i just ordered a one piece BBK from Exclerate...
I have two sets of rims; my stock 17'' and 18''x 7.5 +48 offset.

17'' are my winters of course; so i ordered a 5mm spacer for that...

how thick should the spacers be for my 18''s?

thanks for the input guys (=

 

Really depends on the spoke design of the 18's.

If it's a Rotora BBK you bought, here's a link to a template to check the backspacing on your rim:
http://photos.imageevent.com/allout/...e141-40088.pdf

http://photos.imageevent.com/allout/...struction1.pdf

 

on the 18s you might not need spacers but if you do the 5mm should be enough.

offset has some, but not much, to do with bbk clearance. even more is the distance from the mounting hub to the spokes (backspacing). some bbk sites how a sketch on how to measure clearance for their system.

NM allout beat me and found all the info.

 

thanks for the input guys (=
The rims are on my Avatar if you can see (=

thanks again guys