[tryan]

one less calculation if you could give the tire width and rim size.

126 miles /hour x ( 5280 feet /mile ) x ( hour/3600 seconds ) = 184.8 feet/second

i fill assume a 205/60 15 which would give a rolling radius of

205 X (60%) =123 ( divide by 25.4 to meteric ) 4.8425"

plus rim radius 7.5" + 4.8425" = 12.3425" rolling radius (1.0285')


now the rpm of the tire.
perimeter 2 pi r...... 2 x ( 3.1416 ) x 1.0285'= 6.4625' /rev

velocity/perimeter= rev/time

(184.8 feet/sec) / (6.4625'/rev) about 28.59 rev/second


with the new aspect ratio for a 50 series.

205/50/ 15 rolling radius is 102.5 /25.4 = 4.0354 + 7.5 =11.535" radius
rolling diameter 11.535 x 2 x pi = 72.476"/rev


assume 28.59 revolutions /sec x 72.476"/rev = 2072"/second

117.73 mph if you have 205 /50 15's

probably some bad math somewhere. plug in your tire size




i'm loosing it. 3 posts before i could figure it out