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A bead breaker is a tool used to remove tires from rims on automobiles and other vehicles. This tool is sometimes known as a bead buster or tire lever, depending on the specific design and intended application. Bicycle tires, for example, can be removed with simple tire levers; these small, plastic levers can be inserted between the tire and the rim and leveraged to pull the bead of the tire off the rim. Larger vehicles require the use of larger bead breaker tools, since the rubber of the tires can be much stiffer and heat and rust can form a seal between the tire and rim.
When a tire is mounted to a rim, the bead of the tire forms a seal between that tire and the rim itself so air can be trapped within. If the tire goes flat for any reason, it must be removed for repair, but the bead may still be bonded with the metal rim. A bead breaker is therefore used to compress the tire, insert a leveraging device between the bead and rim, and lift that bead off the rim without damaging either component. Some bead breaker tools feature hydraulic cylinders to facilitate this movement, while others simply use natural leverage forces.
Motorcycle bead breaker tools are generally smaller than those used on cars, trucks, and other large vehicles, though motorcycle tires can also be difficult to remove. In some cases, a long metal lever can be inserted between the bead and the rim, and it can then be moved around the circumference of the rim to break the entire bead free. Once one side of the tire is free from the rim, the rest of the tire can usually be removed easily, though the tire lever or bead breaker may also need to be used on the second bead as well.
One of the risks run when using a bead breaker is damage to the tire and the rim. If the leverage is exerted directly onto the rim, it can cause pits, divots, burrs, and other damage that can in turn cause damage to the tire and decrease the aesthetic value of the components. The bead of the tire can also be damaged if too much force is exerted upon it. Bicycles usually use tubes inside the tire to hold air, and using a tire lever or breaker can pinch the tube, leading to a flat.