Just like the topic says, what is the Ideal tire width for 8.5" and 9.5" wide rims?

 

Also for stock c5 y2k rims, 17in rims are 8.5 stock and 18's are 9.5 right? I had a guy say that front was 9.5 and rear was 10.5 and I'm skeptical..

 

I would say 265 for the 8.5
and 275 for the 9.5

 

I'd say...
255-265 for a 8.5
275 for a 9.5
295 for 10.5 (although I fit 315 GS-D3's on this size wheel no problem, and those are really like 325's)

 

C5 Y2K rims are 17x8.5 and 18x9.5 with a 245-40-17 up front, and a 275-35-18 in the rear. which is the IDEAL tire size for those widths.

18"x:

8.5" wide : 235 - 255, 245 being perfect
9.5" wide: 265 - 285, 275 being perfect
10.5" wide: 285 - 315, either 295 or 305 are perfect

19x:

10.5" wide: 285-305
The larger sidewalls will give you more flexibility. ive seen 315s on a 8.5" rim but it was a 315-60-15.