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What resource do the brake discs have, and when should you replace them?

Brake discs are one of the most mysterious automotive parts in terms of resources. Some of them have more than 100,000 km, and some should be changed after 20,000 km. In this article, we will review all the factors that affect the lifetime of brake discs.

Disc Brakes

How Long Do Brake Discs Run?

So what is the resource of brake discs, and how is it measured? You may be surprised to hear that these are not kilometers or years. The condition and service life of brake discs can only be measured in millimeters of their thickness. That is why there is no clear or even rough recommendation “when to change disks”. Even with normal driving, the range can vary from 60,000 to 120,000 kilometers. Therefore, it makes no sense to measure the brake disks’ resource in kilometers, and such an approach can be considered incorrect.

However, in the case of disk thickness, each car manufacturer gives clear recommendations:

  • For Passat B5 brake discs: the initial thickness is 25 millimeters and the minimum allowable is 23 mm;
  • For Toyota Corolla – 22 and 19 mm;
  • For Opel Astra G – 24 and 21 mm;
  • For Renault Megane 3 – 25 and 23 mm;
  • For Chevrolet Lacetti – 24 and 22 millimeters.

Determining how much the discs pass after the measurement is relatively easy. If for 40,000 kilometers you have erased 1 millimeter of the thickness of the part, then it means that they will work out another 40,000 kilometers. Alternatively, it is worth looking for new Renault or Toyota auto parts as soon as possible.

How To Measure Brake Disc Wear?

To determine the thickness of the disc, it is necessary to remove the wheel – otherwise, this unit simply cannot be reached. After that, the thickness of the disc can be measured with a vernier caliper or other measuring device that measures with an accuracy of 0.1 mm. This accuracy is necessary because the average disk resource is measured by 2 millimeters. For example, 24 mm is the thickness of a new disc and 22 mm is the disc to be replaced. Therefore, plus or minus a millimeter is crucial.

Why is the thickness of the discs so important? Because this is a heating part – they remove heat with their entire body. If the metal becomes thin (and 2 out of 20 millimeters is already 10% of the total mass), then the disks overheat and deform, up to the appearance of cracks.

Remember, that several factors can affect the brake disks’ life:

The driving style;
The driving mode. For example, if you change your place of residence, and now there are more sections with traffic lights, stops, and braking on your way;
The pads. The composition of the friction mixture is different for each manufacturer and this affects the discs’ wear out;
The quality of the material from which the disc is made.

The service life of the brake disc always depends on you. Therefore, with a careful approach, your discs will cover hundreds of thousands of kilometers.

Categories: Life