I needed a tire effective diameter for a competitive performance 

  analysis program. Doing a 'curve fit' of Firestone Tire data and checked

  against Bridgestone tables, I got a pretty good set of numbers. The

  real speed data shows the output to be representative of a half worn 

  tire (not new).

  

      TireHt = Width * Profile / 2540

      RPmi = 10084 / (WheelSize / 2 + TireHt - .37)



  The attached file "RpMi.gif" is a plot of tire revs/mile vs. profile % 

  as the 70 in P205/70-15 for 14 to 17 inch wheels with lines of const.

  width (as in  205 mm).



  Having checked out your ftp system (Bruce DP told me to look up madkatz),

  I know it works and is great. Thanks for your efforts. I will submit

  plots of Kostov Current  and  kW  vs. RPM if this works.