, Flotation, and LT-Numeric).


Earliest system, dates back to the 30’s when there were few tire sizes available (or needed)



9.15 is the section width in inches
15 is the rim diameter in inches

- Using this system you can’t tell the OD of the tire without knowing the Aspect Ratio
- In the 1950s and early 1960s, the standard aspect ratio was 82-84%
- Around 1970, bias ply tires moved to a 78% aspect ratio
- In the 70’s the "standard" aspect ratio dropped to 75%
- Today, Aspect Ratios of 65%, 60% and even as low as 35% are available.
- If you know the AR of the tire in question you can calculate the OD as: (Section Width x Aspect Ratio) x 2 + Rim Diameter (eg. in the above example, if we knew the Aspect Ratio were 78%: (9.15 x 0.78) x 2 + 15 = 29.3" )
- If you don’t know the AR, the only way to tell the OD is to consult the manufacturer’s specifications.

Alpha Numeric

This system began to appear in the late 1960’s. It adds the Load Rating and Aspect Ratio information, but mysteriously drops the Section Width.



H – load rating
78 – Aspect ratio in %
15 – diameter in inches

– This is an almost useless system as we don’t know, nor can we determine, the section width or OD of the tire.
– When radial tires began to appear, an R was added to the designation but this still doesn't’t help us determine size:



– There are some charts available that list common Alpha-Numeric sizes and the equivalent OD and Section Width of the tire, in inches, but these must be used with caution as they are by no means universal. Here is one such chart:

L78/15 = 30x 9.5
N78/15 = 31x 9.5
P78/15 = 33x10.0
Q78/15 = 36x11.5
Q78/16 = 36x10.5
R78/15 = 37x12.5
R85/16 = 37x12.0

-Though the alpha-numeric system doesn’t tell us the OD, we can, however, tell the relative size of tires using this system. Here’s why:

There are only two ways to increases the load carrying capacity of a tire

1) Increase the max pressure it can hold (by altering its construction/composition) or
2) Increase the size of the tire so there are more Square Inches for each Pound of air pressure to push against (a tires load in Pounds is roughly it’s max pressure (PSI) multiplied by the number of Square Inches of its contact patch)

E.g. Load = 50 P/SI x 30 SI = 1500 lbs

The alphabetic load rating system was originally based on this principle, with higher letters being assigned to larger tires able to carry more load. For this reason, we can also say that, for tires using the alpha-numeric system, the higher the letter, the larger the tire. For example, we can see from the preceding chart that an N78/15 (31x9.5) is smaller than a Q78/15 (36x11.5)
- Again, the best way to determine the dimensions of an Alpha-Numeric tire is to consult the manufacturer’s specifications.

Metric (Euro-Metric, P-Metric)

The Metric system first appeared in the 1970’s and was called the Euro-Metric system because it began in Europe. It is the first system that tells us virtually all we need to know, though some information must be calculated from the figures given.



235 is the section width in mm
75 is the Aspect Ratio in %
R denotes radial construction (D = (diagonal) bias ply construction; B = belted bias construction)
15 is the rim diameter in inches

To calculate the complete dimensions:

First change section width to inches by dividing the mm by 25.4

235/25.4 = 9.25” wide

Then calculate the OD in inches by multiplying the Section Width by the Aspect Ratio (to get the height of the sidewall), doubling it, and adding the diameter of the rim

OD = ((9.25*.75)*2)+15 = 28.87 ~ 29”

Therefore a 235/75/R15 is a 29” x 9.25” R15


- This system has becom widely known as the “P-Metric” system as a P appears at the beginning of modern designations to indicate a “Passenger car” tire. Although the system is also used for light truck and special trailer tires.


LT 275/70R16
ST 205/75R14

- System allows rapid comparison of the AR or “profile” of the tire
- Unlikely to ever see anything but an R in P and LT tires, but may see a D or B for certain special tires like ST tires
- The D.O.T. decided to add the "P" to P-Metric to denote that it was designed for passenger car use for load carrying capacity limits.
- Note that P and LT tires are often rated slightly different. If P-rated tire is used in an LT application, you need to de-rate the sidewall load capacity by 9% - 10% according to many tire makers.
- The best system so far, but not perfect (for us) as it requires calculations to give the complete dimensions which we need (because we run such a VAST range of different sizes)
- Early metric sizes may be shown without the AR number



This is because the metric system was implemented in Europe when tires were still chiefly bias ply, available only in a limited number of sizes (due to construction technology of the time) and all using a standard aspect ratio of "82". Therefore, originally it was not necessary to include the AR in the sizing system. With the advent of radial tire construction, tire manufacturer’s were suddenly able to construct better performing street tires by increasing the section width and reducing the sidewall height of the tire. In doing so, they began making tires with aspect rations lower than the “standard” 82% and so it became necessary to include the AR in the metric tire sizing system


The Flotation Sizing system is used for larger, wider tires (LT tires) used on trucks and SUV’s – so named because these tires are supposed to “float” over soft surfaces. It is a convenient system for us as it gives the whole picture at a glance.



36 = OD in inches
12.50 = Section width (NOT tread width)
R = denotes radial construction (absence of the R denotes bias ply construction)
15 = rim diameter in inches
LT = Light Truck tire (may or may not be present)

Tread width may be published by manufacturer, but for us will vary enormously anyway with load and low air pressures.

LT Numeric

For LT tires there also exists another useful system – the LT numeric system – based on the old Numeric system but with the useful addition of the OD.



9 is the approximate section width (in inches)
34 is the approximate overall tire diameter (in inches)
16 is the rim diameter in inches)
LT designates a Light Truck application


- This system is used only for bias ply tires.


Numeric – old and practically useless (unless you’re just shopping for an exact replacement tire from the same manufacturer for your tractor, small trailer, or wheelbarrow). Tires in these sizes will be bias ply.

Alpha-Numeric – only slightly less useless than the numeric system. Might be of some use to those competing in certain sanctioning bodies with rules based on what is written on the tire. E.g. getting away with an aired-down Q-78/15 in a 35” and under class. May be used for radial and bias ply tires.

