Same reason why I went with 18 over 17 - Much better tire selection. Hope to get my own Saleens soon! (and awaiting that tracking!)Ray, this issue is that I dont have a cast available to me to support those specs. Have you compared prices with a 245-50-17 vs 245-45-18? I think you might be surprised. Availability is sooo much better in the 18's than it is the 17's. This is one of the reasons 17's are no longer as desirable as 18's.