nclehmann

I want to mount 35s on 17" steeliies. The steelies I've been looking at are 17x8 with 4.5" of backspacing. Although most lifts recommend a minimum of 4.5" backspacing, they don't specify what the wheel width is. I assume the minimum backspacing requirement is to clear suspension and steering components (sway bar links, coils, steering knuckles, etc).

A backspacing of 4.5" on an 8" width wheel is the same as 5" on a 9" width wheel, which I think is the most common width for running 35/12.50s.

Has anyone running 17x8 wheels with 35/12.50 tires had any rubbing issues? Should I get 17x9 instead?

08RUBIJK

4.5" = 4.5"...

Backspacing is the measurement from the wheel mounting surface to the back edge of the rim - so if the rim lists a backspacing of 4.5", that is the same regardless of the rim width.

You are confusing offset with backspacing.

nclehmann

I don't think so. Backspacing is the distance between the rim edge on the inside of the wheel to the mounting pad of the wheel (the part that actually mounts to the studs.

On a 17x8 wheel, the centerline of the wheel is at 4". With a 4.5" backspacing, the center of the tire will be 0.5" further in (towards the Jeep) than the mounting plate.

On a 17x9 wheel, the centerline of the wheel is at 4.5". With a 4.5" backspacing, the center of the tire will be at the mounting plate - further out from the Jeep than with an 8" width wheel.

Therefore, in effect, the outside edge of the tire will sit 0.5" further out with a 17x9 wheel than with a 17x8 wheel if both have 4.5" of backspacing.

JK^2

Nah, you really are confusing backspacing and offset. an 8" rim with 4.5" backspacing will stick out an inch less than a 9" rim with 4.5" backspacing. Both will have the same amount of tire/rim on the inboard side.

nclehmann

I agree that both will have the same amount of rim on the inboard side, but the 17x8 wheel will have more tire than the 17x9 wheel on the inboard side. On a 17x8 wheel, a 12.50 width tire will have 2.25" sticking out on both sides. On a 17x9 wheel , a 12.50 width tire will have 1.75" sticking out on both sides. Therefore, the 17x8 wheel is further inboard than the 17x9.

robin

4.5 backspacing is 4.5 no matter how wide the wheel is. while your measurements might be correct. no tire would actually stick out 2.25". tires do shape different depending on the rim width, but not in actual measurement as you're saying it. this is not that difficult to understand, stick to the right backspacing, and it will work.

nclehmann

Actually, the tire would stick out past the rim edge by more than 2.25", since the actual width of a 12.50 tire is more like 13".

I know it's not difficult to understand, and I do understand the difference between backspacing and offset. I guess my thought process is more academic than real-world. I am going to go with a wheel that has 4.5" backspacing, regardless. But I still feel that the 17x8 wheel will have more tire sticking inboard than a 17x9 for the reasons I explained in my previous post. I doubt 1/4' - 1/2" would make a difference, but I thought I would ask to be sure.

JK^2

You're right you would have a little more tire sticking into the inboard side with a narrower rim. But I also see a lot of people running 16x8" Cragar Soft 8s with 5" bs and 12.5" wide tires without any reports of rubbing. If that works you should be good either way with 4.5". I haven't done it so I don't know, hopefully someone actually running a similar setup can help a little more.

JulianK

Does this help? Took me a visual to figure it out!

nclehmann

Yes. I looked at the same diagram as I was asking the question. It only serves to reinforce my point. Thanks.