Need some help understanding rim backspacing as it pertains to wheel bearing loads. As I understand it the factory 8" wide rim has 5.71" between the mounting pad and the back lip of the rim, leaving 2.29" to the front of the rim. However most aftermarket, 9" wide, rims have 4.5" backspacing. I’ve read this can cause bearing failure because of the way the new rims load the bearings, right? As I see it, if the mounting pad is centered on the rim the natural balance of the rim and tire is retained. Also with a centered rim neither the inner nor outer side of the rim has a "lever arm" advantage. So in both cases it seems like an aftermarket, 0 offset rim would prevent bearing failure, not cause it. What am I missing?

 

I have minimal off set wheels for my baja. it makes no difference in balancing or bearing wear far as I know. it helps with tire spacing from the suspension/ steering/ inner fender areas. I have minimal ( zero) off sets on my vw baja to allow me the use of 31" tires and not rub the rear tortion (axle). so my wheels were pushed out like 3" to 4" from the hub.

I do not understand the theory behind "I’ve read this can cause bearing failure because of the way the new rims load the bearings, right?" it makes no sense when the wheel/ tire combination should be properly balanced prior to use.

 

I'm not talking about rotational balance. And for the sake of the discussion, lets omit "fitment". What I’ve read is that an aftermarket wheel pushes the wheel/tire out further than the factory wheel, and that can cause wheel bearing failure. Isn’t it more accurate to say the factory wheel is too far in and the aftermarket corrects that?

 

73Jim-

I understand what you are saying and fully agree with your statements... I would also agree that getting a wheel with a 0 offset would ultimately be the best for bearing wear. I guess the people who would say that a wheel with less backspacing will cause bearing failure earlier, must not be considering the leverage by thehalf of the wheel stickingtowards the truck.

I'm obviously no genious though... maybe you want a wheel that has a center line that is as close to centered with the center line of the wheel bearing??

 

I read this, and now, not only am i lost, i have a headache

 

it has to do with the steering axis inclination and the camber line,and where the cross.basically steering axis inclination is a straight line through the upper and lower ball joints then the camber line is a line down the center line of the tire and wheel combo and where they cross with relation with the road surface. ideally you want them to cross at the road surface but thing like tire size and wheel offset and backspacing can alter the camber line and affect tire wear bearing wear and handling.

 

^^^ hmm... I'd like to see that draw out as some sort of a picture, I bet it would be very interesting.

 

not a very good pic but it is the first one i could find

 

I think the information that you are posting does not apply to a vehicle with a straight axle like ours, I think it is talking about a vehicle with IFS?

 

What is the factory camber on these trucks? It something negative, right? If it is negative the "lever arm" of the factory wheel has more of an impact because of the backspacing. So your saying the backspacing is sort of a preload on the knuckle?