The WIDEST Tire

[NeytVision at aol.com]

What is the widest tire that will fit in the stock wheel wells of the 1991 
200 20V TQ?  The stock tire is (215 60 15 or 639mm diameter).  I believe I saw 
Chris Miller run a (255 40 17 or 635.8mm diameter).  I don’t drive the car too 
far so planned on putting a matched set of Yoko 032R (probably soft compound). 
 What is the best rim width for the larger size tire?  Who makes the 
sturdiest/lightest rims?  Will these wheels also fit a ’92-‘94 S4?
 
TIA
Chet B