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Calculate MPH, RPM and more...
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By Scott H.
- J&P Cycles Tech
| Learn how to calculate MPH, RPM, Final Gear Ratio, and effective rear wheel radius. |
The following four formulas are used to calculate MPH, RPM, Final Gear Ratio and Effective Rear Wheel Radius.
When we have any three of these we can compute the fourth using a constant (168).
Lets define a couple things here:
Effective Rear Wheel Radius (ERWR) is measured from the axle center to the ground, with the desired tire pressure and the rider seated with feet on the pegs. Tire pressure can have a
dramatic effect here.
Gear Ratio is Total Ratio, or primary x secondary.
The formulas:
MPH = (RPM x ERWR)/(GR x 168)
RPM = (MPH x GR x 168)/ERWR
GR = (RPM x ERWR)/(MPH x 168)
ERWR = (MPH x GR x 168)/RPM
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