well stock gt is 195/60R15 so the stock diameter for the rim and tire is 24.25 inches. to keep you speedo pretty reliable you want to stay within 2% of this number so + or - 1/2 inch ( approximately, it actually a little less)
so 215/40, 215/45, 225/40, 225/45 are all fine
stay with this and you don't have to get your speedo recalibrated
the closest to stock on 17s is actually 205/45R17
[ 04-23-2003, 08:26 PM: Message edited by: RicePowered ]