I am looking put 18x10.5 rims all around on my 92 Z28.. I found a set of rims with a 22mm offset.. will this need about a 3/8th" spacer to clear the rear and and 3/4" in the front? Just a little help if anyone been in this situation..

 

For 18x10.5 or 18x11, the back spacing is:
6.0in front6.5in rearSo for a 18x10.5 that'd be +6 front, +19 rear.
For a 18x11 that'd be +0 front and +13 rear.

whatever spacer combo would get you there.
3mm spacer in the rear (about 1/8in)
And 16mm in the front (about 5/8)

I have 3 vids on 18x11 fitment on my channel.
all the cutting, hammering, fender rolling, grinding ex ex is covered.
https://m.youtube.com/watch?v=bjaSPCiYrH0
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We run 6 inch backspace up front on a 2 piece rotor with a 1/2 inch thick rotor hat. Rear started at 6.5 inches but is now at 6 inches. A 315/30/18 had enough sidewall flex in high speed corners to flex in over 1/2 inch at 1.5+gs on track that we reset the hoops on the 3 piece wheels to 6 inches to prevent tire rub in hard cornering at places like Road America and Daytona. Camaro and Firebird have different fitment issues due to ground effect design on each. On our GTA, no cutting was required to clear. Just a few hammer strikes inside the inner rear wheel well. The Camaro required more effort to clear the ground effects on the front.

You will want to fit and measure for best results. Some spacer may be required.