hope this is the right section to post in. i figured these questions are more about aftermarket rims than stock, so i went here. anywho...

little confused about the difference between offset and backspacing. I'm trying to find a rim to mount a spare tire on for my xj, but it's been difficult to find a match.

my current rims are 15 x 8 with -30 offset and 3.25 back spacing (according to manufacturer website). i've found a couple different brand new steel rims on ebay for cheap as they had dings or scratches and couldnt be sold as new, but they had 3.75 backspacing. is that wider or narrower? is it bad if i had that on there with mine?

what does the -30 offset mean? haven't seen that mentioned in any other rim listings except for the ones on the website from my rim's manufacturer.

i know i could avoid all this hassle if i could just buy a new one of the same rims i have, but they're a little over a hundred bucks each, and i'm really just trying to find something cheap for now.

thanks,
john

 

I went with Jegs D-Windows at $45 a piece. 3.75" back spacing. They stick out a bit further than stock.

http://www.jegs.com/p/JEGS-Performan...95303/10002/-1

How they look on mine:


Stock:


As my Jeep is stock, the front tires rub a teeny bit when I'm turning while backing up... but only sometimes. I have to have the wheel at a certain angle for it to happen, and I've figured that out so I can avoid it.

Since my rear leafs are so worn and saggy, if I hit a good bump, the rear tires hit the fender flares. My lift kit will cure this problem...

But other than those two minor issues, for the price, I LOVE the look of them and it hasn't affected handling in any negative way that I've noticed. If anything it feels a bit more stable on the road.

 

rim offset : take the 8 inch (width), draw an imaginary line to cut it in half, so 4 inches (middle), then subtract 30mm (offset) and that would make one side 3.25 inches (backspace).

backspace : measurement from rear mounting surface to rear lip of rim. (depth of rear dish). the lower the number, the further the wheel will stick out from the axle.

 

gotcha, thanks! so i should really keep trying to find another rim that's 3.25, rather than having to stick a narrower 3.75 on there? or is it not a big deal, cause it's only for a spare and shouldn't ever be on there for long even if i do have to put it on?

thanks for the help guys.