Technical Dictionary

Under-inflation

Operating a tyre without sufficient air pressure to support the weight of the vehicle with occupants and additional load; could cause failure of the tyre when heat is generated inside the tyre to the point of degeneration of components.

Under-steer

The handling characteristic in which the front tires break loose because they are running a larger slip angle than the rear tires. Also known as plowing.

UTQGS

Also known as Uniform Tyre Quality Grading Standards. A government-sponsored tyre information system that provides consumers with ratings (from AA to C) for a tyre’s traction and temperature. Treadwear is normally rated from 60 to 700.

Ultra-Low Profile Technology

Specialized sidewall shape, bead area, and bead compound that enhance the durability and mountability of tyres with very short sidewalls.

Undertread

Material between the bottom of the tread rubber and the top layer of steel belts; acts as a cushion that enhances comfort.

Unsprung Weight

The weight of the parts of a vehicle not supported by its springs, including wheels and tires, outboard brake assemblies, the rear axle assembly, suspension members, springs, shock absorbers and anti-roll bars.