Though the terms 'tyre' and 'wheel' are often used interchangeably, the wheel is the tyre and rim assembly. Wheels are installed on vehicles at the hub, which is a mounting surface that allows wheels to rotate.

Related Pages

Browse Wheel Prices
Pros & Cons of Alloy vs Steel Wheels
Wheel Balancing
Tyre Maintenance
Car Maintenance

Before installation, wheels must be individually tested for balance. The balance test tells the technician whether or not a wheel has an even distribution of weight. Imbalance is corrected by adding weights to the rim. Machines are used to balance wheels. The test involves two phases, testing balance when the wheel is stationary (static balance) and when it is rotating (dynamic balance). Different designs and procedures exist for these machines, so the test performer must read a specific machine's instructions on how to operate it.

The technician enters three measurements into the machine: rim width, diameter and distance from the machine. The machine spins the wheel and outputs how many weights should be placed on the rim and where to balance the wheel. After weights are added, the test is performed again. If additional weights are required, they are then added. A final test is conducted, and if balance has still not been attained, the wheel rim is likely to be damaged or even bent. If this is the case the wheel rim will need to be repaired or in the worse case replaced.

Once wheels are balanced, they may then be installed onto the vehicle. The rim contains holes that match up with the studs on the wheel hub. Usually, a technician lifts the wheel up to the hub and slides it into place. Wheel nuts are used to secure the wheel on to the wheel studs. These are installed finger tight at first, then tightened with a torque wrench to specification. This specification can be found in the service manual of the vehicle. When torquing wheel nuts, a star-shaped pattern should be followed to make sure the rim has been located correctly onto the wheel studs. This involves going from the top left nut to the bottom right, then top right to bottom left. If six nuts are used, proceed to the far left nut then the far right last.

Once wheels are mounted in place, it is advisable to check the vehicle's alignment. The purpose of a wheel alignment is to make sure the vehicle will go straight rather than pulling to one side. There are two common types of alignments performed: thrust angle and four-wheel alignments. Thrust angle alignments adjust the two front wheels in relation to the two back wheels; if the rear wheels are slightly out of line, the front wheels will be tilted to mirror the same slant. This is done on rear-wheel-drive vehicles because their rear wheels cannot be adjusted.

Four wheel alignments are performed on all four wheel’s of the vehicle. All four wheels are made to follow a true vertical line. This not only aligns them with one another, but ensures that the vehicle is going straight when the steering wheel is in its straight up-and-down (unturned) position.

Alignments are performed on wheel alignment machines by professional technicians. The vehicle is driven onto the machine and alignment heads are attached to each wheel. The machine takes measurements of the wheels positions and walks technicians through the adjustments that must carried out.