Why do car tires not need a tube or liquid sealant but bicycle tires do?

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Why do car tires not need a tube or liquid sealant but bicycle tires do?

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Whether or not a tire requires a tube depends on the type tire and wheel used. Automobiles don’t need tubes because both the tires and wheels are designed to hold air without them.

Most bicycles still require tubes, but you can buy bicycle wheels and tires that do not. They call them “tubeless”, and they’re very popular amongst riders who spend a lot of time off-road. Most cyclists run sealant for convenience (to automatically seal punctures), but you don’t necessarily *have* to run sealant if you don’t want to.

Bicycle tires will leak down faster though, because the rubber is much thinner and the bead is much longer (bicycle rims are often close to 29″ in diameter. A very large car wheel is 22″ in diameter. The tire leaks around the circumference of the bead, which grows at a rate of 3.14159 times the diameter. This means that for every inch of diameter you add, you get more than 3 inches of circumference along which the tire will leak. Hence, most bicycle tires strongly recommend sealant to make them more air tight.

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