Brake Discs and Calipers
Brake discs
The disc (or rotor) is a heavy plate attached to the wheel hub, so providing a two-sided braking surface.
As brake systems develop, manufacturers seek better metallurgical combinations for discs to achieve better brake performance. This often means a softer metal compound which can result in discs that have to be replaced more often. A disc has a typical wear life of around 2 to 4 millimeters, so make sure that it is checked properly and replaced when worn.
The most common cause of damage to disc brakes is when the friction pads are not replaced in time, damaging the disc surface when metal touches metal.
Disc skimming renews the friction surface, and discs should ideally be machined on the car, as it is then set up perfectly true to its natural plane of rotation. Pedal flutter is felt as a gentle oscillation on the pedal, but can shake the front suspension violently under braking conditions. To read more about pedal flutter and stacked tolerances, look it up on the POWERBRAKE page.
On some models it is cheaper to replace the discs than to skim them. This will only temporarily solve pedal flutter - if the new discs are not skimmed, pedal flutter will return after a few thousand kilometers.
Brake calipers
The caliper straddles the disc like a clamp, and when pressure is exerted via the brake fluid onto the caliper piston(s), it pinches the disc between the disc pads and slows the wheel (and your car) down.
Brake calipers require new seals in their pistons from time to time, and sometimes pistons tend to rust solidly in their bores. Torn dust covers will allow ingress of dirt and moisture, contributing to seizing tendencies. Seized pistons are best dealt with by brake experts that have the correct hydraulic equipment to dislodge them without damage. Calipers are of varying designs, and floating calipers need to move freely on their guide pins. Regular maintenance by a knowledgeable expert is not expensive and can save you money in the long run.
BEWARE!
Where disc brakes are fitted to the rear wheels of a vehicle, the action of the handbrake has to be incorporated in the action of the pistons, and with it one of a few designs of self-adjusting systems. Changing the rear disc pads on such a vehicle is not a DIY job!
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