Metric – has all we need to know, but calculations must be made. Not common in the sizes hardcore wheelers need (38” OD and up). Used with radial and bias ply tires, indicated by an R,D, or B in the designation. Older metric sizing on bias ply tires used a standard, unstated AR of 82%.

Flotation – Most useful “at a glance” info for us, used with both radial and bias ply tires where a radial will always have an R in the designation but a bias may just have no letter. May or may not include the designation “LT” at the end.

LT-Numeric – Similarly useful as the Flotation system, if a little more complicated to read. Used only for LT tires, and only for bias ply construction.

Both the Flotation and LT-Numeric sizing systems tell us the basics of what we need to know. My preference is for the Flotation system as it tells me the info in an easy to read format in the order that I most care about – OD, then width, then rim diameter. Then again, it might just be because that’s the system I grew up reading (and often dreaming) about!

However, it’s not perfect either – in fact, the metric system does offer one advantage – and that’s “at-a-glance” comparison of the “profile” of different tires. E.g.. If we look at:

235/75/R15 and 235/65/R15

We can immediately see that the latter is a lower profile tire.

Traditionally, we wheelers haven’t cared much about a tire’s profile. We just wanted tall tires, either wide or narrow depending on preference. However, in recent years, with the widespread use of single and double beadlocks allowing low single-digit air pressures (to increase contact patch and therefore available traction) combined with the ever increasing need for performance, stability, and predictability demanded by today’s competitive and recreational rock crawling we have begun to take note of the effect of a tire’s profile on it’s performance.

Interestingly, unlike car guys who use an aspect ratio comparing the tire’s sidewall height to its width – we are more concerned with a tire’s sidewall height compared to its overall diameter. Because very large diameter tires (e.g.. 44”), especially on smaller diameter rims (eg. 15”) give a tire a very tall sidewall, often at very low pressure the sidewall will flex excessively so as well as getting a larger contact patch (which is what we want) we get less lateral stability (hindering the ability to stick a technical line in the rocks), unpredictable handling, and increased damage to sidewall injuries (by driving on the sidewall and/or “sidewall pinch” injuries (where the pressure is so low the sidewall essentially collapses and is pinched between the rim and the rocks)). To avoid these troubles we need to run a little more air pressure – we need to find the sweet spot for our rigs weight and our terrain. Of course, this sweet spot is going to be different for different tire sizes on different rims and different tire constructions (radial vs bias ply) – and comparing these (to arrive at the best tire/wheel/pressure combination for us) is where all current sizing methods fall a little short.

If it were up to me we would introduce a new extreme offroad sizing method that would incorporate all the info in the flotation system, along with the aspect ratio (sidewall to width) as well as a dimension I’ll call "profile ratio". This profile ratio would be similar to the aspect ratio except that instead of comparing the sidewall height to the width, it would compare it to the OD (and therefore take into effect the rim diameters effect on the tires performance). It would be calculated as ((OD - Rim Diameter)/2)/OD.

Where AR is read as “The tire is x% as tall as it is wide” the PR would be read as “the sidewall is x% of the tires OD”.

The system would look like this:



42 = Tires overall diameter mounted on approved rim width, inflated to max psi, unloaded.
15 = Tires section width mounted on approved rim width, inflated to max psi, unloaded.
85 = aspect ratio (sidewall height/width x 100%)
30 = profile ration (sidewall height/OD x 100%)
D = Bias Ply (R=radial, B=Bias belted)
16.5 = rim diameter in inches
LT = Light Truck designation.

Imagine how useful this could be. For example, lets say you want a 42” tire (in my opinion we’re always likely to decide on OD first and foremost – basing that decision on either the largest we can fit or the axles will handle; or on what the comp class rules are). To help you compare the different offerings, lets list all the 42” tires Interco offers in the “Big 4” (the 4 most serious off-road options – i.e. TSL, SX, Bogger, And Irok) using my system and see what it tells us.

Style Current Size BV Size AR PR
Bias Irok 14/42-15LT 42x14(96/32 )D15LT 96 32
  14/42-16LT 42x14(93/31 )D16LT 93 31
  14/42-16.5LT 42x14(91/30)D16.5LT 91 30
  14/42-17LT 42x14(89/30)D17LT 89 30
Bias TSL 15/42-15LT 42x15(90/32)D15LT 90 32
  15/42-16LT 42x15(87/31)D16LT 87 31
  15/42-16.5LT 42x15(85/30)D16.5LT 85 30
Generic 35x12.5R15LT 35x12.5(80/29)R15LT 80 29

You can see that there are options with Aspect Rations ranging from 80 to 96 and Profile Ratios ranging from 29-32. Now, all we need to do is develop some sort of system for quantifying the relative performance of tires with different AR's and PR's! Not so easy to do! Probably the best we can do is rely on experience and anecdotal evidence, and combine that with a knowledge of different common tire's specs. But it would at least be a place to start.

Load-carrying Capacity

A tire's maximum load is the most weight the tire is designed to carry. Since a tire's load carrying capacity is related to the tire's size and how much inflation pressure is actually used, maximum loads are rated with the tire inflated to an industry assigned inflation pressure.

Additionally, load ranges are used to separate tires that share the same physical size, but differ in strength due to their internal construction. "Higher" load ranges are used to identify tires that have a stronger internal construction, and therefore can hold more air pressure and carry more weight.

Each load range has an assigned air pressure identified in pounds per square inch (psi) at which the tire's maximum load is rated. Listed below are the air pressures at which maximum load is rated for popular P-metric and LT tires:

Standard Load (SL): 35 psi
Extra Load (XL): 41 psi

Light Truck
Load Range C (LRC): 50 psi
Load Range D (LRD): 65 psi
Load Range E (LRE): 80 psi

P-metric tires used on passenger cars are rated to carry 100% of the load indicated on the tire's sidewall. However, if the same P-metric tires are used on light trucks, (pickup trucks and sport utility vehicles for example), their carrying capacity is reduced to 91% of the load indicated on the tire's sidewall. This reduction in load results in causing light truck vehicle manufacturers to select proportionately larger P-metric sized tires for their vehicles to help offset the forces and loads resulting from a light truck's higher center of gravity and increased possibility of being occasionally "overloaded."

