Radial tyre

In a radial tyre the carcass cords run from bead to bead at roughly 90° to the direction of travel. Because the sidewalls are flexible, a belt (usually steel or aramid) is placed under the tread to keep its shape and diameter stable. In a bias-ply (cross-ply) tyre the layers cross each other diagonally instead.

Radials run cooler, give a larger and more consistent contact patch and handle better at speed, so almost all modern sport, touring and naked bikes use them. Bias-ply tyres remain common on classics, cruisers, small bikes, scooters, off-road bikes and many ATVs, where a stiffer sidewall and load capacity matter more.

Always fit the construction and size listed for your bike, and do not mix radial and bias-ply tyres front and rear unless the manufacturer approves it.