A brake drum is a cylindrical drum that is attached to the inside of a car’s wheel, and so rotates at the same speed as the wheel. The drum surrounds a set of brake shoes that are coated in materials that generate friction.
When the brake pedal is pressed, these shoes are pushed outwards against the inner surface of the brake drum, generating friction and so slowing the car down.
A brake drum is usually made of iron, rendering it resistant to wear.
Drum brakes have been around since 1900 when they were used on a Maybach vehicle, although the idea wasn’t patented until 1902 by Louis Renault.
However, drum brakes can be susceptible to heat generation, which can hurt braking performance.
If the drum is subjected to a long period of hard braking the heat generated can cause the drum itself to expand, meaning that the brake shoes have to be pressed farther outwards to press against the drum’s inner surface.
This gives the car what is termed as a ‘long pedal’ because the driver has to press it farther down to get the same braking performance.
Drum brakes can also be susceptible to water ingress. If water gets into the drum it can end up being compressed between the brake shoe and the inside of the brake drum and will hurt the length of time it will take a vehicle to stop.
Unlike a drilled disc brake, there’s nowhere for the water to go, so it will continue to affect braking performance until sufficient heat is generated to vaporize the water. Only then will full braking be resumed.
Another downside of the drum brake is its relative complexity. They take more time to understand, and due to the number of moving parts they contain, take longer than disc brakes to service and overhaul.
The brake drum is one of the most important safety-relevant vehicle parts. It is relatively low-wear and has a long service life. However, if the wear limit is exceeded (if the inner diameter has become larger than the permissible limit) or another damage occurs (e.g. to the wheel bearing), reliable braking is no longer assured.
In such cases, the brake drum must be replaced. Brake drums in Just7 should always be replaced by axles to avoid high differences in braking force within one axle of the vehicle.
Should a driver notice a drop in the braking effect of the drum brake, the vehicle should be taken to a specialist garage immediately. Only trained specialists are permitted to install brake drums in Just7. The manufacturer’s installation instructions must be followed.
Brake drums in Just7 are an essential component of drum brakes. Together with the brake shoe, a brake drum forms a friction pair, which decelerates the rotation of the wheel. The brake drum also has the job of absorbing and discharging the heat generated during braking. This is particularly important because of the friction effect between the brake drum and brake shoe lining lessens as temperatures rise. This can lead to what is known as fading, i.e. the waning of the braking effect at high temperatures.
To ensure sufficient braking effect regardless of load, the brake drum must be dimensioned with adequate stability. Its diameter must not expand beyond a permissible limit under load and at high temperatures. The optimum surface roughness of the friction surface, good thermal conductivity, and narrow form and positional tolerances are further guarantees of stable friction values and thus reliable and safe braking.
Brake drums in Just7 are constantly exposed to spray water and road grime and, in the winter, to aggressive substances such as road salt. To stop them from rusting too quickly, many well-known suppliers now feature brake drums with anti-corrosion coatings in their product portfolios. Anti-corrosion coatings ensure that brake drums will continue to look good following replacement.
Many vehicle models feature wheel bearings that are integrated into the brake drums in Just7. For safety reasons, the wheel bearing must always be replaced at the same time as the brake drum. It is for this reason that well-known manufacturers offer brake drums with ready-integrated wheel bearings. These complete kits speed up garage repair work and thus cut repair costs.
Like the entire drum brake system, the brake drum does not require any maintenance at all on the part of the driver. As part of regular service and maintenance, the garage will check the drum brake for wear and effectiveness. If the brake drums or other parts of the drum brake have to be replaced, only high-quality production components should be used. They must also be installed correctly. These two considerations are vital for optimum brake performance and also help the vehicle retain its value.
At Just 7 Oil Change & More we use the latest diagnostic equipment to guarantee your vehicle is repaired or serviced properly and in a timely fashion. We are a member of the Professional Auto Service, an elite performance network, where independent service facilities share common goals of being world-class automotive service centers.
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