<P> Bicycle tire casing is made of cloth, usually nylon, though cotton and silk have also been used . The casing provides the resistance against stretching necessary to contain the internal air pressure while remaining flexible enough to conform to the ground surface . The thread count of the cloth affects the weight and performance of the tire, and high thread counts are generally preferred . </P> <P> The fibers of the cloth in most bicycle tires are not woven together, but kept in separate plies so that they can move more freely to reduce wear and rolling resistance . They are also usually oriented diagonally, forming bias plies . Radial ply has been attempted, but found to provide undesirable handling characteristics . </P> <P> The tread is the part of the tire that contacts the ground . </P> <Dl> <Dt> Compound </Dt> </Dl>

What does bar mean on a bike tire