Brake rotors are disks which are mounted to the wheel hub, inside the rim of the wheel. They provide a surface for a brake pad to clamp on to, creating the friction necessary to slow down a vehicle. Some are built into the wheel hub, which forces one to replace the whole wheel bearing assembly if a rotor gets too warped, but most slide on the wheel studs of the hub the same way a wheel does.
Drilled & Vented Brake Disks
Normal metal brake discs can be improved upon with professionally-drilled brake vents. Some sports cars come with drilled brake vents, and many aftermarket manufacturers produce replacement brakes that are drilled/slotted.
Upon first glance, some people may think these brakes reduce surface area used to create friction, and are only there for aesthetic appeal. This is partially correct, since it does reduce surface area that comes in contact with the brake pad, but the gains from the lower temperatures more than make up for the small loss of friction.
Holes drilled straight into rotors create sharp edges that can speed up brake pad wear, but some manufacturers round out the edge to alleviate this. Vent grooves tend to be easier to put in without sharp edges, but since they are only pockets of air and not a way for air to escape entirely (through the hollow rotor core), they tend to not cool the brakes as well as their drilled counterparts.
Rotors are meant to be a uniform friction surface for brake pads to contact, but sometimes harsh conditions can cause a heated rotor to bend slightly out of shape, which can cause reduced braking performance and a shuddering brake pedal when in use.
Causes of Warped Rotors
There are many causes of warped rotors, but the most often overlooked and easiest to avoid is properly torqued set of lug nuts. Tightening the lug nuts in the correct pattern, to the correct torque, and without using any damaged or mismatched1 lug nuts is the most important step to take to prevent rotor warpage in a typical daily-driven vehicle.
- Brake Pads
- Wheel Bearing
- Wheel Hubs
- Nuts & Bolts
Articles Related to Brake Rotors
1 Some sets of lug nut locks come with one lock per wheel and the rest are normal, and these are acceptable because they have been designed as a set and have the same amount of friction area.