backspacing and bearing wear

I am in the process of determining what minor modifications will need to be made to fit either 32 or 33 inch tires onto my XJ, namely adjustments to backspacing, bumpstops, and fender/ wheel opening. I want to optimize my reduction in backspacing in order to minimize any increased stress on my bearings while at the same time achieving the clearance needed to prevent rubbing on my control arms.

Any increased frequency for having to change out the unit bearings in front is not a huge issue as changing these bearings is a pretty easy job, but changing the rear bearings is a bit more work. So I’m just wondering, does going to a wheel with reduced backspace result in the same increased wear on the rear bearings as on the front bearings as I would have assumed, or is it mainly just the front unit bearings that experience faster wear? Is there a difference in wear rates front to back?

I think you are over thinking this a bit. I have run 33's and now 35's on rims with 3.75" of back spacing along with wheel spacers on top of that. I have had the front hub bearings for over 2 years and zero issues. Before that I had the 33's and same rims without the spacers and still no issues.

You'd have to have very little backspacing or to adjust the steering stops a bit to avoid rubbing the control arms with a 12.5" wide tire.

I agree, I think your over thinking a bit.

Not trying to be rude at all, I've been running 37" iroks on 3.25" backspace wheels for a while now, flogging it and daily driving on who knows how old unit bearings. I'm not worried about it.

Also ran the same setup on another Xj for almost 3 years, never had to replace unit bearings, ball joints, axle bearings, nothing.

I wouldn't sweat it. Find some wheels you like and go for it

I've got 7 yrs and nearly 90k miles on unit bearings with 1.25" wheel adapters and 16x8 Moab wheels, running 285s (33) with a total of 4" BS with zero issues. I ran the same setup on my old jeep and put about the same amount of miles on that one with no issues

I think the front bearings have a harder life because they also contend with steering forces but less BS on rear wheels will also accelerate bearing wear.

I wouldn't make too many design decisions around it, though. Even if you have to replace a bearing set, you probably won't have the Jeep (or the Jeep's configuration) long enough to do it twice.

Regarding the rear axle, if you look a the position of the wheel in relation to the axle/wheel bearing (and everything else), you can see that the bearing supports virtually all of the load within the parameters of any reasonable backspacing. You could consider the carrier bearings to be "inner axle bearings" but they are so far removed from the wheel and the wheel bearing (fulcrum in this instance) that they carry little load. And they are relatively massive.

Thanks guys, these were all helpful responses.