Eric, I can imagine that you only used 2-3-4 in your 5 speed box with both the 14" and the 15" tire?

I know that when I ran my GTI in ITB, running the Toyo 205-55-14 I NEVER used 5th gear, but since I converted to GP, and run the 20x8x13 slick, I only use 3-4-5 at the same tracks.

This is with a stock close ratio 020 box, with a 3.94 R&P.

Bottom line, if you change your R&P to a 4.50 or 4.83, go with a "taller" tire, other wise, it depends on the track and the overall diameter of the tire/wheel package.