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Old 09-28-2011, 02:29 AM   #1 (permalink)
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IFS/IRS why so bad off road?

Exactly how or why is independent suspension not so good off road? Many IFS/IRS setups can allow long wheel travel, yet they are still shunned for serious off road work in many cases (a few exceptions accepted).

But what's the theory/physics on why live axles are better?
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Old 09-28-2011, 04:19 AM   #2 (permalink)
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who said independent suspension was not good offroad?
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Old 09-28-2011, 04:40 AM   #3 (permalink)
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who said independent suspension was not good offroad?
Many.

For example Toyota marketed the 105 live axle version of the 100 Series Land Cruiser for this proclaimed reason.

And why do so many people do SAS's on lot of different IFS/IRS equipped trucks?

I'm not personally saying independent suspension isn't as good. I'm asking why do people say so, what are the real world off road limitations or even enhancements over live axles.
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Old 09-28-2011, 05:03 AM   #4 (permalink)
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One of the major limitations is flex. Then the CV joint's aren't all that strong. CV strength can be taken care of, at a cost though. With the amount of cost it's just cheaper to just go SAS.

Shhh don't tell Shannon Campbell though, he spanks many solid axle trucks.
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Old 09-28-2011, 05:18 AM   #5 (permalink)
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Originally Posted by 87JeepWrangler View Post
who said independent suspension was not good offroad?
are you kidding .................

search.....EVERYONE on this bourd said that ifs was not meant for off road and crawling untill koh came along and all the cool kids started doin it then all of the sudden its the next best thing since sliced bread.....bunch of fukin sheep...........

ive loved the idea of ifs and irs for years....i loved the evans crawler truck way back..........


now TTB is poping up.........how many of the sheeple on here condemed that...untill torchemate stepped up ....now everyone is in love with that idea....
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Old 09-28-2011, 05:21 AM   #6 (permalink)
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What kind of offroading are you talking about? Solid and independent both have advantages and disadvantages.

For the sand crowd and go fast desert stuff, independent certainly gets the nod. But the main issue is that travel is still the limiting factor for independent. Which is pretty much the only reason in an unlimited budget vehicle why you would still see a solid rear axle - they can still offer more travel. CV's can't quite keep up with the travel. I know there is some top secret mega dollar CV's out there that are getting some big angle numbers but this is for a very select few people.

For the high performance trail crowd, solid axles still work the best. Dollar for dollar, you can have a much longer travel suspension that is more durable. When speeds start slowing down, the benefits of IFS diminish quickly. You aren't likely to see a competitive cone dodger with independent suspension any time soon. It has been tried a few times. The solid axle allows for a degree of forced articulation from the left and right tire and ground clearance at the axle does not diminish when a wheel compresses. Higher unsprung weights also offer increased stability when the vehicle is at severe operating angles.
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Old 09-28-2011, 07:43 AM   #7 (permalink)
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The solid axle allows for a degree of forced articulation from the left and right tire and ground clearance at the axle does not diminish when a wheel compresses. Higher unsprung weights also offer increased stability when the vehicle is at severe operating angles.
At this point, these are the only downsides to IFS/IRS with the exception of cost.

Cost will come down soon too, but you can't beat the physics. Strength is a non issue anymore.
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Old 09-28-2011, 08:07 AM   #8 (permalink)
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What kind of offroading are you talking about? Solid and independent both have advantages and disadvantages.
I was thinking more trail, rocks, mudding type of thing. Something that requires flex.
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Old 09-28-2011, 08:08 AM   #9 (permalink)
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At this point, these are the only downsides to IFS/IRS with the exception of cost.

Cost will come down soon too, but you can't beat the physics. Strength is a non issue anymore.
Cost and strength are tied together. You can't have the needed strength with out a very high cost at this point in time.

Let's say I am building a full tube buggy and the cost of an ifs front or a 4 link 60 front.

ifs = $20-25k ?