For example, P235/75R15 P-metric sized, standard load tires used on cars and light trucks would be rated to carry the following maximum loads at 35 psi:

Cars - Full Value - 2028 lbs.
Light Trucks - 9% Reduced Value - 1845 lbs.

A tire’s load-carrying capacity can be indicated in several different ways. They are:

Load Index – a number between 0 and 279 corresponding to a maximum load in lbs. Most often seen in P-metric and LT-metric radial tires.

Load Rating – a single letter between A and F indicating a tire’s RELATIVE load-carrying capacity i.e. the letter does not correspond to an exact capacity or even range of capacities. All we can tell is that an E rated tire will have a greater capacity (and therefore presumably a more rugged construction / possibly stronger sidewall ) than a C rated tire.

Ply Rating – an even number between 2 and 12, this is an older system, identical to the alphabetic load rating system, and having NOTHING to do with the actual number of plies in a tire’s construction i.e. a 10-ply rated tire could be made from a single ply. This is misunderstood and misused all the time. The key to avoiding confusion is to always make sure you use the words “ply rating” when referring to the load carrying capacity of a tire. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric body plies.

Specific Load / Sidewall Imprint – max load and pressure spelled out on the sidewall. E.g. “Max load 1250 lbs at max pressure 30psi cold”. When shopping for tires where actual load capacity is a concern (e.g. for your tow rig) this is the best system to use.

Note that neither the Load Rating nor Ply Rating systems correspond to exact load numbers. In fact, depending on manufacturer, size, construction, single- or dual-configuration, etc. tires with the same load range or ply rating can have widely varying actual load-carrying capacities. For example, from various charts, I have seen the following ranges (note the overlap):

B - 1100-1520 lbs
C - 1765-2205 lbs
D – 1930-3000 lbs
E - 2470-3042 lbs
F – 3415-5205 lbs
G – 3415-6610 lbs
H – 4806-7830 lbs

Rather, the Load rating and Ply rating systems are useful only for relative comparison between tires. For example, all we can really tell is that an E rated tire will have a greater capacity (and therefore presumably a more rugged construction / possibly stronger sidewall ) than a C rated tire.

Here is a chart of common Load Index numbers:

Tire Load Index (number) and Load Capacity (lbs.)

Index Load Index Load Index Load Index Load Index Load
0 99 30 234 60 551 90 1323 120 3086
1 102 31 240 61 567 91 1356 121 3197
2 105 32 247 62 584 92 1389 122 3307
3 107 33 254 63 600 93 1433 123 3417
4 110 34 260 64 617 94 1477 124 3527
5 114 35 267 65 639 95 1521 125 3638
6 117 36 276 66 661 96 1565 126 3748
7 120 37 282 67 677 97 1609 127 3858
8 123 38 291 68 694 98 1653 128 3968
9 128 39 300 69 716 99 1709 129 4079
10 132 40 309 70 739 100 1764 130 4189
11 136 41 320 71 761 101 1819 131 4299
12 139 42 331 72 783 102 1874 132 4409
13 143 43 342 73 805 103 1929 133 4541
14 148 44 353 74 827 104 1984 134 4674
15 152 45 364 75 852 105 2039 135 4806
16 157 46 375 76 882 106 2094 136 4938
17 161 47 386 77 908 107 2149 137 5071
18 165 48 397 78 937 108 2205 138 5203
19 171 49 408 79 963 109 2271 139 5357
20 176 50 419 80 992 110 2337 140 5512
21 182 51 430 81 1019 111 2403 141 5677
22 187 52 441 82 1047 112 2469 142 5842
23 193 53 454 83 1074 113 2535 143 6008
24 198 54 467 84 1102 114 2601 144 6173
25 204 55 481 85 1135 115 2679 145 6393
26 209 56 494 86 1168 116 2756 146 6614
27 215 57 507 87 1201 117 2833 147 6779
28 220 58 520 88 1235 118 2910 148 6944
29 227 59 536 89 1279 119 2998 149 7165
. . . . . . . . 150 7385

Here is a chart of Load Ranges, the corresponding Ply Rating, the approximate equivalent Load Index, approximate load carrying capacity, and nominal maximum inflation pressure. Note that the data is incomplete because these systems were never designed to readily interchange. And again, the figures in italics are APPROXIMATE and can vary widely in different tires.

Load Range Ply Rating

Load Index

Approximate Lbs/tire


A 2 92 1389  
B 4 98 1653 35
C 6 104 1984 50
D 8 110 2337 65
E 10 116 2756 80
F 12 122 3307 95
G 14     100-120
H 16     100-120
J 18      
L 20     125
M 22      
N 24      

Speed Rating

Most off-road tires are not speed rated, and most of us have no concern for a tire's speed rating because of the use our tires see. That said – no tire article would be complete without at least a mention of speed ratings – and they might be useful if you’re shopping for tow rig tires.
A tire’s speed rating indicates the maximum, sustained speed at which it can safely operate. Differences are based primarily on how much heat is generated in the tire. The faster you go, the more heat is generated, and heat breaks down the rubber in the tire. A tire’s speed rating will therefore depend on how much heat the tire builds at speed (based on its construction) and how well it can handle that heat (how much damage is done to the tire by the heat). A “Z” rated tire will not build much heat and the heat it will build will not damage it nearly as it would a “J” rated tire.

Speed ratings are usually indicated on the sidewall as a letter code, in combination with the numerical Load Index. This combination of speed and load data is known as the tire’s “Service Description”.



82 = the Load Index is 82 (or 1047 lbs)
S = the tire is rated for sustained operation up to 112 MPH

Here is a chart of Speed ratings:

A1 3 5 J 62 100
A2 6 10 K 68 110
A3 9 15 L 75 120
A4 12 20 M 81 130
A5 16 25 N 87 140
A6 19 30 P 93 150
A7 22 35 Q 99 160
A8 25 40 R 106 170
B 31 50 S 112 180
C 37 60 T 118 190
D 40 65 U 124 200
E 43 70 H 130 210
F 50 80 V 149 240
G 56 90 Z 149+ 240+
      W 168 270
      Y 186 300
      (Y) 186+ 300+

Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.
It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating, even after being repaired because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:

225/50SR16 225/50SR16 89S 225/50R16 89S

Early tires had their speed rating symbol shown "within" the tire size, such as 225/50SR16. Tires using this type of branding were made prior to 1991.

