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Old 12-07-07, 01:18 AM   #1
Sportsman9
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I want to pump ... you up!

Help please, I'm losing a lot of air in my tires every time I remove the pump from the valve (well, almost every time).

I have Schraeder valves and a Specialized floor pump. The pump has a long hose, and at the end there's a lever which can be set "up" or "down".

Please correct me if I'm doing anything wrong:

* Lever down. Stick hose onto valve and press down a bit (how much?). (Of course I'm not a total noob, I did remove the valve cap first!)

* Move lever up. Start pumping until meter reads 80.

* Snap lever down, and try to instantly remove the hose from the valve. Here there usually is a struggle, and I'm not sure how hard to yank/twist. I hear hissing and ...

* By the time it's off, the tires usually have the same amount of air they started with.
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Old 12-07-07, 01:44 AM   #2
Siu Blue Wind
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Over pump. That way when you lose air, it will go to the desired pressure.
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Old 12-07-07, 03:23 AM   #3
CommuterRun
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Are you sure the air you're hearing escape is coming from the tire and not the hose on the pump? Are you checking the tire pressure with a gauge, other than the one on the pump where the air has to fill the hose before getting to the gauge?
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Old 12-07-07, 06:50 AM   #4
lechat
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i dab a little vasoline on the valve. pump nozzle comes off easier and rubber doesn't get chewed up.
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Old 12-07-07, 08:59 AM   #5
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Quote:
Originally Posted by Sportsman9 View Post
Help please, I'm losing a lot of air in my tires every time I remove the pump from the valve (well, almost every time).

I have Schraeder valves and a Specialized floor pump. The pump has a long hose, and at the end there's a lever which can be set "up" or "down".

Please correct me if I'm doing anything wrong:

* Lever down. Stick hose onto valve and press down a bit (how much?). (Of course I'm not a total noob, I did remove the valve cap first!)

* Move lever up. Start pumping until meter reads 80.

* Snap lever down, and try to instantly remove the hose from the valve. Here there usually is a struggle, and I'm not sure how hard to yank/twist. I hear hissing and ...

* By the time it's off, the tires usually have the same amount of air they started with.
You are not doing anything wrong other then worrying about something you shouldn't. The valves in a tube are check valves. That means that air goes in but the valve closes to keep the air from coming back out. On a presta valve, the internal air pressure keeps the valve closed while on a schrader valve there is a spring that closes the valve once you release the thumblock. There is a little nipple inside the head of pump for schrader valves that depresses the valve to keep it open as you pump. Once you flip the thumblock, the tube valve shuts and the air stays inside the valve.

The hissing and whoosh of air you here when you take the pump head off is the air inside the pump hose. Don't worry about it.

The one caveat is that sometimes the nipple on the schrader pumphead can remain in contact with the valve and let some pressure out. Try not to rock the head taking if off but schrader pump heads are usually pretty loose.

Presta heads are very tight but there isn't anything in the head to push down on the valve so you shouldn't lose any air. Try to pull the head straight up and off and resist twisting it from side to side. this can bend the stem.
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Old 12-07-07, 07:35 PM   #6
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Originally Posted by CommuterRun View Post
Are you sure the air you're hearing escape is coming from the tire and not the hose on the pump? Are you checking the tire pressure with a gauge, other than the one on the pump where the air has to fill the hose before getting to the gauge?
I'm with this guy--I sweated that for years until a mechanic told me it was just air escaping from the hose. A three-foot length of air hose at 100psi or whatever will take a second or so to equalize, and you may be hearing that.
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