Assessments - 1, GPA: 4
(
)
)
|
Facilidade de uso
Tire pressure is given either as maximum pressure or as a pressure range. How a tire performs under different terrain or weather con di tions depends largely on tire pres sure. Inflating the tire to near its max i mum rec om mend ed 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 rec om mend ed 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 con di tions 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, or damage the wheel rim, making the wheel unsafe. ! CAUTION: Pencil type automotive tire gauges 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 Section 1.C 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 uni di rec tion al 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 uni di rec tion al tires, be sure that they are mounted to rotate in the correct direction. 20 2. Tire Valves There are primarily two kinds of bicycle tube valves: 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 valve (fig. 17) is like the valve on a car tire. To inflate a Schraeder valve tube, remove the valve cap and clamp the pump head 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 ap pro pri ate object. The Presta valve (fig. 18) has a narrower di am e ter 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 Schraeder pump fitting, you need a Presta adapt er (available at your bike shop) which screws on to the valve stem once you’ve freed up the valve. The adapter fits into the Schraeder pump 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. ! WARNING: Patching a tube is an emergency repair. If you do not apply the patch correctly or apply several patches, the tube can fail, resulting in possible tube failure, which could cause you to loose control and fall. Replace a patched tube as soon as possible. 5. Service ! WARNING: Technological advances have made bicycles and bicycle components more complex, and the pace of innovation is increasing. It is impossible for this manual to provide all the information required to properly repair and/or maintain your bicycle. In order to help minimize the chances of an accident and possible injury, it is critical that you have any repair or maintenance which is not spe cifically described in this manual performed by your dealer. Equally important is that your individual maintenance requirements will be determined by everything from your riding style to geographic location. Consult your dealer for help in determining your maintenance requirements. ! WARNING: Many bicycle service and repair tasks require special knowledge and tools. Do not begin any adjustments or service on your bicycle until you have learned from your dealer how to properly complete them. Improper adjustment or service may result in dam age to the bicycle or in an accident which can cause serious injury or death. If you want to learn to do major service and repair work on your bike, you have three options: 1. Ask your dealer for copies of the manufacturer’s installation and service instructions for the components on your bike, or contact the component manufacturer. 2. Ask your dealer to recommend a book on bicycle repair. 3. Ask your dealer about the availability of bicycle repair courses in your area. Regardless of which option you select, we rec om mend that you ask your dealer to check the quality of your work the 21 first time you work on something and be fore you ride the bike, just to make sure that you did everything correctly. Since that will require the time of a mechanic, there may be a modest charge for this ser vice. just to make sure that you did everything ...