08 July, 2011
What Are Rollerbrakes on a Bicycle?
Rollerbrakes are the Shimano-branded name for drum brakes on bicycles. An optional install on Shimano bikes, the Rollerbrake is often installed inside the internal gear and front hubs of compatible Shimano bikes. Drum brakes are hand-operated and are much heaver than other types of bicycle brakes. Unlike standard bike brakes that push along the wheel rim to slow down the bike, drum brakes have brake shoes that press against the inside of a “drum,” hence their name.
Rollerbrakes are cable-operated with metal braking surfaces that are then lubricated with bike grease. Set inside a cylindrical casing, the cam and rollers are fully covered. The cooling disc for the brakes -- to reduce the chance of overheating -- and the brake arm for the cable is kept outside of the casing. Rollerbrakes are distinctive for their many rollers rather than the more common two roller set of leading and trailing shoe.
How It Works
As your hands squeeze the brake lever, the rollers inside the housing get pushed outwards by the cam, placing pressure on the casing. The casing then engages the shoe, causing your wheel to slow down. As there is significant friction generated, there is a slight heat build-up in the brake, which is reduced by the cooling disc. The cooling disc rotates to catch the air from the cutouts to keep it circulating.
Drum brakes are generally uncommon on bicycles because of their weight. However, the Rollerbrake is made to be lighter than traditional drum brakes, and it is well-suited for urban biking when there are not many steep hills. Rollerbrakes also differ from traditional drum brakes because only the Rollerbrake needs to be replaced if the drum becomes worn. Traditional drum brakes often need to have the entire wheel replaced. Rollerbrakes also are weather proof because of their encasing, meaning there is significantly less maintenance required.
Although Rollerbrakes are lighter than traditional drum brakes, there is still a significant weight increase involved. In some cases, as with tandem bicycles, the extra weight may actually be a benefit as it provides greater stability. However, for single-rider bicycles, particularly road bikes that are designed for lightness and speed, the extra weight is a deterrent. Because Rollerbrakes are a Shimano-designed drum brake, they are only compatible with certain Shimano-brand bicycles. And Rollerbrakes can experience significant overheating during long, steep descents, as the extra friction generated is only dissipated somewhat by the cooling disc.
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