HQ-WB REAR DRUM BRAKE KIT – #BKH-200

Test rendering of a drum brake, made by  in  and rendered in . See  for details.

ACDelco 18B134 Professional Rear Brake Drum Assembly

$30.62
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  • Rear drum brakes are typically of a design (for non-servo systems), or primary/secondary (for duo servo systems) the shoes being moved by a single double-acting and hinged at the same point. In this design, one of the brake shoes always experiences the self-applying effect, irrespective of whether the vehicle is moving forwards or backwards. This is particularly useful on the rear brakes, where the parking brake (handbrake or footbrake) must exert enough force to stop the vehicle from traveling backwards and hold it on a slope. Provided the contact area of the brake shoes is large enough, which isn't always the case, the self-applying effect can securely hold a vehicle when the weight is transferred to the rear brakes due to the incline of a slope or the reverse direction of motion. A further advantage of using a single hydraulic cylinder on the rear is that the opposite pivot may be made in the form of a double-lobed that is rotated by the action of the system.

    Front drum brakes may be of either design in practice, but the design is more effective. This design uses two actuating cylinders arranged so that both shoes use the self-applying characteristic when the vehicle is moving forwards. The brake shoes pivot at opposite points to each other. This gives the maximum possible braking when moving forwards, but is not so effective when the vehicle is traveling in reverse.

  • Drum brakes have a natural "self-applying" characteristic, better known as "self-energizing." The rotation of the drum can drag either one or both of the shoes into the friction surface, causing the brakes to bite harder, which increases the force holding them together. This increases the stopping power without any additional effort being expended by the driver, but it does make it harder for the driver to modulate the brake's sensitivity. It also makes the brake more sensitive to , as a decrease in brake friction also reduces the amount of brake assist.

    In the United States, the (manufactured by ) was the final automobile (produced for the United States Postal Service) to use front drum brakes when it was phased out in 1984. However, drum brakes are still often used for , as it has proven very difficult to design a disc brake suitable for holding a parked car[]. Moreover, it is very easy to fit a drum handbrake a disc brake so that one unit serves as both service brake and handbrake.

    Design Tip: With hard use, brake "fade" can occur eventually. Brake fade is the gradual loss of brake stopping power during prolonged or strenuous use. Very high temperatures occur at the brake drum, and that causes deterioration in the frictional value of the lining or pad material. This is common in drum brakes.

  • Exploded-view of disc brake assembly with caliper, brake pads and rotor

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    Exploded-view of car drum brake assembly with brake shoes, wheel hub and springs

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    Disc brake with caliper and rotor

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    In 1953, fielded three cars equipped with at , where they won, in large part due to their superior braking over drum-equipped rivals. This spelled the beginning of the crossover of drum brakes to disc brakes in passenger cars. From 1955 to the 1970s, disc brakes gradually replaced drum brakes on the front wheels of cars. Now practically all cars use disc brakes on the front wheels, and many use disc brakes on all four wheels.

How Drum Brakes Work | HowStuffWorks

While a "yes" answer would certainly be great for increasing Town Hall traffic, the truth is that today's disc/drum setups are completely adequate for the majority of new cars. Remember that both disc and drum brake design has been vastly improved in the last 20 years. In fact, the current rear drum brake systems on today's cars would provide better stopping performance then the front disc setups of the '70s. And today's front disc brakes are truly exceptional in terms of stopping power. Combined with the fact that between 60 and 90 percent of a vehicle's stopping power comes from the front wheels, it's clear that a well-designed, modern drum brake is all that's required for most rear wheel brake duty.