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S.

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

W 168 mph - 270 km/h
Y 186 mph - 300 km/h

While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h

Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h


Even the toughest tires aren't bulletproof. And if you run them hard enough for long enough - eventually you're going to have to deal with repairing one. Punctures in the tread are easy to fix - just plug them from the outside and add a nice big patch on the inside. Don't use the dinky little plugs and patches you get at auto parts stores - they're only meant for radial tires on a car. Instead, head to the local 18-wheeler or tractor supply house and get a heavy duty plug and patch kit intended for big trucks, off-road equipment, or tractors.

Sidewall damage is another thing altogether. It's what everybody dreads - and for good reason - it can be very difficult to repair. You can't simply plug or patch a sidewall gash - the flexing of the sidewall and the loads imposed on it will spit out a plug in short order. There is some hope however. The trick to a decent sidewall repair is something called a "section repair" that comes from the heavy truck and equipment tire world.

A ‘section repair’ is the term for a professional, industrial repair to a damaged tire. It is normally performed only on large heavy equipment type tires that cost many thousands of dollars. The damaged area is “sectioned” or cut out and the area enlarged – similar to the way you would cut out rusted sheet-metal. A new piece of rubber, or combination of rubber and body-ply is then vulcanized over the damaged area.

Technically, vulcanizing is the process of hardening rubber by combining it with either sulphur, selenium, or tellurium and applying heat. The end result is rubber with a useful level of hardness, but a sufficient amount of elasticity, or flexibility. The process was discovered accidentally by U.S. inventor Charles Goodyear in 1839 and patented in 1844. He named the process "vulcanizing" after Vulcan, the Roman God of fire.

Vulcanizing in the context of tire repair refers to a process where rubber is, essentially, 'welded' by the carefully controlled application of heat, to repair punctures or damage to the tire; using a machine called a vulcanizer.

There are also several types of “cold-cure”, “no-heat”, or "cold fusion" vulcanizing processes that can be used by either the professional or do-it-yourselfer. Generally, you grind out the damaged area, apply a large patch-like repair section (often called a “boot”) inside the tire and then apply some sort of cold vulcanizing chemical. After a prescribed amount of time (often up to 72 hours – depending on the manufacturer) the repair is chemically cured.

In most cases, radial tires are much less readily repaired using these methods, especially if the damage is to the sidewall, because of the risk of a blowout known as a “zipper”. Recall that all the chords in all the plies in a radial lie in the same direction. This means that a split or gash in the sidewall of a radial can quickly spread – like cutting a board with an axe along the grain, leading to sudden and explosive failure.

In fact, most tire manufacturers, along with the Rubber Manufacturers Association state that it is unsafe to repair (especially in a radial) a tire injury that is outside of the steel belts, or located on any part of the sidewall.

However, for a trail-only, off-road, bias ply tire a professional section repair can save the tire. Here are a few pics of just such a repair I had made to one of my 42" TSL's after a viciously sharp rock punctured the sidewall:

The injury - right in the sidewall of course!

A nasty little V-shaped cut. You can see the nylon chords in the body plies.


The section repair vulcanized to the tire.

It doesn't look pretty, but it works.

Close-up view - you can see the ends of nylon chords in the repair section.

View of the repair from the inside.

How to Read the Sidewall

There's an awful lot of useful information that is moulded into the sidewall of every tire:

The most useful of which are as follows:

Service Type

Most tire sizes begin with a letter or letters that identify the type of vehicle and/or type of service for which they were designed. The common indicators are as follows:

P225/50R16 91S

P = When a tire size begins with a "P," it signifies the tire is a "P-metric" size that was designed to be fitted on vehicles that are primarily used as passenger vehicles. This includes cars, minivans, sport utility vehicles and light duty pickup trucks (typically 1/4- and 1/2-ton load capacity). The use of P-metric sizes began in the late 1970s and they are the most frequently used type of tire size today.

225/50R16 92S

If there isn't a letter preceding the three-digit numeric portion of a tire size, it signifies the tire is a "Metric" size (also called "Euro-metric" because these sizes originated in Europe). While Metric tire sizes are primarily used on European cars, they are also used on vans and sport utility vehicles. Euro-metric sizes are dimensionally equivalent to P-metric sizes, but typically differ subtly in load carrying capabilities.

T125/90D16 98M

T = If a tire size begins with a "T," it signifies the tire is a "Temporary Spare" ("space saver" or "mini spare") that was designed to be used temporarily only until a flat tire can be repaired or replaced.

LT245/75R16 108/104S

LT = If a tire size begins with "LT," it signifies the tire is a "Light Truck-metric" size that was designed to be used on vehicles that are capable of carrying heavy cargo or towing large trailers. This includes medium and heavy-duty (typically 3/4- and 1-ton load capacity) pickup trucks, sport utility vehicles and full-size vans. Tires branded with the "LT" designation are designed to provide substantial reserve capacity to accept the additional stresses of carrying heavy cargo.

7.50R16LT 112/107Q, 8.75R16.5LT 104/100Q or 31x10.50R15LT 109Q

LT = If a tire ends with "LT," it signifies the tire is an earlier Light Truck size designed to be used on vehicles that are capable of carrying heavy cargo and towing trailers or are wider, oversized tires designed to help the vehicle drive on top of loose dirt or sandy surfaces. This includes light, medium and heavy-duty (typically 1/2-, 3/4 and 1-ton load capacity) pickup trucks and sport utility vehicles. Tires branded with the "LT" at the end of their size designation are designed to provide substantial reserve capacity to accept the additional stresses of carrying heavy cargo.

