Originally Posted by BIZL
I think I could get away with running a 5/16th spacer which would keep the wheel pretty close to flush with the fender.
That brings me to another question. How thick of a spacer can i use before I have to installer longer wheel studs?
You need as much clearance as will allow you not to rub, it'll be different for different cases. It will also depend on your suspension, as stock type springs get wider at the top, so you might be getting reduced clearances under compression. Pick a spacer that you think will work and try it out, if it doesn't rub then that's great, if it does, go thicker. It's not like spacers are expensive.
There is no hard and fast rule about spacers, because every wheel is different (some have thick hub faces), and anyone who tells you some arbitrary number is an idiot. Some wheels don't even get a safe amount of thread engagement without spacers, so longer studs are required right off the bat and any spacer will be unsafe on stock studs.