Am thinking of fitting Stoptech brakes ? Need to know what offset is required when fitting 18" replacement rims - same size F & R. Also, how wide can 18" rims be without having to roll mudguards ? Thanks.
It would depend on which of Stoptech's range you're looking at buying. I would suggest speaking to the company you're buying from as they'll be able to either give you measurements or a template, or possibly a straight offset to reference. However often the offset is only part of the equation, the spoke design plays a BIG part in defining if it clears your calipers or not. Ie you could have a relatively smaller offset, but perfect curve on your wheel spokes and clear, rather than needing a potentially larger offset to 'be sure'.. Who are you looking at buying from? When I bough my BBK from Concept Z they were able to provide a physical template that I could print out and sit inside my wheels to check clearance. Worked perfectly.
Like Andrew said fitment for brakes depends more on the spoke design. No guarantees but generally you need a low offset with concave spokes. Fitment for the guards depend on ride height, offset and width. Rears will fit bigger wheels. Since you want a set of the same wheels front and rear then 18 x 9 +30 is about the limit and already a bit wide for the front if the car is low. Stock height it fits ok front and back.
When you look at the style you want you can get the spec's eg high, medium low disc... its for brake calliper clearance. On my 300 I had 18 x10 +22 fit... But after went to staggered 18x10 +15 f and 10.5+22 r(once I lowered it heaps in the rear needed to roll the rear lip). You can check a website called rim tuck to find wheel specs and pictures or use a offset calculator to work out rim clearance.
As suggested above the StopTech website will have templates you can print out to check wheel clearance.
