Valves

[TonySmith]

Pumping up all the bike tyres at the weekend got me wondering why we have two different types? My wife's old MTB, my brompton and my daughters (14") all use schraeder but my 26" Thorn uses Presta. My rear wheel is the original, drilled for schraeder with a grommet to convert to presta. I used to think it was something to do with presta valves being able to take higher pressures but the Brompton tyres run at 100psi.
 Does anyone know if one type has any technical advantage over the other?

[tynevalleycommuter]

I think you are correct that presta valves are generally intended for higher pressure use - I run my road tyres at around 120 psi on presta valves, and you cannot get the narrower road inner tubes (as far as I am aware) with schraeder valves, which obviously need a larger hole in the rim. For 26" touring wheels you have the choice of either type, but for most other wheels it is probably a case of one or the other. Narrower 26" tubes for higher pressure tyres tend to have presta valves whereas bigger tubes (for running at lower pressures) will almost always have schraeder, but there is some overlap.


The main technical difference is that the cores of schraeder valves are (or used to be) replaceable by unscrewing the valve core out of the stem. Some old car dust caps and tyre pressure gauges used to have a small forked tool on/in the end to engage around the core to unscrew them. Not sure if MTB type tubes are the same, and it's possible that the valve part is more reliable these days than older car ones used to be, rendering the need to make the cores replaceable somewhat redundant. I'm not sure if you could buy a spare valve core these days even if you wanted to!

There are also the old Woods type valves; although I have a few bits in one of my toolboxes I haven't used one for at least 30 years!

As usual Sheldon Brown is a mine of information on such things with links to all 3 types from this page:- http://www.sheldonbrown.com/tyres.html

[flanderflop]

The main reason that I like the presta better is that when I change a tire (because I want a different tire, not because of a flat) it is easier to let the air out.

Other advantages.  Smaller drilling in the rim is better for narrow rims and the valve won't collect dirt if you take the cap off.

[tom w]

Presta pump more easily, to higher pressure, being designed for intermittent pressure (like a bike pump!), Schraeder apparently designed for constant flow inflation, like an airhose. Most Schraeder valve cores are not interchangeable, as different brands seem to use marginally different shapes and lengths, however valves fail at a minute fraction of the rate that tubes do. I took the cores out of Schraeder valves before throwing dead tubes away, but gave up having never used one.

For expedition touring, using Schraeder-drilled rims with Presta-valved tubes, together with grommet to support the narrower valve makes sense - easy pumping, but you can use cheap, nasty Schraeder- or even Woods-valved tubes in the back of beyond, when your spares can't take more patching, are torn etc.

[jonathan]

Interesting points you make tom w. I tend to use all Schraeder valves these days after having seen too many bent and buggered presta's. I also usually use large volume low pressure tyres and tubes. It seems pretty hard to stuff a schraeder.

Should you happen to get caught somewhere with out a pump you can always get some air from a servo airline with a schraeder valve.