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12-24 Edition 47
On-Highway Trucks
Appendix A
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Reference Equations (English Units)
Reference Equations (English Units)
MPH =
60 × RPM
M × Ra × Rt
*Miles per Hour
M =
60 × RPM
Ra × Rt × MPH
*Tire Revolutions per Mile
Ra =
60 × RPM
M × Rt × MPH
*Rear Axle Ratio
Rt =
60 × RPM
M × Ra × MPH
*Transmission Gear Ratio (Top Gear)
RPM =
MPH × M × Ra × Rt
60
*Revolutions per Minute (Engine)
Torque =
HP × 5252
RPM
Torque in lbf-ft
Horsepower =
Torque × RPM
5252
Horsepower in lbf-ft per Second
*No Drop Box or Auxiliary Transmission.