A space-saver spare wheel and tire assembly meant only for emergency use to get a vehicle to a repair shop. They are significantly narrower and smaller in diameter than standard wheels, requiring drivers to stay under 50 miles per hour and limit distance to prevent drivetrain damage.
Put the donut spare on the rear and keep it under 50 on your way to the tire shop.
Never put a donut spare on the drive axle of a vehicle with a limited-slip differential, as the mismatched diameter will quickly burn out the differential clutches.
Also heard as
- space-saver spare
- donut
Related terms
Run-flat
A tire designed with reinforced sidewalls to continue operating safely for a limited distance after losing air pressure.
Alloy wheel
A vehicle wheel cast or forged from a mixture of aluminum or magnesium.
Mag wheel
An aftermarket or high-performance vehicle wheel originally cast from a magnesium alloy.