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Bicycle Tubes: Presta Valves
Bike Tire Tube Stems

A bike tire tube stem is the small metal valve on typical bicycle tubes that allows you to attach a pump and fill up your tire with air. The tube stem typically comes in two different designs, each with its own set of advantages.

Presta Bicycle Tube Valves:
Presta Bike Tire Tube StemThis is the slimmer newer redesign of the tube stem. A Presta Valve requires a smaller hole in the bike rim causing less impact on the overall strength of the rim. The older Schreader valves with their larger stem diameters required manufacturer to stay with wider rims to maintain stiffness and strength around the port hole. A presta bicycle tube valve solves that problem offering greater flexibility in design.

For this reason presta valves are typically used on higher end mountain bike rims and on all slim line road bikes. For competitive bikers looking for every edge, these valves are also much more aerodynamic and are less likely to unbalance the wheel.

Some presta bike tube valves do have a removable valve core, which is necessary if you would like to use tire sealant product and fill it on your own. The word on the street though is that these double screw-in valves have a bad habit of coming loose and require a set of pliers for onroad repairs. Thus I'd avoid the whole story by buying prefilled self sealing tubes or stay with the regular ones and use tire liners for puncture protection.

presta  valve adapterTo fill a tube via a presta valve, you must use an adapter in order to use a common gas bar pump. This adapter can be left on the rim if you are likely to forget it at home and don't usually bring a pump with you on your rides. But this may kind of counteract some of the advantages of using a presta valve by adding more weight to the outer circumference of the wheel and increase the power needed to initial accerleration.

Presta valves do require less effort during inflation because there is no spring holding the valve closed as with Schraeder valves. They are better at holding the higher pressures found in road tires, and less prone to leaking.

It is important to remember that the types of bike tire tube stem can affect robustness. A presta valve is much more fragile than a Schraeder valve and therefore extreme care must be taken during filling so that it does not get snapped off. Carrying a replacement tube is essential. It is impossible to fix a tube stem, and no fun if you have to push your bike five miles out of the bush.

More Articles of Interest:
Bicycle Tubes and Their Design

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copyright Jan. 2007