Back spacing

[SCOTI]

Originally Posted by ibinyth

Looking to possibly run rocket racing attack titanium wheels. It's a 70 c10 4/6 drop wheels will be 18"

Not sure if I can run a 10" up front or not, front is stock arms, here are the options for back spacing... I do own a angle grinder if need be

Front
18x10 5", 5.5"
18x9 4.5", 5"
Rear (no tubs or bed floor) I believe I have the later rear end, I remember my axle shafts were 31.313", I don't have the rear end with me, it's being rebuilt.
18x12 6", 5.5"

I answered in the Suspension forum but I'll add a little more here....

Typical trucks w/a 4/6 drop & factory 6-lug pattern can run 4x4 15" truck Ralley wheels in back w/o issue. They have 4" back-spacing. There might be a little wiggle room going out-board but not much.

Using that as a starting point helps do the math quickly....

8" wheel w/4" back spacing fits no-problem.
9" wheel would need 5"BS to fit no problem.
10" = 6"BS
11" = 7"BS
12" = 8"BS

Given those numbers for a 'no-problem' fit to the outside sheet metal, you can WAG how much wiggle room you have before it requires a different number/combo to work (ex: 12" wide w/6"BS is going to stick way outside the body & will require narrowing the rear end or flaring the wheel opening; 12" wide w/7-7.5"BS might work but would be close).