• Tread– This is the part you see that hits the road, and the part most people think about. For the most part, smoother tires work better on smooth, dry surfaces, and ‘chunkier’ tires work better off-road. There are special tire designs for snow, ice, and sand.
• Bead– This is the part of the tire that mates to the wheel. It is typically steel wire covered heavily in rubber. The bead has a snug fit to the wheel to prevent the wheel from sliding rotationally in the tire.
• Carcass– Briefly, this is the ‘body’ of the tire under the tread. Motorcycle tires are typically bias-ply or radial, which refers to how the tire is constructed.
Bias-ply tires have belts which are typically cords made of fiber – polyester, aramid, or fiberglass, which run from bead-to-bead on an angle of thirty to forty degrees or so.
Radial ply tires have the casing cords run directly from bead to bead radiating outwards like the spokes of a wheel. Because the cords do not cross each other the casing ismore flexible. The structure is stabilized by a belt formed of layers of cords (which are almost always steel) laid right around the casing just under the tread rubber. The belt cords are placed at a low angle to the centerline of the tread and alternate layers cross each other at angles ranging from 30 to 45'.
• Sidewall– the area of the tire that bridges the tread and bead. A small part of the tire, it is vitally important – it gives the tire much of its handling and load transfer characteristics. This is the part of the tire we’re talking about when we reference height, profile, or aspect ratio. Typically, a shorter sidewall yields a stiffer sidewall, which tends to flex less. To a rider, this means better handling and turning, worse bump absorption, and more difficult mounting. This section greatly contributes to the tire’s role in the suspension. That’s right - the tire is a suspension component!