195/70R15C 104/102R

C = If a Euro-metric sized tire ends with a "C," it signifies the tire is a "Commercial" tire intended to be used on vans or delivery trucks that are capable of carrying heavy loads. In addition to being branded with the "C" in their size, these tires are also branded with their appropriate Service Description and "Load Range" (Load Range B, Load Range C or Load Range D).


ST = If a tire size begins with "ST," it signifies the tire is a "Special Trailer Service" size that was designed to only be used on boat, car or utility trailers. ST-sized tires should never be used on cars, vans or light trucks. Trailer tires have extra strong sidewalls to stand up to the side-side motion of a trailer but not for the loads applied to, or the traction required by, drive or steering axles.

Section Width

Following the letter(s) that identify the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.

P225/50R16 91S

The 225 indicates this tire is 225 millimeters across from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted and measured on a specified width wheel. This measurement is also referred to as the tire's section width. Because many people think of measurements in inches, the 225mm can be converted to inches by dividing the section width in millimeters by 25.4 (the number of millimeters per inch). 225mm / 25.4 = 8.86"

Sidewall Aspect Ratio

Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

P225/50R16 91S

The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the shorter the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we calculate that this tire size results in a tire section height of 4.43".

Internal Construction

A letter (R in this case) that identifies the tire's internal construction follows the two digits used to identify the aspect ratio.

P225/50R16, P225/50ZR16

The R in the P225/50R16 91S size identifies that the tire has a radial construction in which the tire's body plies "radiate" out from the centerline of the tire. Radial tires are by far the most popular type of tire today representing over 98% of all tires sold.

If the R in the size was replaced with a D (225/50D16), it would identify that the internal tire body plies crisscross on a Diagonal and that the tire has a bias ply construction.

If the R in the size was replaced with a B (225/50B16), it would identify that the tire body plies not only crisscross the tire on a diagonal, but that they are reinforced with belts under the tread area. This type of tire construction is called "Bias Belted."

Speed Rating

Today, the only tires that continue to include the speed rating "in" the tire size (P225/50ZR16) are Z-speed rated tires. In this case, following the two digits used to identify the aspect ratio are the letters ZR to identify the tire's speed rating (Z) and its internal construction (R). Since 1991, all other speed ratings are identified in the tire's Service Description (see below).

Tire and Wheel Diameter

P225/50R16 91S

The 16 indicates the tire and wheel diameter designed to be matched together.

Tires that have a rim diameter expressed in inches (P225/50R16, as well as 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 26 and 28) are called "inch rim" sizes, are the most common type of tire size and are used on most cars, minivans, vans, sport utility vehicles and light duty light trucks.

While not as common, two additional "unique" types of tire/wheel diameters are still in use today.

Tires and wheels that have a rim diameter expressed in "half" inches (8.00R16.5LT, as well as, 14.5, 15.5, 17.5 and 19.5) are used on some heavy-duty trailers, heavy-duty light trucks and box vans.

Tires and wheels that have a rim diameter expressed in millimeters (190/65R390, as well as, 365 and 415) are called millimetric sizes. Michelin initiated millimetric sizes for their TRX tires that saw limited use on many different car models in the late 1970s and 1980s.
Michelin PAX System run flat tires have been introduced as an integrated wheel/tire system on a very limited basis as Original Equipment (O.E.) in North America. An example PAX System size of 235/710R460A 104T expresses tire and wheel dimensions in millimeters (235 mm Section Width, tire Overall Diameter of 710 mm and a 460A mm rim diameter, with the "A" in 460A signifying these tires feature “asymmetric” beads in which the outside bead (450 mm) and inside bead (470 mm) are actually different diameters.

All of these "unique" tire/wheel diameters were developed specifically because the tire and wheel design or intended vehicle use required them to be different than conventional tires and wheels. All of these tires and wheels feature bead profiles that have a different shape than traditional "inch rim" sizes.

Tires and wheels with unique rim diameters should never be combined with traditional "inch rim" tires and wheels.
It is critical that the tire and wheel diameters are always confirmed to match before the tire is mounted on the wheel.

Service Description

P225/50R16 91S

The 91S represents the tire's Service Description. A Service Description identifies the tire's Load Index and Speed Rating. Service Descriptions are required on all speed rated (except for Z-speed rated) tires manufactured since 1991. For more information on Load Index and Speed Rating see he individual sections in this article.

Load Range

LT245/75R-16E, 7.50R-15D, 31x10.50R-15C, ST205/75R15 LRC

If a tire does not use the Service Description on the sidewall, it’s load range will be indicated as part of the tire’s description, as shown in the above examples, using the Load Rating letter designation system described earlier in this article.


LT255/70R16 XL M+S

XL or RF designates an Extra Load or Reinforced tire. If not specified, Standard Load (SL) is assumed and will usually not be labeled as such.

M+S designates a tire rated for mud and snow use.

"MAX LOAD SINGLE 2623 lbs. at 65 psi COLD"

This indicates the maximum load rating of the tire and corresponding minimum cold inflation pressure.
Note that P and LT tires are often rated slightly different. If P-rated tire is used in an LT application, you need to de-rate the sidewall load capacity by 9% - 10% according to many tire makers.

The branding on the sidewall of a tire is required to list the materials and number of layers of each material used to reinforce the rubber.
A typical tire's basic construction materials are usually presented as follows:


The branding in this example identifies that molded into the rubber under the centerline of the tread lies two radial body plies of polyester cord, two belts of angled steel cord and one circumferential cap ply of nylon cord. It also identifies that in each sidewall at the widest points between the tire's inner and outer sidewalls (tire section width) lie two radial body plies of polyester cord (a continuation of the same two body plies that were listed under the centerline of the tread).

Tire FAQ

What’s the best way to replace a single tire or pair of tires on a vehicle?

  • Never mix radial and bias ply tires on the same axle (because of their different handling characteristics discussed earlier in this article)
  • If you have radials on one axle and bias ply on another, run the radials on the rear
  • If you are replacing a pair of tires, put the new ones on the rear
  • If you have to replace just one tire, pair the new one with the best of the other three and run them on the rear

What is the maximum weight it should take to balance my tire?

