A wheelspin occurs when the force delivered to the tyre tread exceeds that of available tread-to-surface friction and one or more tyres lose traction.
Standard differentials (also referred to as "open" differentials) always apply equal torque to each wheel. In low traction situations, the total torque delivered to each wheel is limited to the torque that is required to make the wheel with the least traction slip.
During a turn, the weight of the vehicle shifts away from the inner radius and to the outer radius, therefore the inner drive-wheel will often lose traction on hard cornering, and especially when accelerating through a curve. Locking differentials and limited slip differentials modify the manner in which torque is distributed to the wheels to reduce wheelspin and improve traction in situations where it is limited.
Wheels can also lose traction when surface conditions reduce available traction such as on snow and ice. As an open differential delivers only enough torque to cause the "weakest" wheel to spin, if one drive wheel is stationary on a low traction surface (mud, ice, etc.), the deliverable torque is limited to the traction available in mud.
Wheelspin can also occur when changing gears while the vehicle is in motion, as the inertia of the engine and flywheel rotating at a higher rate than the next highest gear tries to bring the input shaft of the transmission to the same speed.
In railway engineering, the term wheelslip is used as a synonym for wheelspin.
See also