My car dictionary

Brake drums 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 the friction effect between 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.

Structure of the brake drum

In order 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. 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 are constantly exposed to spray water and road grime and, in the winter, to aggressive substances such as road salt. To stop them 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 which are integrated into the brake drums. 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.