question regarding rims
 

Alright after doing some searching i'm a tad bit confused. I'm looking at some procomp 15 inch rims that have 3.75 back spacing. I'm going to run 31x10.50x15 and i'm wondering if i will have an issue with rubbing. i test fit these tires last night and they fit great with my t bars cranked some and didnt rub unless i'm cutting the wheel hard in reverse. Any idea on how wide these tires will be with these rims as far as them sticking out of my fenders.

Thanks

Nick

I believe that they will be 2.25in. past your stock wheels.

here is a better question... I'm looking to stay at 15 inch rims but i dont know whether to go to 15x7 or 15x8. If i go to 8 with my 31x10.50 will it make my tire some what smaller because the rim is wider? Next question... what kinda back spacing would cause less trimming? I put these tires on the rims they came with (nasty rusty things) and the back spacing on these rims are 3.75 and only rub on the plastic trim for the bumper and the little corner on the fender. I'm wondering if 4 inch back spacing would fix this issue. only the side lug of the tire hits. Weird thing is its only on the passenger side so i'm thinking my torsion bars are not even. Also the off set- what exactly does the off set do?

7" vs 8" is really up to you. The tread width on most 31x10.5 tires is about 8-8.5" so 8" wheels would match up well. ZR2's and tons of us have them on 7" wide wheels and I know there are a lot of people that run them on 15x10s. They seem to work just fine on any width

The more backspacing, the better. Stock 4x4 wheels have 6" backspacing (51-52mm offset, see below). 4" will be better than what you have now but even higher will help. I have 4" backspacing and had rubbing in the exact same spots you mentioned. I cranked the tbars and started cutting until the tires didn't rub any more. There aren't a lot of high-backspacing aftermarket wheels so you may have a tough time finding anything with more than 4.5" or so. Also, keep in mind that 4" of backspacing on a 7" wheel will fit differently than 4" on an 8" wheel. This is where offset comes in.

Offset is just another way to measure the wheels and is helpful in comparing how a wheel would fit in relation to the truck even if they're different widths. Say you have a 15x7 wheel with 3.75" backspacing which is equal to a -6mm offset. If you bump up to a 15x8, and choose to get more backspacing like 4", then you're adding an inch to the overall width but only moving them closer to the truck by 1/4 inch. 15x8 with 4" is -12mm offset and might actually cause more rubbing issues. I would recommend at least 0mm or 12mm offset

Here's a good chart that shows the relationship of wheel width (down the left side), backspacing (across the top) and all the numbers in the middle are offset (measured in mm, 1" = 25.4mm)

https://www.rsracing.com/images/tech-wheeloffset.gif

I hope I answered your questions and explained it well enough. :)

that is exactly what i needed. thank you very much i will post pictures once rims are in

ok so then what if i was to use a 15x8 rim with a 33x9.5 tire? what back spacing would i need ?

ok, i need to find some rims quick since i have a drive over the mountain here for christmas to see some family. i paid americas tire co $660 for some decent cooper snow tires 235/75/15 and some unique 297 steel wheels. the steel wheels were taking forever to arrive so they decided to upgrade me to better wheels. they gave me some MB razors instead for no additional cost. i was really excited since these are actually good wheels, aluminum instead of steel, look better etc etc. however after i got home i took a good look and noticed they are sticking out too far imo. i have 2 lines of tread sticking out passed the front bottom of the rocker panel, and 1 line of tread sticking out passed the factory non-zr2 fender. the rear wheel sits flush with the quarter panel, maybe barely a little out, but the back looks great, the front doesnt look right. im worried about throwing gravel and junk up the side of the truck as i drive over snowy mountain passes or go offroading. i need to find a solution to this as fast as possible. either mud flaps (meh) zr2 flares (expensive, even the replicas) and different wheels. the problem with finding wheels is i cant find any freaking offset or backspacing on any retailers website.. is there a catalogue i can look at somewhere that gives me good specifications on wheels so i can pick a set and get them ordered and installed? any help would be greatly appreciated. if there is a set of mb razors with a higher offset that would be great, the ones i have now are -6mm and the factory specs call for like +50??? my wheels stick out like 2.25 inches from the fender