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I have had a generic floor pump from an online bike catalog company for years, and have filled many Schrader valve tires with it without any problems. I have recently started to use Presta valve tires. When I try and pump air into a Presta valve tire, the air doesn't seem to go into the tire. It takes me several trys at reseating the pump to get it to work, and every time it does work, there is a distinctive "pop" sound.
How do I get it to work every time?

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It isn't per chance a Hurricane floor pump? I have the same exact issue, but have never been bothered enough to find a solution. –  WTHarper Aug 27 '12 at 3:26
    
Yes, it is a Hurricane floor pump. –  WireGuy Aug 27 '12 at 21:33
    
Weird. Maybe they're just not great pumps? I've never had any issues with my other pumps. –  WTHarper Aug 28 '12 at 2:57

3 Answers 3

up vote 13 down vote accepted

What I find helps, is: tap the valve post a bit to let out a small blast of air (after loosening the captive nut all the way, of course). That helps unstick things and lowers the pressure inside a bit to make it easier to start pumping air in. Just takes a quick tap. If you don't do that, you may need to pump slightly past the pressure of the tire to actually start pumping air in.

A Schrader valve is a spring-loaded valve that the pump head opens up by pushing down on a pin. That means that once the head is engaged, pressure is equalized between the pump hose and the inner tube of the tire. When you engage the head, some air comes out of the tube into the pump head and hose, and when you work the pump, you're immediately pumping air into the tube/tire.

A Presta valve doesn't have a spring. The valve is kept closed with air pressure, and the captive nut helps ensure nothing bumps the valve open. The pump head generally does not press down to force the valve open, and instead the valve is opened by increasing the pressure in the hose past the pressure inside the tube/tire. You generally have to pump until the pressure in the pump/hose/head matches what's in the tube before any air actually flows into the tube/tire, and sometimes a bit past that.

I suspect that the "pop" you're hearing is when external (hose) pressure overcomes the Presta valve, it opens up, and pressure equalizes suddenly between the pump hose and the tube.

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If it's a loud pop, keep an eye on the pressure gauge...you can overload the hose on the pump while trying to equalize...especially if the presta is stuck for some reason. –  Ken Hiatt Aug 27 '12 at 5:51

That's just how it works with Presta valves. When you attach the pump head to the valve, it does not open the valve mechanically. The valve remains closed. In order to open the valve you have to start pumping the air. That external air pressure that you create with the pump (i.e. pressure in the pump hose) has to force the valve open. The moment it opens is when it makes that "pop" (or "tick") sound. Once it opens, it stays open until you disconnect the pump.

How much pressure it will take to open the valve depends on how "sticky" your Presta valve is and on how much pressure you already have in your tire. To make it easier, you should tap the valve head a few times with your finger before attaching the pump and, preferably, drain some air to reduce the inner pressure in the tube.

Some pump heads have a pin in them, which is there specifically to mechanically open the Presta valve when you attach the head (some Lezyne heads?). Such pump heads usually don't exhibit this "sticky valve" issue. However, such pump heads are relatively rare. A typical pump head for Presta relies on air pressure to open the valve, as I described above.

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Yep, first, of course, unscrew the little knob all the way. Then, before installing the pump chuck, press the knob in briefly to let out of burst of air and assure that the valve is not stuck closed.

Also, when tightening the little knob tighten it only just barely finger tight -- don't try to get it super-tight. If you overtighten the valve you distort the rubber seal in the valve and shorten its life (in addition to making it more likely to stick).

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