Baystate Jeepers

I finally got the suspension done and the 35's mounted yesterday. Frank twisted my arm and made me test it out to see if everything worked well. So as soon as the last weld was done and the tires mounted we took her out for a test run. I thought everything worked well but when I got home I noticed that the front tires hit the springs, frame, rear of inner fender, and the shocks. I'm pretty sure I dont have the proper backspacing on the wheels. I'm pretty sure the ones I have are either 3.75 or 4 inch but I dont remember exactly.The question is, how much backspacing is needed when running 35's on a YJ? Any info would be appreciated. Thanks.

Usually 4" is optimal, with adjusted steering stops.

When you go under 4", you start getting out of the optimal relationship with the unit bearings - assuming stock axles. Also, you are increasing the scrub radius, which will result in accelerated ball joint and tire wear.
Chances are pretty good with 35s you'll need less back spacing or wider axles. That being said, I know a couple guys with YJs running d44 Grand Wagoneer axles, and they are running 5" back spaced wheels. The math doesn't add up, but these Jeeps have been built and wheeled hard for more than 10 years with no changes - and no body damage.

Mike : If I get what your saying ,His 3.5 or 3.75 should be good and only have to adjust the stops for the springs ? He has Kurts old 30 and 8.8 axles. We went spring over and used an add a leaf for slight arc. It leans to the left and that seems to be the side with the issues. He didnt feel the issues just looking after the run could you see the rub on the spring and touching of the inside rear of the inner fender. Not owning a YJ I wasnt sure if there were tricks we should learn. I can take care of the stops. Thanks FjR68

Basically, but 3.5 to 3.75" back space is harder on unit bearings and ball joints. But so are 35s, so it is what it is and steering stop adjustment should take care of it.

Ill try adjusting the stops and see how it goes. Thanks for the info.

KevinP wrote:Ill try adjusting the stops and see how it goes. Thanks for the info.

Sometimes, stacking washers behind the bolt heads will add a little umph to the bolts, to help prevent bending or breaking the bolts.

Thats a great idea, thanks.

Well , did you know if you lay a straight edge across the wheel and measure it to the mounting surface you would find the actual B S ? His are 4.25 not 3 anything . With a 35x12.5 tire its very close to everything. I think hes going to look for 5 rims under 4 in B S. Where is the target , he isnt to worried having to change unit bearing every year. We want to clear stuff to save the new tires from being sliced or chunked . Thanks FjR68

A straight edge minus the .25 lip the wheel weights clip to. The straight edge fits between the lips or you need to subtract the lips.

4" BS is best. 3.75" is ok, but less than optimal. 3.5" is getting pretty silly.
(Really, 4.5" - 5" BS is optimal, but not reasonable for over sized tires.)

The less back space you have, the more unit bearing and ball joint replacement you'l be doing.

Adjust the steering stops. Don't skip this simple step.

Mike : It was 4.25 from the rim not the lip. Thanks for the info. FjR68