The industry standard is approx. 2% of the tire weight. So, because a 42” TSL weighs about 100lbs, 2% is 2lbs or 32ozs of lead! That’s industry standard. Keep this in mind next time you’re wondering why your 42” Swampers don’t balance well - it’s not because of the quality of the tire – it’s because it weighs so much – it’s just the physics of dynamically balancing that much rolling mass – and it’s the price you must pay for large, aggressive tires.

What are tires made of?

The average steel-belted radial tire is made up of:

  • 28% Carbon Black
  • 27% Synthetic Rubber
  • 14% Natural Rubber
  • 10% Steel Wire
  • 10% Extender Oil
  • 4% Organic Fiber
  • 4% Other Petroleum Products
  • 3% (S, ZnO, Ti02, etc...)

How round is round?

Generally, a passenger-car tire is considered round if it has less than 0.030" radial or lateral runout. An LT tire is considered round if it has less than 0.060" radial and lateral runout.

Does it matter how I mount the tire on the rim?

There are two schools of thought on this.

The first has that you should mount the high-spot of the tire (often indicated by a red dot) aligned with the low-spot of the rim (often the valve hole, but may be separately indicated, depending on the wheel in question).

The other method is to mount the lightest spot of the tire (often indicated by a yellow dot) aligned with the heaviest spot on the rim (the valve).

What effect do different rim widths have on my tires?

The wider the rim, the greater the section width. Section width increases about 0.4” for each additional inch of rim width (and vice versa).

A wider rim increases the distance between the beads, which results in a straighter sidewall, which stiffens it. The straighter sidewall also exposes the rim, making the wheel more susceptible to damage.

A narrower rim pulls the beads closer together, curving the sidewalls. This increased curvature allows the sidewall to flex more readily. It can also help with bead retention at lower air pressures, although using narrow rims is no substitute for beadlocks.

Why do race teams use Nitrogen in their tires instead of air?

Race cars, aircraft, and other ultra-high performance machines use Nitrogen in their tires instead of air because, when heated or cooled, nitrogen has a much more consistent rate of expansion and contraction than air.
This is because air contains varying amounts of moisture due to changes in the relative humidity. This water vapour causes air to be inconsistent in its rate of expansion and contraction.

What is the difference between an LT and P tire of the same size?

LT tires that are load range C or greater tend to be rougher riding and noisier than their P-Metric counterparts and more expensive since the LTR size equivalent to the P-Metric has heavier body ply construction and the tread lugs are generally more aggressive.

P and LT tires are also often rated slightly differently. If P-rated tire is used in an LT application, you need to de-rate the sidewall load capacity by 9% - 10%.

How should I store unmounted tires?

  • Store them on their sides in a clean, cool, dry, dark, and well-ventilated area (but with a minimum of circulating air).
  • Keep them out of direct sunlight.
  • Keep them away from sources of ozone such as operating welders and electric motors. Store tires away from the furnace, sump pump, power tools, etc.
  • If you must stack them, do so only to a height where the bottom tire retains its shape, usually no more than four high.

What about tires on my rig in storage?

  • Store the vehicle on blocks to remove all weight from the tires.
  • If the vehicle cannot be blocked up, completely unload it so minimum weight will rest on the tires. The surface should be firm, reasonably level, well drained, and clean.
  • Keep tires inflated to recommended operating pressure.
  • Move the vehicle at least every three months to prevent ozone cracking in the bulge area, to help maintain oil dispersion within the rubber compounds, and to prevent a "flat spot" from developing.

What’s so special about “ST” tires for my trailer? Why can’t I replace them with P tires with an equivalent load rating?

“ST” or “Special Trailer” tires are designed specifically for trailer service, whether they are radial or bias ply. They feature materials and construction to meet the higher load requirements and unique demands of trailering. For example, ST tires are constructed for better high speed durability and bruise resistance under heavy loads and they have stiffer sidewalls that help to reduce trailer sway. Passenger car (P) or light truck (LT) tires do not have the structural components to provide stability and handle the stress and dynamics imposed by a trailered load.

ST tires typically have larger chords in the body plies and the steel wire in the beads has a larger diameter and greater tensile strength to meet the additional load requirements. ST tire rubber compounds also contain more chemicals to resist weather and ozone cracking.

Similarly, trailer tires are designed for use on trailer axle positions only, not for the loads applied to, or the traction required by, drive or steering axles.

Are there special considerations with trailer tires that are not present with other tires?

While the majority of the following factors also apply to other tires, they have special significance for trailer tires. There are two main reasons for this. First, absolutely nothing good happens when you experience a tire failure while towing a heavy load. A blowout in your car during the morning commute is bad enough – but when it happens as you’re towing 4 tons at 70mph in the dark on a curvy, rain-slick road the stakes are incredibly high! Secondly, trailer tires tend to get used, abused, and neglected or forgotten about. Because we don’t use them every day and because there’s nothing sexy about them we tend to take them for granted and not pay them the attention they deserve. We do so at our own peril!

· Always inflate trailer tires to the maximum inflation indicated on the sidewall.
· Check inflation when the tires are cool and have not been exposed to the sun.
· If the tires are hot to the touch from operation, add 3 psi to the max inflation.
· Underinflation is the number 1 cause of trailer tire failure.
· Tires lose approximately 1 psi per month as well as 1 psi for every 10-degree drop in temperature.

Load Carrying Capacity
· All tires must be identical in size for the tires to properly manage the weight of the trailer.
· The combined capacity of the tires must equal or exceed the GVW of the axle.
· The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent. If the actual weight is not available, use the trailer GVW
· If a tire fails on a tandem axle trailer, you should replace both tires on that side. The remaining tire was likely subjected to excessive loading.
· If tires are replaced with tires of larger diameter, the tongue height may need to be adjusted to maintain proper weight distribution.
· One key to extending tire life on a tandem- or tri-axle trailer is to ensure that the trailer is riding level, thus distributing the load equally among all the tires. If the trailer tongue sits too high, the rear tires may bear the brunt of the load: with the trailer tongue too low, the front tires may be unduly stressed.

