tw!sted

Sorry to bump this up again. So offset has no effect on the backspace? Essentially offset is the backspace?

Reason for asking is the wheel lists both offset and backspace.

(eg.

The 17x9 wheel shows Backspacing: 4.7" (121mm) with an Offset: -6mm (-0.2")

Yet on the same wheel in a 16x8 the backspace is listed as Backspacing: 4.5" (114mm) with an Offset: 0mm (0")

^ Why is the offset listed as 0mm on the 16x8 wheel? This is whats confusing and making me think offset somehow comes into play. Its 4.5 BS on the 16 inch wheel and 4.7 BS on the 17 inch wheel, however the 17" version has offset.

Maybe just a typo on the site, but just want to be sure.

nthinuf

Nope, not a typo. Backspace and offset are not the same thing. They are both methods of determining distance from the rims centerline, but their measurements are taken from different parts of the rim.

Here is an old thread from Discount Tire that goes over it.

https://www.jk-forum.com/forums/modi...relate-136663/

As noted back in post #6, Offset uses the actual rim width in the formula when converting it to backspace. In my example from that earlier post, two rims with the same offset, but different widths, gave different backspaces. In your example, even though the backspaces are similar, the offsets are different because the rims are, again, not the same width.

This is why I mentioned that offset is tricky to use, and it is easier to just convert it to backspace -- and then ignore the offset numbers...

(then again, there are a few people on here who have posted that using offset is much better than using backspace. But for me, backspace just makes so much more sense than thinking about a centerline and moving +6 millimeters or -12 millimeters from that point.)

ReadyToMount

They are one in the same. You can calculate Backspacing using the offset of the wheel and vice versa. You need to know the width of the wheel. Offset is variable depending on wheel width. Backspacing can be 4.5 inches on a 7” wide wheel or a 12” wide wheel. The offset in both cases would be different.
Easiest way to picture offset is to imagine looking over the top of the wheel and know that a 0mm offset would put the mounting pad in the center of the wheel. Positive offset moves the pad forward and Negative offset moves it rearward.
If you know the offset is 0mm on a 10” wide wheel then you would know the backspacing is 5”, the little tricky part is you want to add ½” to the backspace number to account for the lip of the wheel.
So the difference is the way you express the number but the end result is the same.

MKPjk08

Im running 37 13.50 x 17 tires on a Walker Evans bead lock rims the offset is 4in andi have an inch and a half spacer and my wheels are 3-3.5 inches out past my stock fenders don't know if this helps but there's my two cents.

null

Doing some research, posting to remind myself.

rcooley

This thread has been helpful, but still raises a question. I want to replace my stock sahara wheels (which i hate), but keep the dueler 255 70R18's for another year or so, because they ride great on the highway, and have plenty of A/T capability at the moment for getting us down to our cabin (which burned down last summer), or for me to go fishing. However, I wish to replace the stock wheels with an 18x9 wheel so that when I do replace the tires I have choices. The stock wheels are 18x7.5 and have 6" of BS with + 45mm offset. The wheels I'm currently looking at are black Procomp series 89 which have a 4.75 BS with -6 Offset. I know the replacement wheels are a half inch wider than is recommended for that tire, but if I'm not airing them down so hopefully it shouldn't be a problem for the short term. I'm more concerned with maintaining the ride characteristics provided by the stock wheel/tire set up. Would the scrub radius (and therefore the ride) change significantly with this replacement wheel? Thanks for any feedback.