Dual-caliper brakes are used on many recreational and competition bikes. Unlike coaster brakes that operate by reverse pressure on the pedals, caliper brakes operate by pressure that's transmitted through a cable when you squeeze the hand lever. The disadvantage of dual-caliper brakes is reduced performance in wet conditions. Advantages are reliable braking in most conditions and relatively low maintenance.
Description
Dual-caliper brakes operate on the same principle as other caliper brakes, but the left- and right-side caliper arms move on separate pivots. Depending on the type of bike, such as road bikes or mountain bikes, the additional pivot is part of the caliper arm assembly or is attached to a post on the bicycle frame. Each caliper arm has a brake pad and the main brake arm has a fitting where the brake cable attaches. The secondary arm reacts in conjunction with the movement of the main arm when you apply the brake. Unlike traditional caliper brakes that force the brake pads against the wheel rim on a lateral line, the design of dual-caliper brakes requires the brake pads to be offset of a lateral line. When you apply the brakes, the main arm moves directly toward the rim and the secondary arm moves upward toward the opposite side of the rim.
Braking
Several considerations must be acknowledged when riding a bike with dual-caliper brakes for the first time. Your primary consideration is applying the front and rear brakes in unison to avoid a spill or loosing your balance. If you apply the rear brake alone at high speed, the rear wheel can loose traction, causing the rear of the bike to skid sideways. Squeezing the front lever with full force without using the rear brake transmits your momentum to the front wheel, which could elevate the rear of the bike off the ground. The other consideration for first-time riders is anticipating braking situations. This allows you to brake slowly without interrupting your balance or loosing traction at either wheel if the unexpected happens suddenly.
Maintenance
The dual-caliper arm assembly is the most durable component of the brake system. Barring damage from impact, caliper arms remain in good working order with periodic lubrication of the pivots. Brake pads require periodic alignment and are replaced when they become worn. Brake cables are made from stranded steel wire that's protected in a flexible housing. Maintenance consists of lubricating and adjusting the cables periodically and checking to make sure a cable isn't cut or badly bent. The location of the hand levers makes them vulnerable to damage from impact and spills. Aside from replacing a damaged lever, lubricating the pivot where the lever connects to the handlebar assembly and checking to make sure the bar-clamp bolts are tight are all that's necessary.
Replacing Components
For the average DIY bike enthusiast, removing and replacing the components of a dual-caliper brake system is relatively straightforward. Prominent manufacturers, such as Shimano and SRAM, provide installation and adjustment instructions with their components. You can find informative tutorials on technical websites as well. It's always a good idea to keep spare brake cables, brake pads, lubricant and metric tools on hand to avoid down time and the cost of a shop repair.
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