Temperatures reaching 600 degrees centigrade, mechanical strains, and sudden changes of driving conditions - brake discs are exposed to a particularly harsh operating environment. This is why you must not cut corners here. For your own safety.
All drivers should follow this principle, irrespective of how old their car is. Good quality brake discs work efficiently with brake pads, ensuring a short and effective stopping distance.
A car going 100 km/h should, in the event of sudden braking, decelerate in a couple of seconds. In such case, brakes transform kinetic energy into thermal energy. The rotational speed of wheels decreases as they are squeezed by brake pads fitted in callipers. Consequently, brake discs operate in very difficult conditions: high and low temperature, braking and sudden cooling, e.g. when driving over puddles, and extreme mechanical strains.
These threats have a huge impact on the materials. Cheaper brake discs are made of pearlitic cast iron, which is susceptible to corrosion. When exposed to sudden temperature changes, i.e. heating up during braking, followed by cooling down, cast iron is vulnerable to deformation. This is why a good idea is to use more durable discs, made of high quality steel. You can also apply a more advanced technology, namely ceramic discs, made of carbon composites. They are capable of withstanding extremely high temperatures, but they are also much more expensive than the standard discs.
As brake discs must be highly effective when exposed to high temperatures and capable of quickly cooling down, the designers have created an alternative for the traditional discs - ventilated and drilled discs. How do they differ from the standard ones? Ventilated discs have special canals enabling them to cool down from the inside following sudden braking. Drilled discs have numerous openings scattered all over their friction surface, allowing them to quickly cool down not only along their perimeter, but also around the openings. Another type of discs are slotted discs, i.e. they have slots scattered over their surface.
How to chose good brake discs
First of all, they must be made of a high quality material, resistant to different weather conditions, strains and temperature changes. But that's not all. Brake discs should be bought only from reputed manufactures. Their quality should be proven by tests or verified based on the opinions of other users.
The options are broad - you can choose from a wide range of economy and cheap models or the most expensive, first-assembly models. Aftermarket discs are certainly cheaper than premium ones, but the braking quality they offer is much worse. Cutting corners here may have fatal consequences for the driver. In the automotive industry quality comes at a price. Strikingly cheaper components are simply fakes hat will never meet our expectations nor ensure safety. In order to be price-competitive, many manufactures use poorer quality material or don't test their products sufficiently for performance in difficult conditions. Better quality brake discs are more expensive but safer. Renowned manufacturers use costly testing systems checking e.g. the thermal resistance to cracks or the pace of wear of brake pad lining.
When to change brake discs
Brake discs wear depends of the driver's driving style, i.e. its dynamics and the proportion between deceleration by engine and traditional braking. A lot depends also on brake pads. Usually a set of discs will run on two or three sets of pads. Assuming that the latter are changed every 20-30 thousand kilometres, brake discs should be replaced with new ones every 60-80 thousand kilometres. Checking the thickness of brake pads is a much better solution than counting kilometres. Each brake disc has a determined, permissible thickness specified on the so-called "collar,"
ranging from 10 to 28 mm, which does not mean, that the thicker the disc the better. The wear of brake discs may not exceed 1 mm on each side, irrespective of their thickness. This is the basic rule that you should stick to.
Replacement: purchasing new discs or reconditioning old ones
In order to replace brake discs, you must remove the wheels and the brake calliper, and unscrew the anchor. Remember to clean the hub before fitting new discs. Brake pads should also be changed each time you change the discs. The old ones, even if still in a good condition, have fine-tuned to the old disc, and not only will soon damage the new one, but will also compromise your safety. Another good idea is to use brake discs and pads of the same brand. Discs from one manufacturer and pads from another may not cooperate effectively.
Instead of buying new discs, you may want to have your old ones reconditioned. This, however, is possible only if a disc's thickness has not changed - the margin is 2 mm. However, if this is the case, it is recommended that you have the disc reconditioned. This way the mechanic will be able to remove any irregularities caused by the old pads. Brake discs should also be reconditioned if they show signs of corrosion.
This will also improve their condition, if warped. If this is the case, the driver feels vibrtions on the steering wheel. Keep in mind, though, that this is only an ad hoc solution. From safety point of view it is always better to fit new discs.
After having brake discs changed or reconditioned, you should initially drive at neutral speeds and avoid sudden braking. New brakes gain their full efficiency after over 100 kilometres.
The cost of removing brake discs and brake pads ranges from PLN 100 to 150. The prices of discs are varied. Standard, non-ventilated discs, compatible with the most popular models, cost several zlotys. But they are not recommended due to their poor quality. Better quality discs that cool down faster may cost between PLN 500 and 600.
Material is not enough
Replacement of brake discs should be performed by professional and proven garages. The driver's and passengers' safety depends on mechanics. It is imperative that only high quality parts are used and that the replacement is performed correctly. Before fitting new discs, one should check the operation of the calliper and hub. If the brakes remain dirty, they will not be efficient. You will feel vibrations and hear irritating sounds.
Replacement of brake discs and a comprehensive check-up of the braking system is possible with the Motointegrator Partner, a chain of nearly five thousand professional and specialized garages offering high-quality services. Use the Motointegrator.pl search engine to find the nearest garage.