Wheel Torque Calculator (Gearing, Tractive Force and Road Speed)

What this tool does

Gearing multiplies torque: wheel torque is the engine torque times the gearbox ratio times the final-drive ratio, less the losses in the drivetrain — 85–90 % is a commonly assumed efficiency for a manual gearbox. Dividing by the tyre's rolling radius turns it into the force pushing the car along, which is why first gear pulls hardest while a tall gear trades force for speed. Power is the same in every gear; gearing only decides how it is split between force and speed. The real limit on launch is grip: the tyres cannot transmit more than the friction coefficient times the load on the driven wheels, so this tractive force is a ceiling before slip.

Formula

wheel torque = engine torque × gearbox ratio × final drive × η · F = wheel torque ÷ tyre radius · v = 2π n r ÷ (60 × gearbox × final drive)

Variables

Worked example

Limitations

• The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
• Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.