For what it's worth they switched us from 18" Goodyears to the 16" Hoosiers with our wing car last year. I had the same concerns and was pissed I had to buy wheels. I went to FL last year with 3 18" wheels a 17" and an 16". I tryed both the 18" and 17" and never even had to try the 16". We use the 18" 90% of the times, it just didn't seem to much difference. Also they measured up about the same. A 109" chalk mark came up at 106" with the old 18" wide Sc12 and now a 109" chalk mark with the new 16" tire is still 106". I guess what trying to say is don't go buy a bunch of wheels or get discouraged till you run a few races.