Disc brakes on all four wheels are now standard on modern cars. Drum brakes only serve as a parking brake. Even in compact cars, masses in motion and engine performance are too high for simple drum brakes to guarantee safe braking. Yet, the problem applying to all brakes has a name: brake fade.
Preventing brake fade with high-performance brakes
Brake fade is the loss of braking effect due to accumulated heat in the brake system. If the heat which is generated by a braking manoeuvre cannot be diverted quickly enough, a dangerous situation occurs: the brake disc temperature approaches the melting point and the friction between the brake lining and the brake disc is significantly impaired.
In drum brakes, this often leads to total failure. But also simple, unperforated and one-piece brake discs can cause brake fade. Here too, the cause is the inadequate diversion of accumulated heat.
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Perforated brake discs: be careful and make the right diagnosis
Generally, standard installed brakes are adequate for ordinary use. Even exceptional situations such as long drives downhill are taken into account by manufacturers at construction. The steel of a brake disc has a melting point of 1400°C. You have to brake for a very long time to reach it.
If a short-term failure of the brake system occurs at normal use, it is probably not caused by brake fade. In this case, a defect in the hydraulic system is more likely.
The most evident cause is brake fuel being too old, accumulating too much water. This can be checked with a test strip. If the brake fluid has already turned green, you can save yourself the trouble – the brake fluid must be replaced immediately and the brake system thoroughly vented. Another cause for a sudden loss of brake pressure can be a rupture of the brake line.
Therefore: when the brake becomes unsafe, immediately start looking for the cause. With normal use, brake problems are hardly ever caused by construction faults.
Higher speed, more heat
When the car is pushed to its limits and driven on the racecourse, the standard one-piece brake disc can reach its limits too.
What applies to brakes is the cooler the better.
Therefore engineers continuously work on optimising braking conditions with innovative discs.
One of the options is the perforated brake disc.
Perforated brake discs: More than just holes
It would be too easy to just drill a few holes in the one-piece brake disc and hope for any effect. We have to disappoint the user here – constructing a heat-optimised brake disc takes a lot of ingenuity.
The perforated brake disc can be seen as the next evolutionary step of the internally ventilated brake disc. Although one-piece brake discs can be optimised with slits and holes. These are only allowed on the rear axle and primarily serve optical effects as they cannot be distinguished on sight from the highly strained front-axle brake discs.
The internally ventilated brake disc is a highly complex component. It is constructed in such a way, that during driving air is sucked in through the hub and blown outwards through channels within the brake disc. The air flows over the heated disc, taking the accumulated heat with it.
An internally ventilated brake disc is effective without perforation, too. However, if the brake disc is equipped with minutely placed holes, several positive effects occur:
– optimising heat diversion
– less brake disc abrasion
– weight reduction of the brake disc
– a sporty, dynamic accent for the car.
Disadvantages of perforated brake discs
With the many advantages of perforated brake discs, you would almost not believe that they can have some disadvantages too. Unfortunately, where is light, there is shadow.
For perforated brake discs, higher wear of the brake linings is the main disadvantage. The structured surface of a perforated brake disc works like a grate, wearing brake linings considerably faster than a smooth, one-piece brake disc.
Should you be willing to install perforated brake discs on your car, take into account that you will need to replace the brake linings twice as often. Fortunately, this maintenance is very simple and can quickly be learned.
Be sure to check approval
A perforated brake disc is a highly strained component, which has been structurally weakened. This makes the high quality of construction and finishing necessary. If you are interested in this dynamic and efficient feature, be certain not to economise on the wrong end: perforated brake discs should always be purchased in certified brand quality.
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Therefore, high-grade brand products generally come with a universal certification. Additionally entering the conversion in the registration documents of the car is not necessary for most manufacturers.
Perforated brake discs: Mind the rotating direction
- Particularly important for ventilated brake discs is their installation in the right direction. The air is sucked in by the hub and directed outwards.
- If they are installed the wrong way around, the opposite happens: the cold air is sucked in right outside of the brake disc, heated on its way through the disc and densely blown inwards.
- This causes the development of heat accumulation on the caliper, axle sleeve or ball joint. These components contain a certain amount of rubber, weakening as a result of permanent heating and aging quickly as a consequence.
- Perforated or not, to every conversion or installation of internally ventilated brake discs applies: read and understand the manual thoroughly prior to installation and before unscrewing the first bolt. Only then you are certain of a successful repair, giving you the desired performance upgrade for your car.
Foto: Patrick Thomas, gameanna, Tony Savino, Charles Knowles, Chatchai.wa, trinityfoto, AlexLMX, rawcapPhoto, pdsci, Stason4ik, Aleksandr Kondratov / shutterstock.com