Nothing can be more irritating than a permanent, silent “squeak-squeak-squeak” coming from the wheel arches. The most common reason for this sound is the squeaky brakes. The good news: with a bit of expertise you be can eliminate this error yourself. Though be sure to make yourself acquainted with the disc brake mechanism as only brake discs and their brake linings cause these problems.
Disc brake construction
Nowadays, the disc brake has become standard on all four wheels of all new cars. It is more reliable, effective and less prone to wear than its predecessor, the drum brake. Above all, disc brakes are safer. Contrary to drum brakes they do not fail as a result of heat accumulation.
A brake disc consists of a disc brake and the caliper with its integrated brake linings. A driver stepping on the brake pedal causes the brake cylinders in the caliper to extend, pressing the brake linings against the rotating brake disc, initiating the brake effect. Brake disc and brake linings are wear parts, gradually wearing out.
Generally, the brake disc should be replaced on occasion of every second brake lining replacement and should always be checked at every brake maintenance. Furrows, ripples or reaching the minimal thickness are clear indications for immediate replacement.
This point can be the cause of the squeak; a rippling brake disc has bulging spots, grinding against the brake linings – making the brake squeak.
Loose bearings as a main cause
- The main cause for squeaky brakes lies in the installation. Often, other than original or certified spare parts were on occasion of the last repair. We specifically advise against this when it comes to brakes: only brake bearings and discs approved by manufacturers guarantee full braking effect and a sufficient life span.
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- No-brand products from the internet do not offer these. Material condition and the right fit is not guaranteed with cheap spare parts. Saving a few bob here can have expensive and fatal consequences. Squeaky brakes would then be the least of your problems.
- Often, a squeaky brake results from negligence or ignorance at installation. The many moving parts of a brake need lubrication in order to interact properly. This applies especially to the brake linings. They must be able to smoothly glide in their holders to prevent them from jamming or uneven and untimely wear. Until then, they make themselves noticed by squeaking.
Use suitable lubricant
When hearing the word ‘lubricant’ many people think of oil and grease. Let’s be clear: neither of these belong on the brake. Treating a squeaky brake with oil or grease is crossing the line of negligence by far, rendering the brakes practically ineffective and probably resulting in either a serious accident or repair.
The only right lubricant for brakes is copper paste. The paste is applied to the back of the brake bearings prior to inserting them in the caliper.
The caliper can use some copper past on the brake cylinder as well. This allows the bearing to glide in the caliper properly lubricated without compromising the brake effect.
Prior to assembly of the brake the entire part is liberally sprayed and cleaned with brake cleaner. This prevents alien particles from interfering with brake operation.
Squeaky brakes after long standing
A squeaky brake disc can also be caused by corrosion. Brake disc are under high strain. They need to be sufficiently sturdy and tough to ensure the full braking effect until reaching the wear limit.
What brake discs do not offer is corrosion protection. Actually, anti-corrosion and brake effect rule each other out. Theoretically it is possible to build brake discs using stainless steel. These would however be too brittle and break under high strain.
Manufacturers therefore put their trust in the self-cleaning properties of the brake discs. A regular application of the brakes will cause brake discs to grind themselves clean by undergoing friction. This is why brakes always look so shiny.
If a car remains stationary for a long time, corrosion can attack the brake discs. Up to a certain point, their material sturdiness and more or less rain-secure location keep the progress in check. Nevertheless, the normal air moisture is enough to cause rust spots on the clean brake discs.
It is important, that this rust is scoured off. If this is not done carefully, you run the risk of ruining the brake system. Attempting to grind a brake disc clean by driving at high speed and braking strongly can have fatal consequences: the loose rust flakes are scoured off and penetrate the brake disc and the brake linings. The resulting furrows make the wear parts of a brake system useless and fit for replacement.
- If the brake disc is strongly corroded, the wheel must be removed and the worst rust sanded off with sand paper.
- When the rust is removed save for a few slight spots, the brake is ready for self-cleaning. This makes sense as long as the the brake disc is sufficiently thick. The required thickness of the brake disc can be found in the repair documents of the car model.
- The self cleaning is done as follows: drive as slowly as possible and brake carefully. By gradually speeding up and applying more brake pressure, the brake disc is gradually scoured clean.
- Subsequently the brake must be profoundly rinsed with brake cleaner. Now the squeak should be gone.
Distinguishing squeaking from grinding
This article concerns the squeak-squeak-squeak noise, heard during driving as described in the introduction.
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It is important to tell the difference from grinding and scratching, only occurring when stepping on the brake pedal. In this case, the brake lining is definitely worn. The car must be driven to the garage immediately as it is no longer fully safe with worn brake linings.
If this symptom occurs, be certain to drive slowly and carefully. Ideally the car is towed away, which we emphatically recommend here.
Squeaky brakes when driving backwards
or after changing tyres
- In some cases, squeaky brakes occur after a change of tyres. This can happen when the size of the tyres was changed. To solve this greatly depends on the car model. Some products require bevelling of the brake linings.
- A squeak when driving backwards does not necessarily come from the brake linings. It can be a sign of a worn clutch. Even the dynamo can produce a sound when its bearings are worn. Prior to repair, a profound error search is necessary.
- For the brakes proceed as follows: drive on a slope and let the car roll down it. During descent, switch off the engine. All systems including the dynamo are now off. If the squeak is still audible, you can narrow it down to the brakes.
However, take care:
- When the engine is switched off, it quickly loses brake pressure. This test should only last a few seconds. Then the engine should be started again. Furthermore, although the engine is switched off for this test, the key should be in ignition position. The brake light remains active despite disengaged engine and traffic participants behind you will not become irritated so soon. Tests such as these are better performed under conditions of as little traffic as possible.
In case of doubt, go to the garage
If you are uncertain with regard to the cause and the repair of squeaky brakes, do not hesitate to visit the nearest garage. Only then you have maximum certainty and safety with a professional repair.
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