Bicycle Mechanics - Valve question

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TJohn
05-27-08, 07:00 AM
Took my bike to my LBS for a check up and while I was there I had them install some new tires. Once I got home I wanted to adjust the pressure and noticed that they gave me a different tube on the rear with what looks to be a schrader valve but it has a screw top like a presta?? And I can't seem to work it right, using my pump, I pump 3 times and it says 120 then continues to drop. I can't seem to be able to read what the pressure is. I don't like it :mad: Does anyone know what kind of valve it is and am I doing something wrong?

CACycling
05-27-08, 12:00 PM
I don't believe there is a third option for valves on tubes so I am assuming it is a presta. It sounds like you are not seating the pump far enough on the valve to open it up. Make sure the lock nut is fully unscrewed and that you have the pump fully down on the valve.
04jtb
05-27-08, 12:01 PM
maybe a presta-schraeder adaptor on there? what I use when pumping the tyres, just i take it off after

TJohn
05-27-08, 12:40 PM
I thought I unscrewed it until is stopped, but if it's an adapter it should come right off without any force correct?
04jtb
05-27-08, 12:41 PM
Yeah, it may not (probably isn't) an adaptor, it was just a thought
TJohn
05-27-08, 01:14 PM
No, it must be an adapter since there are only 2 kinds of valves. My front is a presta. I'll check it when I get home.
Camilo
05-27-08, 03:46 PM
Sometimes with presta valves it helps to let a little air out before you put the pump on it. On some of my tubes, this seems to help the pump open the valve when you start pumping.
maddmaxx
05-27-08, 04:03 PM
I don't believe there is a third option for valves on tubes so I am assuming it is a presta. It sounds like you are not seating the pump far enough on the valve to open it up. Make sure the lock nut is fully unscrewed and that you have the pump fully down on the valve.

It is not a good idea to press the pump down far enough to push on the rod in a presta valve. This is how the valve gets damaged and bent. Air pressure greater in the pump than in the tube will cause the presta valve to open. However, as mentioned in another post above, a quick tap with the finger to burp out some air before hooking up the pumb will unstick frozen valves.
JanMM
05-27-08, 05:12 PM
Was it a Dunlop valve? Never seen one but they exist.
http://en.wikipedia.org/wiki/Image:Dunlop_valve.jpg
TJohn
05-27-08, 05:17 PM
Yeah, I'm a real dumb@@@, it was an adapter over my presta :) All is well now.