Effective torque (often referred to as wheel torque or torque to the wheels) is a concept primarily associated with automotive tuning. Torque can be measured using a dynamometer. Common units used in automotive applications can include foot-pounds and Newton·meters.[1]
The formula for effective torque to the wheels is:[2]
Tw = Te * N * η
N = N * N
η = η * η
... where Tw is wheel torque, Te is engine torque, N is the gear ratio, η is the efficiency, and the subscripts t and f are for the gearbox and differential, respectively. Effective torque is often 5-15% lower than the shaft or crank ratings of an engine due to drivetrain losses.