quick question?

what's the maximum spacer size that can be used before i would need to put on extended studs?

rule of thumb that I go buy is the lugnut is able to thread on 5 revolutions at the minimum.  Some rims are thicker between the pad and lug nut seating area so you have to take that into consideration too.

so a 20mm spacer generally shouldn't be a problem?

For slip on style spacers? 5mm or less and even sometimes 5mm is too much.

For bolt on spacers you don't need extended studs as the lug holes on the spacers are recessed. However don't run 30+mm spacers...

20mm you will definitely need extended studs. I've never ran spacers before but I personally wouldn't run anything more than a 3mm slip on spacer

20mm would be a safe bet. Make sure you have quality spacers and torque to spec.

[QUOTE=whabbahead9;461988]so a 20mm spacer generally shouldn't be a problem?[/QUOTE]

I hope you dont mean a 20mm slip on spacer on stock studs ...i ran a 7mm slip on spacer with no problems i wouldnt do anything more than that though!

the bolt on spacers require it to be a certain thickness or more and sometimes the wheels don't work since the old threads stick out past the spacer mounting surface.

I've yet to see any car that would [i]safely[/i] take more than a 5mm bolt-on on stock studs. I'm sure there are some that have enough threads to do 7 or 8mm, but better to be on the safe side. If you're looking at 20mm, definitely go to a bolt-on.

From Motorsport Technology, the minimum thickness for a bolt-on is 19mm, but I've seen some on UpGarage as slim as 15mm. But you'll have to cut down your stock studs to run a spacer that isn't thick enough to completely hide them (otherwise the wheel will not seat on the spacer properly).

I'd say from 8-15mm is extended stud territory, generally speaking. Exceptions will happen.

im guessing op is referring to slip on spacers using stock studs right?

Anthing upto 5mm ( some say 3mm ) is ok to be used on stock studs.

Upto 15mm use extended studs

beyong 15mm use the bolt on types.

And always use hubcentric spacer

Also bolt on requires it to be a certain thickness for it to work like mentioned above.. some companies would only use bolt on types from 20mm and up

some do it at 15mm bolt on type.. not sure how i feel about this tho..

only company i know is Akata that made a 10mm bolt on type.. in that case.. the studs just broke off the spacer.. happened to a few guys.. a certain amount of thickness is needed to keep the studs in place.. not sure how much personally but most companies recommend 20 mm thickness.