Outer Limits 4x4 Board

Hi guys.
Need some desperate help on this one.
Was wheeling today with Nadim had 6 psi in those 36" Simex ET II
One of the tyres jumped off the wheel and wheel was slightly bent installed my spare tyres a 35" MTR Good year.....

When I engage my rear ARB the two rear tyres are not spinning in tandem.
It seems that when load is getting higher on the tyres one of them kind of slipps or stops spinning.

I identified three possiblites:

a- Tyre size difference a 36" on one side and a 35" on the other. 1" should not matter that much !!!
LinearVelocity = Angual velocityx Tyre Diameter
b-Air pressure too low causing tyre to slip on the wheel
c-damaged ARB side bearing


Appreciate your feeback on this one.

probably just as the axle twists and then releases. The axles will work like a torsional spring to a certain point.

The tyre size difference will not make any difference, because as far as I'm aware, an ARB air locker locks the two wheels together, end of story. There is no LSD effect, so in theory you could have a 36 on one side and a 26 on the other side, they should still both spin, just that the speed at the outermost point of the wheel will be different.

b) is a definite possibility - 6 psi sounds pretty damn low, especially if the tyre is getting a good bite into the surface.

A damaged side bearing (assuming you mean the carrier main bearings) would be noisy, but it wouldn't stop your wheels spinning, for the same reason as the tyre size difference - your axles are locked together, there is no possible way for it to slip, both hubs MUST spin at the same speed.

The only other thing I could think of is that your locker isn't engaging fully, and it keeps unlocking under load, but I don't know that this is really possible either, I'd have to look at a diagram of the internals again to work it out.

Slunnie

i thought of the maxi axles twisting and I know they do twist but I was on snow which has low traction effect.

Ranging Rover

Re the two diiferent tyre sizes, the ARB will spn the two axles at the same speed but when you have different tyre diameter.
Think of it as :
v1/36" = v2/34" = W

W being the angualr velocity of the axles spineed by the ARB locker.

the only other possiblity is that the ARB is not fully engaging.
I will try it out today in the after noon....but I gotta find a steep hill nearby as it is all city like where I live.

Jay

Re the two diiferent tyre sizes, the ARB will spn the two axles at the same speed but when you have different tyre diameter.
Think of it as :
v1/36" = v2/34" = W

W being the angualr velocity of the axles spineed by the ARB locker.

Yes, the actual tread of your tyres will spin at slightly different speeds, but I would assume you are really spinning the things to allow them to clear the treads, especially since you say under higher load. In this case, they should both spin, even if one is an inch smaller.

It seems that when load is getting higher on the tyres one of them kind of slipps or stops spinning.

That sentence there, in itself would suggest proof that it isn't the difference in tyre size - if the load is low (revs presumably low) then this is when one wheel would be at driving speed, and the other at wheelspin, then when the throttle and load is increased, the slower wheel would begin to spin.

I'd go either with the locker not fully engaging, or your tyre pressures too low - and I'd probably try pumping the tyre up to about 15 psi first, and see what happens.

the way i understand it is you could run for example a 32" tyre on one side and a 35" on the other to get you home,so long as the hub centre heights are equal distances off the ground.By inflating the 32" tyre or deflating the 35" tyre you'd get it right.Something to try anyway.

I tried the truck yesterday with the 2 similar tyres in back....
everything running ok.

I think the tyre difference is what caused the problem.

It seems that with an open diff running 2 different sized tyres will cause damage at highway speeds

Did you flick the swith on the move or at a standstill? If at rest, I'd say yep theres a problem.

The ARB doesn't use much force to engage. I think if buggered you can blow (suck?) down the lines to operate it, a bit like maxidrive. Does it follow that it doesn't need much opposing force to keep it out?

If on the move, the locker hasn't a hope of engaging. With a bit of windup in there it'll never engage. An open diff isn't 100% efficient, there's probably enough drag & friction to wind things up a bit.

Even at rest difflocks don't always engage. Isn't it springloaded to drop in once everything is freed up & lined up?

Regards
Max P