Backspacing/offset question

[Jr]

Hi guys,
I'm trying to figure out the correct backspacing and offset for my new set of rims. Currently the truck has 235/75/15 on a 15 x 7" rim with -6 offset and 3.75" of backspacing. What I would like to put on my truck is 275/40/20 on all four corners. Given the offset/backspacing that I currently have, what offset/ backspacing would I need to fit a 20x10 or 20x8.5 with a 275/40/20?

[Vince@Meanstreets]

depends on how much room left inside and outside. if you can go out more your backspace will be the same....offset will change due to rim width change.

[Jr]

Yeah, I was hoping someone with one of these 67-72 chevy trucks had already gone through this process. I will take my truck down to my buddy for proper figment.

Edit: in my original post, I forgot to mention this is for my chevy truck...stupidity hurts.

[Vince@Meanstreets]

keep in mind that the 20" will have less tire bulge and tire flex than the 15"....so that can free up more room for you.

[DriverzInc]

What wheels are you ordering?

We have a recommended offset for 67-72's that you could double check if will work for you. If the truck is stock height, then you can easily run a 10" wheel on all four corners, if its bagged, or dumped, then we normally run a 8.5 front and a 10 on the back.

[Jr]

I'm looking at the Us mags (mht wheel) five spoke. Yes, the truck is bagged.