Safety and Education Committee Report - Archive

Choosing the right tire

The tires on a bicycle can greatly affect its handling and performance Properly selecting tires for your bicycle requires you to consider far more than if it will fit the rim and has sufficient clearance.

The better a tire conforms to the road the greater the traction. Soft rubber gives better traction but wears quicker. Some tires have soft shoulders and hard centers for this reason.

A tire should deflect 10% under load. A tire with a high thread count has finer threads and is more flexible. Some of the energy needed to flex the tire is lost so a flexible tire has a lower rolling resistance than a stiff one. Some tires can take very high pressures (160 psi) and still achieve the proper deflection ratio. The higher the tire pressure the lower the rolling resistance, but insufficient tire flex reduces traction.

Smaller (lighter) tires give higher performance. If a properly inflated (10% deflection) tire gets frequent pinch flats a larger and stiffer tire may be needed. To achieve proper deflection the air pressure should be reduced but the added volume will provide a bigger cushion.

Tread pattern can have a great effect on traction. The more rubber that touches the road the better traction you have. Water and loose surfaces like sand can lift the tire so some gaps in the tread will let the rest of it cut through to the pavement. Compressing the rubber tread takes energy and some of that is lost so the tires with thinnest tread have the lowest rolling resistance. On soft terrain the tire sinks in and knobby tires greatly increase the contact area improving traction. On hard surfaces knobby tires reduce the contact patch dramatically and the unsupported knobs can shift around. On the pavement using knobby tires is a lot like riding on marbles. I think they are unsafe when ridden on the pavement above walking speed. There are some tires on the market with knobby shoulders and flat tread in the center. These tires offer traction in loose dirt and on the pavement but could get real exciting when turning.

Bill Fisk- Safety and Education

Safety and Education Coordinator