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Brake pads Causes of squeaking and dust. Recommendations for use.
Brake pads - this is the main element of the brake system of the car, actively interacting with the brake disc and creating brake acceleration. Brake pads, this is the same consumable as filters, oils and other technical fluids, and one of the most important safety features of the car, driver and passengers.
The service life of the brake pads directly depends on the driving style, the mass of the car, the availability of additional electronic safety systems and the quality of the brake pads used. On average, when operating a car in mixed mode, critical wear of the front pads occurs after 20-30 thousand km., And the rear pads are approximately one and a half times more, because the front brake pads take the largest share of the load.
The conversion of the kinetic energy of wheel rotation into heat released during braking due to friction with the surface of the brake disc is the main function of the brake pads. At the same time, manufacturers of brake pads strive to ensure braking efficiency by maintaining high values of the friction coefficient in a wide temperature range, while maintaining acceptable indicators of reliability and durability of brake pads. In cars, brake pads are structurally made approximately the same - it is a friction material, by means of an adhesive bonding composition, glued to a metal base (substrate). The main difference in all brake pads is the composition of the material of the working surfaces, that is, the chemical and structural composition of the friction clutch (this is the surface that experiences extreme mechanical and thermal stress during braking in contact with the brake disc or drum).
On this basis, four main types of brake pads can be distinguished.
1. Semi-metal brake pads.
The material of the working surface (friction) is a mixture of metals (both ferrous and non-ferrous) with inorganic fillers and graphite. The metal content can reach up to 65%. The advantages of such pads are good indicators of heat transfer and wear resistance (respectively durability), and the disadvantages are a decrease in the service life of the brake disc. Inefficient operation at low temperatures and increased noise.
2. Organic brake pads.
They are made of organic materials (carbon, glass, Kevlar) with a low (not more than 15%) metal content. The main advantages of such brake pads are a quick response ("grip") and low noise. Disadvantages - low wear resistance (soft pads) and the formation of dust.
3. Low metal pads.
They are made using the same technology as organic, but with a high percentage of metal: up to 30%. At the same time, in comparison with organic ones, heat transfer and wear resistance indicators improve, but even more dust appears and the noise level of work increases.
4. Ceramic brake pads.
Friction material - ceramics, using non-ferrous metals or synthetic rubber as fillers. Ceramic brake pads are modern products that meet, first of all, the requirements of the environment (low dust formation). They show the stability of the coefficient of friction over a fairly wide temperature range, provide a sparing mode of operation of the brake discs and a noise level comfortable for the driver. The disadvantages include high cost.
How much do brake pads average? The original (OEM) serves 20-25 thousand km. Analog brake pads (not original) serve 10 - 15 thousand km. How to understand worn out pads or not. There are several indicators for the driver:
1. Most brake pads have a mechanical wear sensor - this is a metal plate that, when the friction material is abraded, contacts the brake disc and emits a squeak or metal rattle. When this sound appears, the pads must be replaced immediately!
2. For a number of cars, electronic wear sensors are built into the pads, which are connected via wire to the car’s self-diagnosis system. In case of friction clutch abrasion, the sensor is exposed and, upon contact with the brake disc, opens the circuit, after which the brake pad wear sensor lights up on the dashboard, indicating that it is necessary to check the brake system.
3. In all cars there is a GTZ tank in which the working brake fluid is located. As the friction clutch wears out on the brake pads, the caliper pistons extend more and more towards the brake discs, pressing on the metal surface of the brake pads. Thus, brake fluid fills brake lines and caliper chambers more and more. Due to this, its level in the GTZ tank becomes smaller and at some point the float circuit breaker lights up the “parking brake” light on the dashboard, making it clear to the driver that the brake system needs diagnostics.
Why can brake pads creak when braking?
Recommendation: always use anti-creak plates and copper anti-creak grease when installing brake pads. Service the brake pads once every six months or once every 10 thousand km.
2. Incorrectly installed brake shoe return springs. And improper installation of the fixing springs in the seats of the caliper.
Recommendation: you must follow the manual for mounting / dismounting brake pads for your car.
3. Caliper guide problems. These guides in their design have rubber seals and anthers that can wear out and crack over time, after which moisture gets inside, the corrosion process begins, and the guide sticks. There is an uneven clamping of the brake pads to the plane of the brake disc. Hence - uneven wear and creaking during braking.
Recommendation: Serve the caliper together with the brake pads, by removing the guides, checking the rubber seals and anthers, removing the old grease and applying new grease.
4. A wedged caliper piston can create a creaking problem. This is when the caliper piston is wedged into any of the braking moments at the extreme point of its maximum operation, pressing the brake shoe against the brake disc. This is due to corrosion on the piston body, which appears due to the hygroscopicity of the brake fluid.
Recommendation: periodic brake fluid replacement in accordance with the regulations will help to avoid this, and revision of the caliper pistons at least once every three years or once every 60 thousand km.
5. Excessively large wear on the brake pads. Their work becomes less efficient due to a bad contact spot with the brake disc, so a creak may be issued.
Recommendation: replace brake pads.
6. Wear of brake discs does not allow effective use of brake pads in a pair of friction. Due to the developed collars on the brake discs, an unpleasant creak is generated from the brake pad.
Recommendation: replace the brake disc.
7. With the new brake discs, the old brake pads are installed. It is unacceptable. If you change the brake discs, then you must necessarily put in new brake pads.
Recommendation: Install new brake pads together with brake discs.
8. Asian brake pads are not paired with Asian brake discs. In this case, there may not be predicted wear of the brake pads and / or discs, and not predicted compatibility of the roughness of two friction pairs, as a result, a creak may occur.
9. Overheating of the brake pads, as a result of which the friction material changes its structure and subsequently, when braking, the shoe begins to creak.
Recommendation: replace the brake pads by checking the operation of the guide calipers, the operation of the caliper pistons, the presence of anti-creak plates and anti-creak grease.
10. Poor friction material in the brake pads. Of course, this fact takes place to be, but its probability is very low. The whole party would creak. Each manufacturer before shipment carries out selective quality control of brake pads. If discrepancies are detected, then the entire article is checked, if it is repeated, then the whole article is rejected and the entire batch is checked. That is, the output from the manufacturer of low-quality goods is excluded.
1. All of the above ten points without fail can make the block dust.
2. Dust may be normal due to the use of certain friction material.
3. High-speed extreme riding provokes dust formation of brake pads.
4. Overheating of the brake pads, as a result of a change in the friction clutch structure, including making the brake pad dust.
5. Brake discs, as part of a friction pair, including wear and dust. Please do not forget about this, especially if the brake disc is worn.
6. Dust is, in principle, normal for a pair of friction, the friction from the brake pads when working together with the brake disc is abraded. Otherwise, the brake pads would be eternal. Do not forget that this is a consumable.
Recommendations: evaluate the nature of your riding style. In 95% of cases, the problem is solved when changing the driving style to a less aggressive one.