Big Tires


 Diameter Radius Circumference
 30" 15" 30p = 94.24777961"
 31" 15 1/2 " 31p = 97.38937226"

The circumference represents how many inches the tire will travel for ONE revolution.

Therefore the circumference (in inches) must be converted to miles.

 

94.24777961" * 1 '/12" * 1 mile / 5280 ' = .0014874965 of a mile

 

97.38937226" * 1 '/12" * 1 mile / 5280 ' = .001537097 of a mile

 

Now we consider the rate 55 mph calibrated for the 30" tire. D = R*T

55mph/ .0014874965 of a mile = 36974.87638

36974.87638*.001537097 = 56.83397156

So if you enhance your tire to a 31" diameter your speedometer should read approximately 57 mph.


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