4 link 60 = $8k ?
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Old 09-28-2011, 08:11 AM   #10 (permalink)
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At this point, these are the only downsides to IFS/IRS with the exception of cost.

Cost will come down soon too, but you can't beat the physics. Strength is a non issue anymore.
strength/$ is definitely an issue

you can't make a factory IFS perform reliably off road for the same $ as a comparably sized straight axle.
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Old 09-28-2011, 08:14 AM   #11 (permalink)
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Old 09-28-2011, 08:15 AM   #12 (permalink)
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I was thinking more trail, rocks, mudding type of thing. Something that requires flex.
Mud requires HP, big tires and a few missing teeth. As for trails and rocks, IFS has been proving itself for a few years now in Ultra4 and KOH events. Of course these set-ups are far from anything stock.
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Old 09-28-2011, 08:15 AM   #13 (permalink)
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Cost and strength are tied together. You can't have the needed strength with out a very high cost at this point in time.

Let's say I am building a full tube buggy and the cost of an ifs front or a 4 link 60 front.

ifs = $20-25k ?

4 link 60 = $8k ?
That 25 number includes brakes, r&p, lockers, spindles, shocks, and infrastructure (bulkhead), arms, and steering.


There's almost 10 grand in steering and shocks alone.
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Old 09-28-2011, 08:16 AM   #14 (permalink)
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Im not even sure he is referring to KOH/go fast IFS. I think he means OEM IFS....
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Old 09-28-2011, 08:24 AM   #15 (permalink)
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Im not even sure he is referring to KOH/go fast IFS. I think he means OEM IFS....
That's six letters that should not be used together
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Old 09-28-2011, 08:27 AM   #16 (permalink)
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But Good for him!

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Old 09-28-2011, 08:27 AM   #17 (permalink)
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That 25 number includes brakes, r&p, lockers, spindles, shocks, and infrastructure (bulkhead), arms, and steering.


There's almost 10 grand in steering and shocks alone.

My point exactly. A $4500 steering rack isn't exactly in everybody's budget. I consider that expensive.
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Old 09-28-2011, 08:28 AM   #18 (permalink)
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But Good for him!
maybe so, but it was immediately the first thought that came to mind when I saw the thread title, haha
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Old 09-28-2011, 08:34 AM   #19 (permalink)
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strength/$ is definitely an issue

you can't make a factory IFS perform reliably off road for the same $ as a comparably sized straight axle.
You have to in this type of case be very descriptive when you say "off-road" and "rocks". Speed/terrain is a very big deal when selecting on what to go with if your gonna dismiss the cost issues. There is a big difference in a 4 foot hole created by a rock and a 4" one. Try hitting a 4" rock at 120+ MPH with an IFS rig and then hit it with a SFA rig, you'll wish you had IFS at that point.

SCORE/Lucas trucks are off-road trucks. Even the 4wd trucks are IFS. Rears are almost all 4-linked. Same can be said with Desert trucks.

Most of the KOH/Ultra4 buggies are SA and see a very wide range of terrain. It's hard IMO to compare those to any other "off-road" rigs.

I think Campbell's IFS buggy(s) is/are a real exception here. Only 2 IIRC. I don't even want to think about the cost of his setup over a "standard" ultra4 SFA. Keep in mind campbell's setup isn't even close to being an "off-the-shelf" unit. IIRC it is 99% custom in-house made.

Then you got the tuff-truck type crowd. Most of those home built rigs in this area seem to be using TTB. Which I consider a cross between the two.

Mud trucks, well, it all depends on how much power your running. No flex issues there. For example a Toy 7.5" IFS unit is just not gonna hold a 400+ HP SBC engine but you can almost get a Toy 8" to handle it to some degree. Forget it if your running a BBC and 800-900 HP. Your not gonna find an IFS diff Toy or otherwise to handle that kinda of power. Well you might if you wanna run some sort of fabbed unit Similar to Power Block's BMW w/LS combo. And that's IRS anyway.
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Old 09-28-2011, 08:40 AM   #20 (permalink)
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My point exactly. A $4500 steering rack isn't exactly in everybody's budget. I consider that expensive.
We agree on that. My point is the 8k solid axle is just that. When you throw out the 25k IFS setup its fully loaded with a bunch of integrated parts that aren't included, but still necessary when you have a solid axle.

