someone on the q-list  made this up, i thought it may be interesting to you
all who want to see how much different it would be if you ran bigger wheels...

chris
--------------------------------------------------copy------------------------
------------------------

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile
Difference
185/70-14         5.1in  12.1in    24.2in         76.0in        834
0.0%
205/50-16         4.0in  12.0in    24.1in         75.6in        838
-0.5%
205/60-15         4.8in  12.3in    24.7in         77.6in        817
2.0%
205/55-15         4.4in  11.9in    23.9in         75.0in        845
-1.3%