Brake pads. Part 1: Composition, characteristics and marking

No one would think to argue that brake pads for any car are important. It’s not just about safety. You can also optimize, reduce the cost of car maintenance, with the help of a competent selection of spare parts and consumables. Only for this purpose it is necessary to know as much as possible about the spare parts, so the seller will not be able to shove junk. What are the brake pads, how they are divided by type and design, characteristics and features of each type we discuss right now.

Brake pad design and function

Knowing the construction and composition of the brake pads we install is useful for the reason that it determines not only the effectiveness of the brakes, but also the life of the disc or drum. And it costs a lot more to change them than the pads. A low-quality pad can wear down a disc in one season without the possibility of repair, while a high-quality pad can keep the disc surface for a dozen years.

Structurally, a brake pad consists of a metal base (sometimes polymer compositions are used, but this is not a civilian level of manufacturing), the most important friction layer and a layer of thermal insulation-glue, by means of which the pad is attached to the base. Modern braking systems are equipped with alarm sensors for friction wear.

It may be in the form of an electronic wear sensor or it may be a metal plate. The mechanical wear sensor is set up so that the metal tab is located 3 mm from the base level and when the friction is worn below this level, the tab rubs against the brake disc, making a nasty sound.

This will be the signal that the pads are worn, whistling means it’s time to change.

Conclusion 1: Design and parameters

The brake pads is designed to convert kinetic energy into thermal energy. The heat generated has to escape quickly into the atmosphere, and ventilated disc brakes are available for this purpose. The effectiveness of the pad depends on the composition of the friction lining. A bad pad wipes out the brake disc.

There must be at least a mechanical wear sensor on the pad. Quality pads have an anti-noise and anti-corrosion coating on the back of the metal plate. The friction must have a groove for the removal of dust and heat from the working area of contact with the disc. This will ensure even wear of both the disc and the pad itself.

Какие колодки лучше. Виды фрикционных накладок

Visually, pads for one car model may be quite the same, differing only in marking or design refinements of this or that company. The main difference between the pads is in the composition of the friction layer.

The quality of the pad also depends on it. Of course, pad manufacturers will never reveal their secrets or name the exact composition of the friction lining. Nevertheless, they must ensure at least the absence of harmful asbestos in the composition.

The most common types of overlays used on civilian cars are as follows:

Half-metal pads. The most common and most inexpensive type of pads. The friction contains from 30 to 60 percent of metals in the form of chips, wires, copper powder, iron. All of this is filled with a graphite composite for bonding. These pads wear out relatively quickly, can also erode the brake disc quickly, are noisy, and have poor frictional performance in cold weather.

Organic pads (NonAsbestos). The pad is made from fibers of organic materials. It can be glass, kevlar, carbon fibers, rubber. Composite resins that can withstand high temperatures are used as a binder component. These pads are soft, and silent, but they are very dusty and wear out very quickly.

Low-metal organic. The composition of the pad is determined by the amount of metal inclusions in the organic compounds. In fact, they are the same organic pads, but with 30-50% copper or steel dust and shavings. The coefficient of friction increases, but so does the noise level. Good for those with an aggressive driving style.

Ceramic. The most progressive type of pads. The basis of the pad is ceramic fibers. The composition may contain a small amount of metal powder. Very light, with almost no dust, which contributes to minimizing wear of the brake disc. The coefficient of friction is twice that of the classic half-metal pad. In terms of noise level, they are positioned as the quietest. Price is the highest on the market.

Below is a table with the characteristics of each type of pad and examples of applications.

Conclusion 2: Brake pad type

When choosing the type of brake pads, we will not consider only the price per set. This is short-sighted, because by saving a dollar or two on a set, we first risk ruining the brake disc, and second, get a squeaky, dusty, and ineffective pad.

The type of pad is chosen strictly on an individual basis. Some people are quite satisfied with the classic type, and it can serve for the longest time. Others will wipe it into powder in two months and curse the manufacturer. In vain.

Because the main thing in this matter is the operating conditions and driving style. Cheap half-metal pads are not suitable for an extremely aggressive style. Apart from the fact that they will overheat and dust, they will wear out very quickly.

Conversely, for a relaxed driver, there is nothing better than a soft and quiet pad that will not overheat in his speedway and will last long and efficiently. An example of this is the table above.

Marking of brake pads

To help us understand the types of friction material without resorting to laboratory research, the manufacturer labels the pads according to several parameters – the type of use, the composition of the friction mixture, and the maximum operating temperature.

Marking by operating temperature

The easiest way to do color coding. There are no unified rigid standards in this regard, but in general decent manufacturers adhere to such classification:

1. Black pads. The simplest type, for everyday use. The operating temperature range does not exceed 400 °C.
2. The green color of the pad base indicates that the friction can withstand overheating in the range of 600-650 °C.
3. Red pad. Used for racing and sports cars, the maximum operating temperature is 750 degrees.
4. Yellow pad indicates the possibility of use in heavy road conditions, track racing, ring, street racing, the maximum temperature is 900 degrees.
5. Blue or blue pads have the same characteristics.
6. Track highly specialized pads are colored orange. The maximum operating temperature is at least 1000 degrees Celsius.

Friction coefficient marking

And yet, the main indicator that we will pay attention to when choosing a pad is the coefficient of friction. It is indicated by the letter μ in the specifications, and on the pad itself – by a code.

The point is that the μ value is not constant, it varies depending on changes in temperature of the working surface at the point of contact with the disc, on humidity and mass of other factors.

The table below shows the values of μ and the corresponding letters in the marking of the pad.

Typically, this value is indicated at the end of the pad code as two letters. The first indicates μ at a temperature of about 95 degrees, the second – at 316 °C. The marking can be found on the back of the pad where its catalog number (article number) is indicated.

In addition to the basic data on the back of the pad we find:

Let’s summarize

This is the basis without which a deliberate choice of brake pad is impossible. Yes, we can take the seller’s advice into account, but his competence in this matter may be highly questionable. In addition, he is interested in shoving us stale and unpopular goods. This is the specifics of the work.

We have understood the basic concepts and basic principles of how to choose the right pads. However, there are a lot of nuances that should be considered and how not to choose a fake, and how to buy a good quality pad cheap, read the following materials of the I Love My Car Club. Good Brakes to everyone and smooth roads!