· All "ST" tires have a maximum speed rating of 65 mph.
· As heat builds up, the tire's structure starts to disintegrate and weaken.
· The load carrying capacity gradually decreases as the heat and stresses generated by higher speed increase.

· Time and the elements weaken a trailer tire. The structural components and bonding agents slowly break down. This is due primarily to internal air pressure forcing oxidation of the tire materials. Ultraviolet rays also attack the rubber on a tire left exposed to the sun. As a result, a 15-year-old tire that was rarely used may look virtually new, but because of the ravages of time and elements, it does not have the same strength as when it was new.
· In about 3 years roughly one third of the tire's strength is gone.
· Three to five years is the projected life of a normal trailer tire.
· It is suggested that trailer tires be replaced after 3 to 4 years of service regardless of tread depth or tire appearance.

· Trailer tires are not designed to wear out.
· The life of a trailer tire is limited by time and duty cycle.
· The mileage expectation of a trailer tire would be 5,000 to 12,000 miles.

· The ideal storage is in a cool, dark garage at maximum inflation.
· Use tire covers to protect the tires from direct sunlight.
· Use thin plywood sections between the tire and the pavement.
· For long term storage: Put the trailer on blocks to take the weight off the tires, lower the air pressure and cover tires to protect from direct sunlight.

Should I use Radial or Bias Ply tires for my trailer?

It used to be that bias ply tires were considered the only way to go for trailer tires, because their sidewalls are stronger and stiffer than those of radial tires. However, recently radial ST tires have gained widespread acceptance. Both can do the job well, but there are differences. The bias ply tires will still have stiffer sidewalls and therefore be more resistant to trailer sway and so provide more lateral stability. The downside is that a bias ply tire will run significantly hotter than a radial (for reasons discussed earlier in the article). And we know that heat is one of the main enemies of any tire. Which to run is a matter of choice. Some will say that it depends on your towing habits – that you should use a bias ply for towing heavy loads because of the extra measure of stability; and that you should use a radial if you tow light loads at high speeds for long distances, because they run significantly cooler.

Of course, nobody ever defines what a “heavy” load is – is it 5000lbs, 10,000lbs or more?

I have run both radial and bias ply on my 7000lb trailer and can attest that, after 6 hours of towing at 65mph, the bias ply tires are hot to the touch while the radials are cool.

With proper trailer/axle weight rating, loading, tongue weight, type of hitch, trailer brakes, and size/weight of tow rig I don’t feel that sway and stability are a problem and so my personal preference, towing 7000lbs of trailer and buggy, is to run radials because the cooler the tire – the less it will fatigue. Your trailer, load, and needs may lead you to decide that bias ply are a better choice – especially if you have issues with trailer sway.

Do I have to run my trailer tires at Max PSI all the time?

The safest answer is yes, and many manufacturers will state this. However, some believe that IF (and ONLY if) you know the exact weight of your loaded trailer you can achieve a marginally softer ride by inflating the tires to less than the maximum pressure, using a load vs pressure chart for your specific tires. I wouldn't do it myself, but such a chart will look something like this:

Trailer Tire Load Limits (in lbs.) at Various Inflation Pressures

35 PSI

50 PSI

65 PSI

80 PSI


880 (B)

1100 (C)




990 (B)

1230 (C)




1100 (B)

1360 (C)




1200 (B)

1480 (C)




1320 (B)

1610 (C)




1430 (B)

1760 (C)

2040 (D)



1520 (B)

1870 (C)




1480 (B)

1820 (C)

2150 (D)



1760 (B)

2150 (C)

2540 (D)

2840 (E)


1820 (B)

2200 (C)

2600 (D)

2910 (E)


2090 (B)

2600 (C)

3000 (D)

3420 (E)

Super Swamper Weights

** Special thanks to MAD 4WD for providing this information on the Pirate4x4.com Forum **

Super Swamper TSL Radial

Size Ply Rating Approx Weight in lbs
LT225/85R15 6 34
LT215/85R15 6 34
30x10.50R15LT 6 47
31x9.50R15LT 6 45
32x10.50R15LT 6 51
33x10.50R15LT 6 53
33x12.50R15LT 6 55
36x12.50R15LT 6 64
36x14.50R15LT 6 79
38x15.50R15LT 6 89
LT265/80R16 8 54
33x12.50R16.5LT 10 62
36x12.50R16LT 10 70
36x14.50R16LT 10 84
36x14.50R16.5LT 10 84
38x15.50R16.5LT 10 95

Super Swamper Bias Ply TSL

Size Ply Rating Approx Weight in lbs
28x8.50-14LT 4 31
29x8.50-15LT 4 33
31x10.50-15LT 6 48
12-15LT 6 49
32x9.50-15LT 6 50
33x12.50-15LT 8 60
15/35-15LT 6 81
Q78-15LT 6 65
36x12.50-15LT 8 65
38x12.50-15LT 6 71
16/38.5-15LT 6 90
15/39.5-15LT 6 96
15/42-15LT 6 106
18.5/44-15LT 6 122
9/32-16LT 6 51
9/32-16LT 52 10 52
10/32-16LT 6 48
13/33-16LT 8 62
Q78-16LT 6 66
13/36-16LT 6 67
13/38-16LT 6 69
33x12.5-16.5LT 6 61
34x9.5-16.5LT 6 54
15/35-16.5LT 6 76
15/35-16.5LT 10 84
36x12.5-16.5LT 8 66
38x12.5-16.5LT 6 73
16/38.5-16.5LT 6 89
15/39.5-16.5LT 6 92
15/39.5-16.5LT 6 98
15/42-16.5LT 6 104
18.5/44-16.5LT 6 121

Super Swamper TSL / SX

Size Ply Rating Approx Weight in lbs
29x10.50-15LT 4 55
30x11.50-15LT 4 55
31x13.50-15LT 6 59
32x11.50-15LT 6 70
33x15.50-15LT 6 83
35x15.50-15LT 6 83
36x12.50-15LT 6 78
38x12.50-15LT 6 85
38.5x14.50-15LT 6 89
32x11.50-16LT 6 61
33x15.50-16.5LT 6 68
35x15.50-16.5LT 6 78
36x12.50-16.5LT 6 74
38x12.50-16.5LT 6 83
38x12.50-16.5LT 10 85
38.5x14.50-16.5LT 6 93

