Cannondale Bicycle Corp. 2000 OM Page 67
Some special high-performance tires have unidirectional treads: their tread
pattern is designed to work better in one direction than in the other. The
sidewall marking of a unidirectional tire will have an arrow showing the cor-
rect rotation direction. If your bike has unidirectional tires, be sure that they
are mounted to rotate in the correct direction.
2. Tire Valves
The tire valve allows air to enter the tire's inner tube under pressure, but
doesn't let it back out unless
you
want it to.
There are primarily two kinds of bicycle tube valves (actually, there are other
designs, but they are seldom seen in the US any more): The Schraeder Valve
and the Presta Valve. The bicycle pump you use must have the fitting appro-
priate to the valve stems on your bicycle.
The Schraeder (Fig. 21a) is like the valve on a car tire. To inflate a
Schraeder valve tube, remove the valve cap and push the air hose or pump
fitting onto the end of the valve stem. To let air out of a Schraeder valve,
depress the pin in the end of the valve stem with the end of a key or other
appropriate object.
63
fig. 21A Schraeder Valve
