Reduction Gear
A reduction gear is a fixed gear arrangement that converts high motor speed into lower output speed and greater wheel torque.
What it means in an EV
Most passenger EVs described as “single-speed” still use one or more gear meshes. “Single-speed” means there is one fixed selectable ratio, not that the drive has no gearbox. The reduction ratio approximately multiplies motor torque at the output after mechanical losses, while output speed falls by the same ratio. It does not create power.
Engineers select the ratio together with motor speed, torque, efficiency, tyre size, gradeability, acceleration, and top-speed requirements. A numerically larger reduction increases wheel torque for a given motor torque but also makes the motor spin faster at a given road speed.
For gear layouts, ratio selection, multi-speed exceptions, lubrication, and loss mechanisms, see EV Reduction Gears and Transmissions.