Glossary of Tire Terms:

Air Pressure:
The amount of air inside the tire pressing outward on each square inch of tire; expressed in pounds per square inch (psi).
A term for describing the size of a tire in which both letters of the alphabet and numbers are used.
A synthetic fabric used in some tires that is (pound-for-pound) stronger than steel.
Aspect Ratio:
The relationship of a tire's height to its width, expressed as a percent (%).
A round hoop of steel wires, wrapped or reinforced by ply cords, that is shaped to fit the rim; holds the tire onto the rim.
Belted Bias Tire:
A pneumatic tire with a body similar to that of bias tires, but which also includes two or more belts under the tread.
A special rubber-coated layer (or ply) of cords running circumferentially around the tire, located between the body plies and the tread. The cords may be made from steel, fiberglass, rayon, nylon, Kevlar, polyester or other fabrics.
They are designed to reinforce body plies to hold the tread flat on the road. Belts reduce squirm to improve tread wear and resist damage from impacts and penetration.
Bias Ply Tire:
A pneumatic tire in which the plies are laid at alternate angles less than 90 degrees to the center line of the tread. Plies usually run at angles about 30-40 degrees to the center line in a crisscross fashion.
AKA Casing. The main body of the tire, beneath the tread and sidewalls, consisting of wire beads and body plies. It forms the foundation for the tread and sidewalls.
Cold Inflation Pressure:
The amount of air pressure in a tire, measured in pounds per square inch (psi) before a tire has built up heat from driving.
The general term referring to the chemical formula for the tread material.
The strands of fabric forming the plies or layers of the tire. Cords may be made from fiberglass, rayon, nylon, polyester, Kevlar or steel.
DOT Markings:
A code molded into the sidewall of a tire signifying that the tire complies with U.S. Department of Transportation motor vehicle safety standards. The DOT code includes an alphanumeric designator which can also identify the tire's manufacturer, production plant, date of production and brand.
AKA Contact Patch. That portion of the tread that contacts the road.
The space between two adjacent tread ribs; also called tread grooves.
Inner liner:
A layer of specially compounded rubber forming the innermost layer of a tubeless tire, designed to inhibit loss of air pressure.
Loaded section height:
The height of the section of the tire that is making contact with the road.
Load Index:
An assigned number ranging from 0 to 279 that corresponds to the load carrying capacity of a tire.
Maximum Inflation Pressure:
The maximum air pressure to which a cold tire may be inflated; found molded onto the sidewall.
Nominal rim diameter:
The diameter of a tire rim.
Overall diameter:
The diameter of the inflated tire, mounted on the approved width rim, without any load.
Overall width:
The distance between the outside of the two sidewalls, including lettering and designs.
Uniform designation of tire sizes, in metric measurements originally introduced by American tire manufacturers in 1977; commonly called "P-metric series." A typical P-metric tire is P205/70R14 93S.
A layer of heat and impact resistant rubber-coated fabric containing cords that run parallel to each other; extends from bead to bead and goes between the inner liner and belts or tread; used to form the body of the tire. Automobile and light truck tire plies are normally constructed of nylon or polyester cords.
Radial Tire:
A type of tire with plies arranged so cords in the body run at 90 degree angles to the center line of the tread.
A metal support for a tubeless tire or a tire and tube assembly upon which the tire beads are seated.
Rim width:
Distance between the two opposite inside edges of the rim flanges.
Section height:
The distance from rim seat to outer tread surface of an unloaded tire.
Section width:
The linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs, raised lettering and decorations).
A numerical representation of a tire's aspect ratio; for example, 50 series Tires with the same aspect ratio, or relationship of height to width, are said to be the same “series”.
The area of a tire where the tread and sidewall meet.
Shoulder Blocks:
Raised rubber compound segments on the part of the tire tread nearest the sidewall.
That portion of a tire between the tread and the bead.
Special slits within a tread that increase wet and snow traction.
The process of introducing sipes (or slits) into the tread.
The combination of tire width, construction type, aspect ratio and rim size used in differentiating tires.
Speed Rating:
An alphabetical code (A-Z) assigned to a tire indicating the range of speeds at which the tire can carry a load under specified service conditions.
Steel Belt:
A belt material used in radial tires. Its high stiffness provides good handling and low tread wear.
A precisely engineered assembly of rubber, chemicals, fabric and metal designed to provide traction, cushion road shock and carry a load under varying conditions.
Tire Designation:
An alphanumeric code molded into the sidewall of the tire that describes the tire's size, including width, aspect ratio, rim diameter, load index and speed rating. Most designations use the P-Metric system.
That portion of a tire that comes into contact with the road. It is distinguished by the design of its ribs and grooves.
Tread Blocks:
Raised rubber compound segments on the outside visible part of a tire.
Tread Rib:
The tread section that runs around the circumference of the tire, separated by the tread grooves.
Tread wear Indicator:
Narrow bands, sometimes called "wear bars," that appear across the tread of the tire when only 2/32 inch of tread remains.
Tread width:
The width of a tire's tread that comes in contact with the road.
The friction between the tires and the road surface; the amount of grip provided.
(Uniform Tire Quality Grading Standards) A tire information system that provides consumers with ratings (from A to C) for a tire's traction and temperature. Tread wear is normally rated from 60 to 620. Ratings are determined by tire manufacturers using government-prescribed test procedures, and are moulded into the sidewall of the tire.
A device that lets air in or out of a tire. Fitted with a valve cap to keep out dirt and moisture and a valve core to prevent air from escaping.


Big, tough, proven, reliable, cool-looking, and great-performaing in all kinds of terrain. Any questions? Is the TSL still king? In my book it is - no question. In fact, there's only one tire that could ever steal me away from my 42" TSLs - and that would be a 42" TSL/SX!!



Interco Tire Corp
P.O. Box 6
Rayne, LA 70578-0006
Phone: 337-334-3814
Fax: 337-334-9796