Secure mounting of the front brake is very important. The fork crown is strong enough that it will not crush if the nut at the rear is attached using only a flat washer or lockwasher. If the mounting surface of the front brake is not radiused to fit the fork crown, a washer with a larger radius may be needed to support the brake and avoid unnecessary stress on the brake bolt. When a rear brake mounts to a curved surface on the brake bridge, you must use radiused washers (as shown in the photo below) to avoid crushing the brake bridge. Traditionally, these bolts have been long enough to protrude all the way through, to be secured by a normal hex nut and associated washers. For instance, the Shimano 600 caliper shown has a 47 - 57 mm reach range.Ĭaliper brakes have a center bolt 6 mm or 1/4" in diameter, which fits through a matching holes in the fork crown or brake bridge of the frame. Many newer brakes have the reach dimension marked on the back. Long-reach dual-pivot and centerpull brakes also are made. If you need a brake with longer reach, you can effectively extend the reach by using a drop bolt. This has become the de-facto standard for "road" calipers, and can now be considered "normal", though it is also correct to call it "short." As fashion has changed, the 47-57 mm size that used to be "normal" has become "long" and the longer-reach calipers have become nearly extinct, aside from very long BMX calipers.Ĭurrently, "short-reach" calipers usually offer a range of 39-49 mm. Some people refer to "short-reach" "normal-reach" and "long-reach" calipers, but this is a recipe for confusion, and such terminology should be avoided. This fork and rim combination call for a brake caliper that can be adjusted to provide a 45 mm reach. As shown, with the brake shoe adjusted all the way up, it measures 39 mm from the center of the bolt to the center of the brake pad. This caliper has a reach range of 39-49 mm. Cantilever brakes and disk brakes avoid these problems, though they have other problems. Long-reach brakes must be of especially stout construction and have long arm extension between the pivot and to the cable attachment to overcome these problems. Generally, shorter-reach brakes work better, due to the reduced potential for flex and the higher mechanical advantage. The reach required for a particular installation depends on the frame construction (how low the brake mounting holes are) and the rim diameter. There has been a historical trend toward shorter-reach brakes, as newer bicycles, particularly racing-style road bikes, are designed for use with narrow tires and without clearance for fenders. Reach dimensions can run anywhere from 39-108 mm. Reach is commonly expressed as a range (allowing for the fact that the brake shoes are adjustable, typically 10-15 mm). This is measured from the centerline of the center bolt diagonally down to the middle of the brake shoe.
Reach is the effective length of the arms of a caliper brake.
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