Now that the B8 platform has moved to a 66.5mm centerbore, wheels that fit certain Mercedes Benz cars will also fit our cars, including later model C-Class, E-Class, some CL-Class, and others. Thus, if you're looking at used wheels, or new wheels specified for M-B, you may be able to use them on your S5 or A5. Could be pretty handy, as there would otherwise be fewer options if you were just looking for Audi wheels. The relevant specs are:

Centerbore: 66.5mm
Pitch Circle Diameter (PCD): 5x112 (this is the bolt pattern)
Offset: ET32
Stock S5 wheel width: 8.5"

The thread pitch of 1.5mm is the same, but note that certain wheels use conical seats for the wheel bolts, whereas Audi uses ball seats stock. Depending upon the wheels, you may need new bolts (1.5 R13 is the designation of the stock bolts). Remember, you need at least 7 full turns of the bolt.

Be sure the offset and wheel widths will work for your application. Offset measures how far the wheel's mounting face deviates from the wheel's centerline, and there's an inverse relationship from what you might think. Less than 32 brings the edge of the rim OUT and toward the fender; too little offset and you could get rubbing. Greater than 32 brings the wheel's face IN and closer to the hub; too much offset and the spokes could impact the brakes. Note that this can be managed with the addition of spacers, but it's still important to note the implication of offsets.

Why post this now? I picked up this winter set of 18" wheels *with* TPMS from a guy with an E55. Ironically, even though the guy had them on his Mercedes, they're RS4 reps:

<img src="http://pictureposter.audiworld.com/43649/img_1351.jpg">

The 18" wheels do clear the S5's front brakes easily.

I'll post pics of these on the car when I mount them all up (c'mon, snow).