Schwinn none - Manual (Page 88)

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Tire pressure is given either as maximum pressure or as a pressure range. How a tire performs under different terrain or weather condi-
tions depends largely on tire pressure. Inflating the tire to near its maximum recommended pressure gives the lowest rolling resistance;
but also produces the harshest ride. High pressures work best on smooth, dry pavement. Very low pressures, at the bottom of the recom-
mended pressure range, give the best performance on smooth, slick terrain such as hard-packed clay, and on deep, loose surfaces such
as deep, dry sand. Tire pressure that is too low for your weight and the riding conditions can cause a puncture of the tube by allowing the
tire to deform sufficiently to pinch the inner tube between the rim and the riding surface.
CAUTION: Pencil type automotive tire gauges and gas station air hose pressure settings can be inaccurate and should not be relied
upon for consistent, accurate pressure readings. Instead, use a high quality dial gauge.
Ask your dealer to recommend the best tire pressure for the kind of riding you will most often do, and have the dealer inflate your tires to
that pressure. Then, check inflation as described in so you’ll know how correctly inflated tires should look and feel. Some tires may need
to be brought up to pressure every week or two.
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 correct 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 appropriate to the valve stems on your bicycle.
The Schraeder 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 fit-
ting 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.
The Presta valve has a narrower diameter and is only found on bicycle tires. To inflate a Presta valve tube using a Presta headed bicycle
pump, remove the valve cap; unscrew (counterclockwise) the valve stem lock nut; and push down on the valve stem to free it up. Then
push the pump head on to the valve head, and inflate. To inflate a Presta valve with a gas station air hose, you’ll need a Presta adapter
(available at your bike shop) which screws on to the valve stem once you’ve freed up the valve. The adapter fits the end of the air hose
fitting. Close the valve after inflation. To let air out of a Presta valve, open up the valve stem lock nut and depress the valve stem.