I decided not to use the pair of 19" x 10" rears I have for drag radials b/c 19"s are just too hard to find & too much $ IMO.
So I want to just pick up an extra pair of 18"s, or even 17"s if cheap enough & they fit right.
I will be driving to & from the track on them so nothing that will make the drive (Approximately 100 mi round trip) a PITA.
I was thinking just pick up an extra set of 18" x 8.5" fronts & be done, but maybe I should just go wider. The key here is cheap. I'm not spending a fortune on this b/c I don't track the car on the regular.
I'm running stock 18 x 8 1/2 with MT 265/40/18. They are almost stock size. Checked with GPS, no tune change and my speeo was one mph low vs GPS. You would think high but not according to my GPS. And I had the mph in my tune right on before the tire install using Nitto Invo 285/35/19.
I found a pair of 17" x 8.5" C5 rims. Now to find tires
The lightest and stickest is the Hoosier 17330 - 275/40/17. Like Gary said the 9 1/2 wide would be best but the 8 1/2 should work. Just won't get full contact with too narrow wheel. Which means less traction for a give pressure.