your spacer needs to be the same as what you widened the wheels, plus the 12mm. if you just add a 12mm spacer you'll be off. the 12mm bringing it to +30 is only for the stock width.

 

the stock wheel, as we know is an 18x7.5 +42, 5.9" back spacing. so if you widen the wheels 1 inch to 8.5" it will then change your backspacing to 6.9" and offset to what we'll call a +55 offset. 1"=25.4mm. 151mm(+42offset on 7.5" wheel)+25.4mm1"=176mm. because the wheel is now 1" wider and 176mm(+55) offset. your wheel will not change position in relation to the fender, however it will be 1" closer to the strut.

so to bring the wheel away from the strut, you'll need a 1" spacer. and with an 8.5" wheel that was widened 1" from a 7.5" wheel. that will put your 8.5" wheel at a +30 offset.

 

Thanks for the advice. I guess I'm just a little confused as to gown widening the wheel changes the offset. I think I just forgot to take back spacing into consideration.

 

Btw where in Oklahoma are you from. I'm originally from Sulphur lol

 

i hate saying my exact location. but i'm about 35-40min north of tulsa.

 

You are thinking correctly but your calculations are mistaken. Widening the wheel 1.5" would add 38mm to the offset bringing it to an overall 80mm offset. Widening it by an inch would bring it to a 67.4mm offset.

To get to a 30 (or 33 as I would recommend with a 9" wheel and a 255 tire) would require a 50-47mm spacer to achieve that final offset. Or a 34-37MM spacer if only widening to 8.5.

I would love to see this done though. The only reason I did my hub swap was to run 255's I loved my stock wheels too.

 

Read the post. He wants 8.5 stock is 7.5, thats an inch.

 

You reread my post. I gave calculations for both.