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Path: utzoo!linus!philabs!cmcl2!seismo!umcp-cs!gymble!lll-crg!brooks
From: brooks@lll-crg.ARPA (Eugene D. Brooks III)
Newsgroups: net.bicycle
Subject: Re: Presta Valves
Message-ID: <715@lll-crg.ARPA>
Date: Sat, 20-Jul-85 02:56:44 EDT
Article-I.D.: lll-crg.715
Posted: Sat Jul 20 02:56:44 1985
Date-Received: Sun, 21-Jul-85 03:47:57 EDT
References: <872@ihlpg.UUCP>
Distribution: net
Organization: Lawrence Livermore Labs, CRG group
Lines: 10

> I just re-wheeled my bike and went to 100-psi tires with presta valves. 
> I had no trouble inflating the tires, but I can't tell the tire pressure
> by looking at the gauge on my foot pump any more.  Presta valves operate
> by air pressure, so the valve doesn't stay open to move the gauge.
Get a good quality pump with a gauge and use good presta valves.  The pressure
in the tire will be the gauge pressure after the air has leaked into the tube.
The gauge needle jumps up to get the required opening pressure but as air flow
stops across the valve the pressures are nearly equal.
This gets ride of the rather large opening force error.  There is of course
some small error left but its only a pound or two and therefore not significant.