From: tssmith@netcom.com (Tim Smith)
Subject: Re: using presta tubes with a Schraeder wheel
Date: Wed, 19 Aug 92 01:29:01 GMT
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Keywords: presta to schraeder

In article <rlewis.714151861@muskwa.ucs.ualberta.ca> rlewis@muskwa.ucs.ualberta.ca (Robert Lewis) writes:
> gcarter!gcarter (George Carter) writes:
> >4. Schraeder replacement tubes are available on the road in any town
> >   large enough to have a drug or grocery store.  Presta generally are
> >   less available, though any bike shop would have them.
> 
>                                               If you were going on an
> extended tour in areas poorly served by bike shops (e.g., South America,
> Africa though I don't know what the common valve types are there) I 
> would consider using Presta tubes (easier to fill fewer slow valve
> leaks) and Schraeder valve rims just in case you were really stuck 
> (I've filled tires to 130 lbs./sq inch with Presta tubes in Schraeder 
> rims).

It's easy to drill out the valve stem hole in a Presta rim to take a
Schrader valve stem.  You _should_ be able to find a drill in any
village repair shop anywhere in the world, so I wouldn't use a
Schrader rim just for this possibility.  Lacking a drill, you can file
the hole to size with a small round file (I had to do this once in a
small town in ... Montana).

> >5. Presta protective caps are lost due to vibration far more easily.
> 
> But protective caps aren't needed by either valve (though I've never
> lost either sort of valve other than by leaving it somewhere).

The caps are there for two reasons.  The main one is to keep the
valve mechanism from being clogged with road grit. If you don't ride
in bad weather you might not need them, but then they don't really
weigh much, do they?  Also, a Schrader valve core remover/tightener
built into the valve cap is very handy.  (Why are these no longer
available?)

For Schrader valves on some high-speed vehicles, such as motorcycles,
where the valve stem is mounted normal to the plane of rotation of
the wheel, they (BMW, for example) claim that centrifugal force can
cause a Schrader valve to open at high speeds (100+ mph).  So these
bikes have steel valve caps with small rubber seals, to provide extra
protection if this happens.  Given the low mass of the valve plunger,
I suspect that this would happen only if the spring is weak or
broken, and perhaps the tire is underinflated.

> >6. Schraeder valve leak detection requires only saliva, which is 
> >   far more convenient on the road than the cup of water Presta 
> >   valves require.
> 
> Do Presta valves ever leak (as opposed to outright breaking)?  I've
> never experienced leaking Presta valves, though I have had leaking
> Schraeder valves.

Presta: me neither.  With Schrader valves, you need the valve core
wrench, or a small pair of needle-nose pliers, to stop the leaks,
which are not uncommon.
 
> Robert M. Lewis

--Tim (tssmith@netcom.com)

PS:  John Forester (Effective Cycling) has recommended cutting the
spring from a Schrader valve core, then removing the pin from the
pump connecter.  I've never tried it; does it make Schrader-valved
tires easier to pump?  I can see where it would prevent the problem
of air loss as you remove the pump, common with older non-Zefal type
pumps, especially those evil contraptions with hoses and screw-on
connectors that used to be common (RIP).



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