Thread: Presta Tubes
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Old 02-22-10, 01:17 PM
  #5  
Greenfieldja
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The plastic cap on schrader valves is important to keep debris out of the valve stem opening that could interfere with the spring. Schrader valves keep air in by means of a spring actuated valve. Presta valves keep air in by means of the air pressure pushing the valve closed, then the knurled stem of the valve is screwed down as extra insurance. Given the difference in design there is little chance for debris affecting the presta valve. Some cyclists/mechanics omit the cap on presta as taking it off is just one more step that they have to perform before a punctured tube can be replaced. Some might consider using the cap as additional assurance that the stem of the presta valve won't unscrew or to give the wheel that extra "finished look". To answer your question directly, it is perfectly fine to leave them off if you so choose.

-j
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