I searched for an hour and couldn't find a definite answer as to what size wheel and tire I need. This is for my 2002 A6 4.2 so it has the flared fenders. It has the sport suspension so it sits a hair lower than others. I'm looking for a Wheel and Tire combination that will fill out the arches a bit more than the stock 17"s do. Theres just too much space between tire and fender. I do not want to lower it any more, at least not yet. I prefer to go with an 18" or 19" wheel with decent rubber for crappy northern roads.
I do like the RS6 style wheels but I know there are many others. I really need to know:
Wheel Size
Tire Size
Offset
If spacers are needed what thickness?

I live in a place where tire shops know virtually nada about aftermarket parts... Sure appreciate any answers...

 

18x8.5/+25mm wheels with 255/35's should help fill that gap.

 

Thanks for the input, Much appreciated
I understand the 18x8.5 easy enough but does the +25 offset just push the wheel out towards the fender a bit more than say a +32 offset? This would eliminate the need for a spacer?
Or does the +25 offset suck the wheel in towards the car?
I assume going with a bit taller tire would interfere with speedometer readings,axle ratio,and possibility of rubbing? So sticking with the 35 sidewall measurement is a must?

 

Yes, +25 mm offset will push the wheel further towards the wheel flare lip than +32 mm. Offset is the distance from the wheel hub surface to the centerline of the wheel. Backspace is the distance from the wheel edge (lip included) to the wheel hub surface. Therefore, the lower the positive offset, the less backspace you have.

For a 255 mm wide tire, yes, you should stick with a 35% sidewall aspect ratio. This will get you (theoretically) pretty darn close to the OEM tire overall diameter (~25" dia). If you go with, say, a 255/40-18 the overall diameter will be 26" and at a speedometer-indicated 70 mph, you are actually doing closer to 73 mph.

Hope this helps!