what'll break first, a ? for physics majors.

[Neal'88yj]

I was wondering if I took a pair of 35x 15.5 sx's
or the 36x12.5 sx's which would last the longest on my front d30?

would the added wieght of the 15.5's width be enough to equal the diameter of the 36s?

just curious.

[Imkunfused]

Thats like asking what came first.. a chicken or an egg..


It all depends on driving style and what your set up it.. Ive seen d30 welded hold up to 38.5x14.5 sx's.. Never broke a shaft, and wheeled the piss out of it.. and that was with the 260 joints..

He's on the board as 1lrgyj if you dont believe me

[Neal'88yj]

regardless of the driving style (I didn't ask IF it would break) there has to be some physics guy who knows a formula or wheeler who's tried this.

[Imkunfused]

its called rotating mass.. dont need to be a physics major to know that.. the heavier of the tire will put more stress on the axle.. most likely the 15.5 tire is a hell of a lot heavier than the 12.5.. so you do the math

[Neal'88yj]

Originally posted by ImKuNfusED
its called rotating mass.. dont need to be a physics major to know that.. the heavier of the tire will put more stress on the axle.. most likely the 15.5 tire is a hell of a lot heavier than the 12.5.. so you do the math

Right but the 36 has more diameter thus producing more torque against the axle ( like using a cheater bar).

[Imkunfused]

your talking about 1 inch.. and thats not ever true, because most tires never run the same.. the 35x15.5 will have more weight out at the end than the 36 x12.50.. Say you have a 250 lb man pushing on a breaker bar 35 inches from the nut.. and you have a 200 lb man pushing on a breaker bar 36 inches from the nut.. who will break the nut first..

Of course the 250 lb man, because he actually has more potential energy than the 200 lb man 1 inch further out

[JohnnyJ]

I'd pick the tall & skinny over short and fat.

A friend has been running 36x12.5 SXs for a couple of years on his D30 with ez-locker and it's held up so far. Not optimal, but spare shafts (and axles) are cheap and plentiful around here.

[JEEPRZ]

12.5s will be easier on the bearings and brakes as well

[1988YJ]

It really boils down to your wheeling style. I blew out RD44's on 37's until I went to Warns and CTM's. If you crank your tires and bounce your axles and take the most challenging lines you'll have the opportunity to have a cool one... after your axles are changed. If you take it easy and keep a smooth driving style, geared low and not hellbent to get it awn you'll have no problems The lighter tires will be the least stress on the axles, driving style will be the biggest stress.

[Goat]

It's actually 1/2" because torque is a moment arm...which uses radius not diameter. This is discounting rolling radius, which is smaller then the tire radius.

[Cheg]

Not a physics major but i did take a few classes

Don't forget the higher friction coefficient of the wider tires. Remember if your tires don't break loose under power, your ujoints might

[embro]

take that money and upgrade your axle... you dont want to learn the hard way.

[flexjeep]

Its all about the torque, the wider tire wont produce that much more of a friction force because the "normal force" (weight of the vehicle) is distrubuted over a larger area. Also when your rock crawling most of the time only a small portion of your tire is actually in contact with the rock. That 1/2 inch larger wheel radius will have a much bigger effect then some people seem to think, refering to the none sence above about the 200lb vs. 250lb man. The weight of the tire is very small compared to the weight of the vehicle and the ft-lbs of torque the vehicle is able to produce to the axles (this is a lot lot more then what the engine produces becuase of the gear reduction). Without getting too technical Its more like a 7,000 lb man trying to twist your axle while its fixed in place at 18 inches away compared to a 7,050lb man doing the same thing but only 17.5 inches away. The force on the axle due to the 1/2 inch is much greater then the extra 50lbs of force from the weight of the tire. Figuring out the exact difference of stress put on the axle between the two situations requires a strong grasp of calculus because shear strength of a cylindrical shaped object is involved. I will say this though, depending on the situation your in when your wheeling, that half an inch could be 10,000 lbs of force or more put on your axles. I won't bore you guys anymore. My .02.

[bigdude]

I ran 36x12.50 SXs with my D30 and after 3 months swapped 1-tons because it broke axles so often. I swear my 38x12.5 TSLs were lighter than those SXs, Krawlers heavier then both.