Drop Center bolt for side pull caliper Front
A "drop bolt" is a special centerbolt for a caliper brake, which is off-center to allow the brake caliper to reach farther down from the mounting hole than it is intended to. Drop bolts are commonly used when a bicycle is equipped with smaller diameter wheels than it was designed for, most often when substituting 622 mm (700C) wheels for 630 mm (27 inch) wheels.