I'm wondering being an R170 they still went for an advance on the original 16" rims = 632mm overall tire diameter?
albeit on AMG 17" x 7.5/8.5" rims
so
Front 225/45 (634mm), Rear - 255/40 (636mm)

if so and I was looking at 18" rims - that'd mean
Front - 225/40 (637mm), Rear - 255/35 (636mm)

And what are the stock AMG 17" offsets?
---------------------------------------------------------

Another question re the SRT-6's - they seem to run stock 18's? or 19's?...wondering if they have a bigger running diameter and what effect that would have on the perfomance of the car?

I'm guessing AMG have tried to tune everything (particulalry suspension).
The fact that Chysler then went and put 18" and I suspect bigger wheel arches to suit is a conscious decision I guess - better or worse?
Trend lately is bigger rolling diameter but that may be a fashion rather than theoretical thing.

 

stock offset on original 17" 32 wheels:
37 offset front 7.5" w
34 offset rear 8.5" w

I am running 18" SL55 wheels with 30 front 8.5" w & 33 rear 9.5w
Front rims have ~ 1/8" protrusion from wheelwell, without lowering clearance is fine

 

what tires you putting on 8.5/9.5 rims?
I'm hoping more than 225-40/255-35?

 

fronts 235/40. concern was wheel well protrusion so went conservative but will go 245/40 later which is .2" less diameter than stock.

rear is 255/35. also had concern on inner clearances with the new wheels, replacements will be 285/30 which is .1" larger diameter than stock.

I was willing to go conservative with the first set of tires with the understanding I would increase the sizing when the tires wear out. Finding definitive sizing and clearance info for the 32 is near impossible. Just a bunch of "this is what I have & it works".

 

wow 255's on a 241mm rim...that's tight. Doesnt look odd or pulled in?
I'd be interested to see 265's on there - what offset?

---------------
Off yopic - I've notived some of the concept artwork for muscle cars going back the way of the 70's and tapering the toop edge in to the tread.
Miight be in line with the new wave. eg:
http://www.okedab.com/2011-ford-mad-max-interceptor

 

255 in a Hankook v12 is spec'd from 8.5 to 10" (9" optimum) rim so well within spec
285 is at the opposite limit at max width for that that rim

offset 30 front 8.5" w & 33 rear 9.5w

 

9.5 wide 33 et with a 285 will never work. you will kill the inner fender. 265 is all your going to get