Brake drum (rear brakes) rear and front for different automobiles
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Your Brake drum (rear brakes) worn out? » Read more about common malfunctions • Repair • Replacement manual
The brake drum is a component of the drum brake. This brake system has been around for many years, prevailing because of its robustness and life span although the trend is developing increasingly towards disc brakes. Despite its resilience a defect cannot be excluded and even though it is no longer the main brake, this should not be ignored. In case of malfunction, a potentially longer braking path and total stopping distance can cause serious accidents.
Where to find brake drum
- Drum brakes are nowadays only used on the rear axle. Start by looking there.
- On a mounted wheel, the brake drum is hidden behind the wheel rim and the tyre. Once both are removed, you find the wheel brake cylinder, brake shoes and both brake linings at the front, the actual brake drum surrounding them as a housing.
How does it function?
- A brake manoeuvre increases the pressure in the wheel brake cylinder, setting its internal pistons in motion. These are directly connected to the brake shoes which are as a result pressed in the direction of the brake drum. The linings attached to the brake shoes come into contact with the drum, causing friction. The built-up momentum decreases and the car halts.
What happens in case of defect?
- Both disc and drum brakes are equipped with a control system. Check lights on the dashboard warn in case of problems.
- A defect rarely occurs on both sides simultaneously. The car pulls to one side or possibly jack-knifes when braking. A sudden deterioration of the braking performance is another typical symptom.
- The parking brake is malfunctioning.
- If the brake drum is rusty, brake fluid could leak out, causing visible dark spots around the affected areas.
- Age often affects the material. Dirt and weather cause corrosion, inexorably eating away the metal until holes develop. Many brake drums have a "brake ring". This internal component too can be affected by rust, impairing the brake power.
- High mechanical stress can lead to cold deformation. This happens in case of accidents, though other causes are likely. The brake drum can become out of round, start vibrating or completely lose brake power.
To the garage or DIY replacement?
- The drum brake is a safety-relevant component, its functioning essential with regard to MOT inspection. Repairs must be performed by a professional mechanic for reasons of insurance. Unprofessionally installed brakes lead to driving suspension.
Extend life span – clean vitrified brakes
Copper, messing, molybdenum, zinc sulphide – brake linings consist of a complex material mix, each with its own melting point. If the melting point of a specific material has been reached, while the ones with the higher melting point maintain their crystalline structure, a hard glassy layer develops on top of the lining, considerably affecting its friction power. This so-called vitrifying occurs specifically in urban traffic, where as a result of permanent "stop-and-go", the brakes are continuously being only partly used. There is no immediate reason for replacing vitrified brakes. Often it is sufficient to cause the brake linings to reach the right temperature to literally "melt away" the vitrified layer. To do this, find a car park or straight road (mind the other traffic!), sufficiently long to maintain a speed of at least 80 km/h (c. 50 mph). Then, step on the brake and repeat this procedure until the braking performance noticeably improves. Additionally, the gradual disappearance of the milky-white layer on the brake pads can be seen.
How much should I invest?
The brake drum provides up to 25% of the total braking power at most. Nevertheless it can make the difference between an accident and a near-accident. Manufacturers promise for their more expensive products a constant braking performance for the entire life span of many years. Depending on whether they are sold with or without wheel bearing, brake drums can cost between approximately 70 EUR (c. £62) and 250 EUR (c. £220). Everybody wants a longer life span and a better braking performance for the drum brakes. Prices can therefore rise considerably. To prevent this, we invite you to take a look in our shop first. We offer premium products at low prices, enabling you to save a lot of money with our offers of the day and permanent discounts.