Thanks Don, the F0 and F1 were still 18" wires. When they went to Comstars on the F2 they went to a 17" rear.
There's a guy in Canada with a set of Shelby Dowd wheels for sale. I know the stock rotor doesn't work with the SD wheel, but it's an 2.15-18, which seemed thin.
I took a look at the wheel on my bike when I got to the shop tonight and it does say 2.15, it sure looks wider though.