Brake pads squeak. Causes and what to do about it

The squeak of brakes in no way can be called pleasant. Firstly, it is unpleasant at a purely physiological level, and secondly, it is already a signal of defects in the brake system. Especially it concerns the newest cars, produced already in new century, when constructors try in every possible way to make every unit and aggregate work without noise. Let’s analyze together why the pads squeak, how to struggle with the squeaky brakes and what not to do while replacing and repairing.

The new pads squeak. What’s wrong with them

Any extraneous noise in any machine is subconsciously perceived as a malfunction. This is not always the case. For example, when installing even the highest quality brake discs and replacing the pads with the most expensive and famous ones, squeaks are possible. At least, due to the lapping of the disc and pads.

The diametrically opposite situation is when the pads are already asking to be scrapped, but you can not lead to such a situation. It not only threatens with strong repair of brake mechanisms, but also is dangerous. Too worn pads can lead to the fact that the piston of working cylinder will literally fall out because of the increased stroke, the fluid will instantly leak out, and you can forget about the brakes.

Still, let’s imagine the ideal situation when we bought excellent pads, we put them, we lapped them up for the appointed 200-300 km, and the squeak does not cease. It would seem that the complex in the replacement of the pads, with this cope even a beginner. However, it is not so.

To properly install disc brake pads, you need to follow a few precepts from an experienced mechanic. Here they are.

Lubrication of the pads is mandatory

A lot of car owners, servicing them on their own, make a gross mistake on the spot – they put new pads on a dirty caliper. And in many service stations such a puncture is not uncommon, frankly speaking. What certainly does not do at least half of the drivers – they do not lubricate adjacent to the caliper side of the pad.

Lubrication is essential there. It is written about it in detail here.  Anti-squeak paste is not applied for nothing, it has a specific purpose:

1. It removes the squeaking that occurs due to the friction of the back side of the pad against the caliper working area.
2. The most important thing is to isolate the working oscillating circuits of the pad and caliper.

Naturally, if there is no lubrication, the pad rubs the caliper dry, which causes grinding and heavy wear on the back of the pad, scratches and sinks appear. The best pad without lubrication of the back part will start to signal distress after 400-500 km of run.

Even if you do not change the pads yourself, but leave it to the craftsman, you need to check whether the back part is lubricated or not. If the service station wants to charge extra for lubrication of the pads, you should refuse such services, because pad greasing is included in the list of works on replacement in accordance with the technological card. And it does not depend on the model and year of manufacture of the car. 

The public has a mixed attitude towards anti-squeaking pastes, many tend to think that the paste dries out quickly and is of no use. In reality, the paste dries out, but continues to isolate the oscillating circuits where it was applied to the parts.

Anti-squeak plate as the source of the squeak

All modern and not so modern cars have anti-squeak plates on their brake pads. This is a part made of springy steel. The plate is designed to keep the pad at rest, preventing it from shifting during operation.

The problem is that new pads are not sold with plates or they are very rare. The metal plate is not eternal and will deform over time, which naturally affects the position of the pad. This is what can cause squeaks and knocks. An extremely desirable item with every at least second pad replacement is to replace the plates, they are sold separately.

This should definitely be taken into account if the pads are replaced on a car with mileage, bought with hands. It is unknown how many cycles the plates have worked, and not everyone wants to listen to the squeak. The detail costs a penny, but performs a useful function.

The plates must also be positioned correctly. If they are installed skewed, the effect will be just the opposite of what is expected. And even worse. For example, a bent edge of a hastily or carelessly installed plate will simply wedge the pad and caliper, which will cause overheating of the mechanism parts and rapid uneven wear. Lubricate and clean the anti-squeak plates as well.

Servicing caliper guides. How to Lubricate

On all inexpensive cars, the caliper guides just need to be lubricated. There are exceptions, but they apply to cars with caliper open type, where the guides just clean, but do not lubricate.

Separately want to warn car owners who self-service brake system – no copper grease in the calipers can not be used categorically.

However, the pads and calipers will not squeak from the use of copper grease. It is much worse here. Copper grease mostly hurts the calipers, not helps solve problems, and there are plenty of modern guide lubricants for every purse on the market. Every one of them is better than any copper paste.

The fact is that metals of different composition tend to react under the influence of a third ingredient. Copper is an excellent catalyst for this reaction. As a result, we have tightly stuck to each other planes, jammed calipers and regular failures of brakes, if they have not been serviced for a long time. Most of the contact surfaces of metal parts of different composition are simply thoroughly cleaned and degreased, but not lubricated.

By the way, it’s not just about brake calipers and pads, but also about wheel nuts, hub and rim flats. Engineers did not take into account lubrication when tightening, say, wheel nuts, so there may be problems with tightening torque if the seat, nut, and hub are lubricated. 

The brake system maintenance charts require that the hubs be mechanically cleaned of rust. This is a mandatory procedure.

Assemble the caliper correctly and according to the instructions

You’ll agree that we rarely consult the manufacturer’s manual when we do a seemingly simple job like replacing brake pads. For example, do we often pay attention to brake disc wear and evenness, disc runout, and disc thickness? All of these things eat up meters of braking distance, which can be vital.

Modern brake discs must be grinded or replaced when the wear on the evenness of the working plane is no more than 0.3-0.5 mm. It is impossible to measure this accuracy by tactile method, your fingers just can’t feel a groove of 0.4 mm deep, and it’s already a problem. When we visually make sure that the disc is already worn, and these are 1-1.5 mm deep grooves, the disc is simply unusable.

It is also necessary to find out the maximum allowable thickness of the disc wear. This is not just a matter of pad travel, but also of disc weight. Disc thickness plays a key role in braking efficiency, because the thicker the disc, the better the heat caused by friction of the friction lining is dissipated.

A thin disc will easily overheat the brake mechanism, and this is a way to boil fluid and fail the brake pedal.

Let’s summarize the results

The squeaky brake pads themselves are a clear signal of problems in the calipers. Although not always squeaking can lead to a loss of braking quality, in most cases the efficiency is reduced by 5-7%. At the appearance of the first squeaks, no matter, new pads, or already finishing their life, it is highly desirable to disassemble the caliper and check the quality of the assembly, lubrication and a number of other points that we talked about. Have good brakes and smooth roads!