Glossary of Terms

Pneumatic Tires – Rubber tires made of an airtight inner core that is filled with pressurized air. Pneumatic tires can be made as “Tubeless” (TL) and “Tube Type” (TT):

  • Tubeless Tires (TL) – Pneumatic tires that do not require an inner tube to retain air pressure.
  • Tube Type Tires (TT) – Pneumatic tires that require an inner tube to retain air pressure.

Semi-Pneumatic Tires – Rubber tires that have a hollow center, but do not use pressurized air for structural support.

Flat-Free Tires – Tires that offer similar performance characteristics to pneumatic tires but are flat resistant. Typically, the term flat-free is used to describe tires made of polyurethane.

Solid Tires – Rubber tires similar in construction to semi-pneumatic tires, but without a hollow center.

Bearing – An anti-friction device that commonly uses balls or rollers held between inner and outer races. Designed to reduce friction between moving parts while providing support for the shaft. Common types of bearings are roller bearings and ball bearings.

Bushing – Similar in application to a bearing, but a bushing has no moving parts. Bushings are typically made out of powdered metal or plastic and used as a low-cost and performance option compared to roller bearings or ball bearings.

Hub – Center part of a wheel through which the axle passes.

Ply Rating – Plies are layers of relatively inextensible cords embedded in the rubber of a pneumatic tire to hold its shape by preventing the rubber from stretching in response to the internal pressure. The ply rating affects the load capacity and maximum inflation pressure of the tire.

Bead Seat – The bead is that part of the tire that contacts the rim and creates an airtight seal. The bead is typically reinforced with steel wire and compounded of high strength, low flexibility rubber. The bead seats tightly against the rim to ensure that a tubeless tire holds air without leakage.

Inner Tube – Torus-shaped balloons made from rubber, to prevent air leakage. Inner tubes are inserted into a pneumatic tire and inflated to retain air pressure.

Tread Pattern – The tread is the part of the tire that comes in contact with the ground to provide traction. Various tread patterns are available for each application.