Need backspace/offset help

[josh2276]

I recently purchased a 1985 GMC 2500 with a 4" lift on it. My boss gave me 5- 33x12.5x16.5 BFG AT's that have about 1000 high way miles on them. I need to get rims for the tires and dont know what backspace/offset to get. I have two different rims that i like but dont know if they will work or not. I have done a bunch of searches and really cant find what i am looking for. Thanks for all of your help.

1st rim: 16.5x9.75 with 4.375 backspace and -25.00mm offset
2nd rim: 16.5x9.75 with 4.875 backspace and -12.00mm offset

I dont want the tire hanging really far out of the wheel well maybe a couple of inches or so and i dont want to deal with any rubbing issues. I also noticed there is a very big difference in the offset on both rims, what does that change? Thanks again.

[josh2276]

Come on everyone.....nobody has any idea. I need to order rims for these tires i have and any help would be awesome.

[Da67goatman]

I'm running 33 12.5 16.5 on my stock 3/4 ton Suburban with no rubbing.  When I first got them, they were on 9.75in wide steel wheels and they rubbed with every bump and turn.  I used stock steel ford rims that were 6.75in wide to remedy this.  I have no measurements for the backspacing or offset on mine but they cant be much and the tires are right in line with the fender on mine.  I would recommend using 8.25in wide rims for a little more rim protection and to prevent any rubbing.  I can tell you that they only contacted the back side of my fender opening when at half lock and the top lip of the opening at full flex.  I hope this helps.

[Captkaos]

4" came stock with an 8" rim, I would say either should fit but the one with 4.375" would be ~.5" more towards the body.

[josh2276]

I'm running 33 12.5 16.5 on my stock 3/4 ton Suburban with no rubbing.  When I first got them, they were on 9.75in wide steel wheels and they rubbed with every bump and turn.  I used stock steel ford rims that were 6.75in wide to remedy this.  I have no measurements for the backspacing or offset on mine but they cant be much and the tires are right in line with the fender on mine.  I would recommend using 8.25in wide rims for a little more rim protection and to prevent any rubbing.  I can tell you that they only contacted the back side of my fender opening when at half lock and the top lip of the opening at full flex.  I hope this helps.

Thanks everyone, if your suburban is stock with 33x12.5x16.5 and you ran 9.75" wheels and it rubbed then i am not worried with my truck then with the 4" lift.

[josh2276]

4" came stock with an 8" rim, I would say either should fit but the one with 4.375" would be ~.5" more towards the body.

Thanks Capt, when you say .5" towards the body how much do you think those rims will have the tires outside the fenders? Sorry for the dumb questions but this wheel stuff really stumps me. If factory backspace is 4" and those rims are 4.375 is that where you get the extra .5? What does the -25.00mm do to the placement of the rims/tires on the truck?

[bigwillie82]

33" s wont rub if the springs are not sagging, and a true 4" but 35"s plan on your tires eatin right fender.

[josh2276]

33" s wont rub if the springs are not sagging, and a true 4" but 35"s plan on your tires eatin right fender.

Thanks bigwillie82, i am not sure what shape the springs are in as far as sag. The truck has a 4" rough country lift on it.....springs up front and block on the back. I just ordered new shocks for it last week. 

[malibu795]

IMO go with rim choice #2


the NBS rims (00-08 2500hd/3500) run 5.125" backspacing... and no enterfearance.

[choptop]

1st rim: 16.5x9.75 with 4.375 backspace and -25.00mm offset
2nd rim: 16.5x9.75 with 4.875 backspace and -12.00mm offset

i believe this is where he was getting the .5 inch closer to the body. If thats the case and the wheels match, put the 4.375 in front and the 4.875 in the rear since the rear in usually narrower than the front.

[josh2276]

Thanks for all of the help guys. I ended up ordering a set of the first rim on the list. Should be here on tuesday.

[malibu795]

1st rim: 16.5x9.75 with 4.375 backspace and -25.00mm offset
2nd rim: 16.5x9.75 with 4.875 backspace and -12.00mm offset

i believe this is where he was getting the .5 inch closer to the body. If thats the case and the wheels match, put the 4.375 in front and the 4.875 in the rear since the rear in usually narrower than the front.

think you got it backwards
put option#1 ont he front and 2 on the back