Brake discs for your car

Quality of brake discs equals safe driving

In addition to the brake linings, brake discs are the most important safety components of a car. Much more important than a car's ability to drive is its ability to brake adequately. A high-quality brake disc is inexpensive and considerably contributes to the vehicle's safety.

Simple construction

A brake disc is a cast-metal component, in essence a circular disc of steel. It has a recess in the centre to enable its fixing on the hub. Brake discs are standardly fixed with four bolts. High-performance brake discs have five drilling holes. The brake discs with three drilling holes, once common in French cars, are nowadays hardly used. A brake disc is a one-piece part although different constructions exist. In addition to the simple brake disc for compact cars or cars with reduced engine power, high-performance dual discs with internal ventilation are available. Between the internal and external disc they are equipped with air scoops, permanently supplying air during driving, cooling the disc and effectively preventing overheating when braking at high speed. Internally ventilated brake discs are considerably more expensive than standard brake discs without ventilation.

Constant wear

Brake discs are built as a wear component and this is no manufacturer's trick to earn money, but rather a necessity for the sake of safety. Brake discs absorb the friction forces occurring by pressure of the brake linings against the disc, causing it to glow. An excessively hard and durable brake disc would only lead to brake linings quickly grinding down. The replacement ratio of brake discs and brake linings is 2:1, signifying brake disc replacement at every second replacement of the brake linings. Brake disc manufacturers dictate a minimum thickness. Nevertheless the residual thickness of the brake disc is not the only important criterion for replacement.

Checking the brake disc

Every time the brake linings are replaced, the brake discs must be checked thoroughly. Important are the following points:

• Colour
• Cracks
• Grooves
• Residual thickness

Excessive glowing causes a bluish hue on steel. The steel hardens and loses its flexibility. Blue brake discs are scorched and need replacement. Cracks do not allow for compromises. The tiniest crack in a brake disc is a sign for immediate replacement. The forces working on a brake disc are way too high to turn a blind eye. A tiny crack soon turns into a big crack which can cause the entire disc to break. Grooves are rather common in brake discs. They are a cause of irregular grinding of the brake linings. Nevertheless the grooves should not be too deep. They have a damaging effect on the brake linings and a detrimental effect on the braking performance. The permitted minimum residual thickness can be found on the packaging of the brake disc. Even if it hasn't been fully reached yet, the brake disc must be replaced nevertheless. Safety goes first.

Grinding brake discs?

Grinding the grooves from brake disc used to be standard practise for making the surface smooth again. The amount of work no longer stands in proportion to the prices for new brake discs. As the brake disc must be disassembled anyway, installing a new one is the better option. The use of a grinding device and the professional execution are considerably more expensive than a simple replacement.

Replacement of brake discs

The replacement of brake discs is rather easy. The disc is replaced together with the brake linings. It is fixed to the hub or wheel-bearing housing with a central bolt and four screws. The screws are loosened, the old disc removed, the new disc mounted and fixed. When screwing it tight, the prescribed torque must be used!

Quality goes first!

Brake discs, even those from Bosch, ATE and other branded manufacturers are so cheap that purchase of a cheaper component constitutes a great risk. In this case every extra invested euro is a considerable contribution to driving safely and responsibility.