Thursday, December 26, 2013

Presta Valve Follies

A few days ago while putting air in a road bike tire before taking off to work, I managed to remove the pump head such that it snapped the front tire's Presta valve stem off. This is the second or third time I have had this happen - admittedly over something like 15 years, so not exactly an everyday thing. Still, it is annoying since I typically put air in the tires right before taking off. In this case, since the broken valve didn't let any air out but simply meant I could no longer put air in, I decided to ride to work and back before dealing with it - that is, replacing the tube with a new one with a working valve. So I wasn't slowed down on departure much.

The Presta valve - the part that should insert into the pump and open the tube to receive air snapped off

This situation was preceded by bending the stem at some point, which apparently creates a weak point. Then I suppose when I loosen and tighten the lock nut every time I put air in the tire, it puts some stress on the bend, or something like that. Then at some point as I pull the pump head off, it is at such an angle that the stem snaps.

Inner tubes with working Presta valves

The replacement tube I will use is at left - I an using the tube that was in my bicycle tool bag, which was in a bag with talcum powder so it will move around easily in the tire and not get trapped between the rim and the tire during installation. I will coat the newer tube at right in talcum and put it in the bike tool bag.

Schrader valve patent from 1892

Apparently the Presta valve is more suitable for high pressure situations than the older Schrader valve - or at least I think the Schrader valve design is older. In Google's patent database the Schrader valve carries the Schrader name from its being patented in the U.S. in 1892. The Presta valve is a little more mysterious.

Is this the earliest Presta valve-like patent? from 1897

According the Wikipedia article on Presta valves some Presta valves now have removable cores which is not something I had realized was even possible. It says, "removable core Presta valves have become more common" - perhaps, but not on the low cost (i.e., cheap) tubes I buy. (Schrader valves all have removable core valves - a slow leak with a tire with a Schrader valve can simply be that the valve is not tightly installed. A very useful thing is a Schrader valve cap made of metal that has a built-in valve core remover/tightener.)

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