Still bank.

But if you want to ride like a cadillac over 2 footers at 85 mph, it costs.

3 years ago strength was out of reach for anything less than six figures. It's production parts now and the price will continue to come down.
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Old 09-28-2011, 08:53 AM   #21 (permalink)
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Im no expert here by any means, however, SA setups have been done and are readily available and have been for years and years. Even today alot of the really heavy duty vehicles out there are still using 1960's technology because it works. IFS and IRS have not been around as long and is just now getting popular with the offroad crowd in general. With that being said i think if you look at the broad spectrum of the "OFFROAD" world you will see that it really depends on 1 or 2 things.
1. if you wanna go fast, (desert, baja style etc.) go with IFS and IRS.
2. if you wanna go slower and are into rocks, mud or southern rock bouncing styles go with a SA.

3 THE EXCEPTION is KOH..... build what ever you want cause 9x out of 10 its gonna break before you get back to camp anyway and thats the fun part.

Again Im no expert. don't hate me cause im opinionated.
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Old 09-28-2011, 10:02 AM   #22 (permalink)
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takin this to JV for some "testing" this weekend...
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Old 09-28-2011, 10:13 AM   #23 (permalink)
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takin this to JV for some "testing" this weekend...
Stoked to see that rig finally ready for testing.....please update your build thread with some pics of both the finished rig and testing pics
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Old 09-28-2011, 11:03 AM   #24 (permalink)
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I believe an affordable, competitive, IFS assembly is possible. Yea the IFS parts can get expensive but is the whole front end really that much more than the solid parts? where are the differences?

IFS
you need
-8 heims and 4 uniballs. dont need the best stuff
-2000 for a pair of nice outer RCV's
-$700 for pair of 35sp 935's
(or spend about same price for 4 series 30 cv's)
-1500-$2000 for a 9' center with drive plates/bearing ($2500 for dutchman)
-pair of axle shafts
-ram would work fine for steering. dont need a rack

Unlike a solid axle you dont need ujoints. solids run bling outer joints too. (like rcv). solids still have links and need a total of 8 heims to run all the links.

in all reality the only price diff in hardware ammounts to the price of an extra set of cv's, and the 4 uniballs. a little more for the basic housing because the ifs housing has its own set of bearing and you need to buy those stub shafts. 2-3 thousand is the only difference. Thats chump change if one is building a competitive racer. And that is not a deal breaker if you are building a play toy for the weekends.

But the parts list doesn't show the whole picture. You can drop 10K in your fabricators wallet real fast. (worth every penny) The IFS front end is going to require a lot more cash because all these parts to date are one-offs and require a lot of pre-thought design and most of the ifs cars to date are spending money on fabrication. Unless someone has the time and skills to put it together right its going to get pricey. It doesn't have to be this way. Production jigged upright assemblies shouldn't cost more than $300-$400 a Pair. look at it. if you get rid of all the sexy weld washers and overkill gusseting the upright is nothing more than a cheap builder cup and 6 tabs. The Aarms would work fine if you built them from tube. there doesn't need to be any plate construction in any of the assembly. Its only a matter of time before we see a complete $8000 ifs assembly hit the market. you just weld it in and go fast with 15+ inches of travel


And campbell's car is not expensive. His engineering is not the best either. He uses good parts but doesn't throw money away on bling fabrication that doesn't make the car any faster. And he keeps the weight down. the guy is kicking everyones ass with a trackbar in back.
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Old 09-28-2011, 11:07 AM   #25 (permalink)
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(and maybee he can drive)
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