Tire bead is the term for the edge of a

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

that sits on the

wheel A wheel is a circular component that is intended to rotate on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six simple machines. Wheels, in conjunction with axles, allow heavy objects to be ...

. Wheels for

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded ...

bicycle A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist. B ...

s, etc. are made with a small slot or groove into which the tire bead sits. When the tire is properly inflated, the

air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars ...

within the tire keeps the bead in this groove. It is common amongst drivers of

off-road vehicle An off-road vehicle, sometimes referred to as an overland or adventure vehicle, is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with de ...

s to decrease the air pressure in their tires. Airing Down for Off Road Driving
/ref> This makes the tread of the tire spread out, creating more surface area for the tire's tread to grip the terrain. If the pressure is too low, there may not be enough pressure to keep the bead on the wheel, thus causing the bead to pop off the wheel; this is often referred to as "losing a bead".

Beadlock A beadlock or bead lock is a mechanical device that secures the bead of a tire to the wheel of a vehicle. Tires and wheels are designed so that when the tire is inflated, the tire pressure pushes the bead of the tire against the inside of the whe ...

s, which clamp the bead on the wheel, are often used in this case. Often, the bead can become frozen to the rim after rusting occurs, requiring the use of a

bead breaker A bead breaker is a tool used for separating tires from rims. The innermost diameter of the tire that interfaces with the rim of a wheel is called the tire bead. The bead is a thicker section of rubber, and is reinforced with braided steel cable ...

References

Tires {{automotive-part-stub