-12 offset and 4" BS wheels on 91 (1 Viewer)

[mulchiro]

I know I am going to get yelled to search this, but I am a wheel newb and I am having a hard time understanding offset and backspace.

I have a 91 on stock 15x7 rims and I want to upgrade to 16x8 so I can handle some wider tires. (yes I know it's possible to go wider on 15x7, i just don't like the look and I'd rather play it safe) Someone locally is selling a set of procomp 69 series 16x8 with some good shape bfg ko2s attached to them. I've read many different things about the 91 alloys backspace and offset and I really haven't found a straight answer, mostly because I think a lot people with the post 92 16x8 rims assume they're measurements are the same?

the procomp wheels are 4" backspace and -12 offset with a 6 lug 5.5 pattern. I know the lug pattern is correct, just trying to understand if the backspace and offset are as well. Anyone running these on their 91/92?

Thanks in advance. Here is a picture of my rim:

 

[Springs505]

A couple comments: I am pretty sure a 4 inche backspace on an 8 inch wide wheel has 0 offset, so I'm not really sure what you have here. I would try to test fit, if possible. Also, make sure the center bore is large enough and that you use the correct type of lug nuts for the new wheels.

 

[mulchiro]

So this is where I get confused about this stuff. Here is the specs for this rim on the procomp website. It definitely says 4" backspace and -12 offset.

 

[malteserunner]

The width of an 8" wide wheel is measured inside the lip of the bead. Offset is the measurement of the mounting surface in relation to the center of the wheel's width.

Backspace is measured from the wheel's mounting surface to the inner bead's outside edge.

The thickness of the wheel's bead makes the backspace measurement different from the offset measurement, in relation the the center of the wheel.

Example:
An 8" wide wheel, with a 0 offset might have 4.375" backspacing, assuming the thickness of the bead is .375".

An 8" wide wheel with 4" backspacing, would then have a -12 offset, assuming the same bead thickness.

Offset is measured in millimeters, and backspace is measured in inches.

 

[mulchiro]

The width of an 8" wide wheel is measured inside the lip of the bead. Offset is the measurement of the mounting surface in relation to the center of the wheel's width.

Backspace is measured from the wheel's mounting surface to the inner bead's outside edge.

The thickness of the wheel's bead makes the backspace measurement different from the offset measurement, in relation the the center of the wheel.

Example:
An 8" wide wheel, with a 0 offset might have 4.375" backspacing, assuming the thickness of the bead is .375".

An 8" wide wheel with 4" backspacing, would then have a -12 offset, assuming the same bead thickness.

Offset is measured in millimeters, and backspace is measured in inches.

Ok that makes sense to me. What I am having trouble understanding is how these measurements relate to my current stock rims and if they will actually fit. I have read differing statements on threads both here and other places stating the backspace and offset of the 15x7 rims.

I really am just hoping someone can tell me if they will fit my 91

 

[malteserunner]

What tire size are you going with, and what about suspension? Lifted?

 

[malteserunner]

Assuming you have approximately 4.25" backspacing on your stock wheel, you will gain 1/4" of clearance on this inside bead, and push the outer bead 1 1/4" further out from stock.

 

[mulchiro]

What tire size are you going with, and what about suspension? Lifted?

Was planning on 285/75/16. I have a 2.5" OME kit in the mail.

 

[malteserunner]

You should have no fitment issues with that setup.

 

[mulchiro]

You should have no fitment issues with that setup.

This is exactly what I wanted to hear. Thank you sir!

 

[malteserunner]

You're welcome. Post some pics when you get it done!