![]() ![]() Shimano has SLR and Super SLR standards, recommending to match brake calipers and levers to the same standard. There are also several types of modern road brake calipers with different cable pull ratios (and mechanical advantage). ![]() ![]() Mechanical disc calipers for MTB work with V-brake levers. There are also specially made road bike disc calipers that work with road brake levers and won’t work well with others. ![]() There are three types of brake levers: V-brake, cantilever, and road levers. They match appropriate brakes with the same name. If the brake lever pulls 10 mm of cable, the brake pads should move about 5 mm, which makes for about 2:1 mechanical advantage. The amount of cable pulled by the lever needs to match the movement of brake pads. This is why mechanical advantage needs to be balanced. Since pads are always at least 1 mm away from the braking surface, too much mechanical advantage results in lever being pulled all the way to the bars and brake pads just reaching the rim, not applying any force, or not even reaching the rim. Braking force would have been great if the pads would touch and rub the rim/brake disc rotor all the time. Too much mechanical advantage leads to a mushy, spongy feeling at the lever, since great force squishes both pads and cable housing. When trying to brake hard with such brakes, the force applied to the brakes will be relatively small, inadequate for effective stopping. The feel on the lever will be firm, but this feeling is misleading. Too little mechanical advantage leads to low braking force. There is more cable pulled, 15 mm for a 20 degree lever rotation – thus providing lower mechanical advantage. Distance from brake cable anchor to pivot around which the lever rotates is 42 mm. So there is less cable pulled, just 7 mm for a 20 degree lever rotation – providing higher mechanical advantage. One pulls 7 mm of cable, the other 15 mm: Distance from brake cable anchor to pivot around which the lever rotates is smaller, only 21 mm. In the pictures below, there are two levers, both with 20 degree travel. This allows user to choose more mechanical advantage, or less, but with more pads movement (for better clearance in mud). V-brakes, road calipers and disc calipers have fixed leverage, while cantilever brakes allow change of mechanical advantage by altering the top cable length and angle. The less distance brake pads move per one mm of cable pulled, the higher mechanical advantage. The less cable is pulled by the brake lever during it’s complete 20 degree travel, the higher mechanical advantage. Brake pads are placed about 1 to 2 mm from the wheel rim, or disc rotor. Brake lever can travel about 20 degrees until it reaches the bars. Lever principle is used for mechanical brakes. Mechanical advantage for mechanical brakes and the amount of lever cable pull However, in order to lift mass M1 for 10 cm, mass M2 will need to cover a larger distance.Ģ. So if lever b is twice longer than lever a (in the picture above), 1 kg of mass M2 will be enough to lift 2 kg of mass M1. Ratio between levers is called mechanical advantage. Also, for moving a great mass over the same distance, the longer the lever, the more distance needs to be covered by the mass used for moving the larger mass. The longer the leverage, the less mass is needed to move a greater mass. Mechanical brakes work on a simple lever principle. Mechanical advantage for mechanical brakes and the amount of lever cable pull.Different post explains brake (and shifter) cable and housing standards. Though I have made a video explaining hydraulic brake working principle. Hydraulic brakes will be explained in a separate article. This post will explain the basic principles of mechanical brakes functioning, i.e. ![]()
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