• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Wheel Offset & Raising the XJ

RAVC1

NAXJA Forum User
Location
Michigan
I'm looking for a calculator that can tell me how wheel offset or, backspacing, varies as we increase tire diameter. Can anyone refer me to a website with online calculators or better yet paper references. If anyone that reads this post knows the relationships answer away!

I'm trying to select my new wheels & tires and need to make sure I retain (or remain close to) the OEM relationship between wheel offset and tire size to keep the loads on the unit bearings and ball joints similar to those observed in the OEM configuration.

The line drawn through the ball joint centers extends away from the vehicle as you raise the vehicle. In order to counteract the outward movement of this line I think the BS/offset should become smaller or, less positive, as you raise an XJ if you want to retain the OEM suspension geometry. Is this relationship linear?

Most of the wheel offsets for the XJ wheels I've surveyed appear to emphasize bad suspension geometry. With the 215/75R15 tire and 15x7 wheel we use 5.25" Backspacing/31.75 mm offset.

The open space under the front wheel house is inward toward the coil spring. However, in the rear my 235/75R15 gives ~1" of space between the inner sidewall of the tire and the leaf spring pack.

Please advise.

Thanks,

Rick
 
Last edited:
jbmoose,

Thanks. I'm not sure how good these are but this is really only part of the issue. What I'm really trying to do is define the geometry of the triangle formed by the following quantities:

1) the sloped line through the center of the ball joints,

2) the vertical component of Line #1 located at the center of the tire tread.
2a) Line #1 & Line #2 should intersect at the center of the tread in the contact patch.

3) the horizontal component of Line #2 - through the axle center - joining Lines #1 & 2.

You need to determine the angle between Line #1 & Line #2 in order to do anything as these three lines form a right triangle. I was Googling suspension geometry.

I thought this would be easier than this. So I'll just have to take the direct measurements from the front axle.

Thanks,

Rick
 
Back
Top