nz6666

Ok I am new and new to presta valve. I find it too delicate/fiddly compared with schrader. This is probably due to my inexperience/knowledge. Anyway the tube I am looking for (23x406) is presta only. I was using a foot pump with a schrader to presta converter coming with the pump. I released the top little valve on the presta, screwed the converter onto the valve body, then connected the pump to the converter. Ok when I done the pumping, I detached the pump from the converter, unscrewed the converter. But doing so actually unscrewed the core of the presta valve out while the converter still screwed on the core! I hope I took a picture of the core so you would know better what I mean. I had to find a pliers to get the core out then screwed it back to the valve.

I found the only way to work is not to screw the converter on the valve, but put it on the valve, apply a little pressure and make sure the converter align with the valve, then have another friend/family member doing the actually pumping as I have to use both hands to hold the converter in place. Even so, it's very easy to hear the leaking from the where converter attaching the valve as it's a very loose connecting.

Suggestions?

JohnDThompson 

You'd probably have better luck with a pump head designed to be used on a Presta valve; you simply push it straight off the stem rather than un-screwing it. Those adapters work best when attached to a compressor, not a pump.

Wilfred Laurier

The mistakes many people make is screwing the adaptor too far onto the valve stem (stop tightening when the rubber gasket is firmly against the 'shoulder' where the diameter of the valve stem increases), and unscrewing the presta lock nut too far (generally you only need to unscrew the valve about half way - unscrewing it too much brings the little nut too far into the adapter and can mess things up.

Consider getting a good bicycle floor pump - most of them have heads that are designed to work with presta valves so no adapter is necessary.

dsbrantjr

Don't forget to "burp" the valve open after you loosen the cap nut, in case it is a little sticky.

Andrew R Stewart 

If the valve core is tightened properly it won't loosen when the adaptor is being dealt with. There is an adaptor style with a large rubber grommet inside that doesn't thread on (SKS is a popular one) but the little brass and AL ones really want to be threaded on, just make sure the core is tight first. It helps to tap open the presta valve's top nut before inflation, they can get stuck shut. One can convert their pump to a head with dual presta/schrader fittings and avoid the adaptor completely. If you ever were to use a hand pump (while out on the road/trail) you'd understand one reason for the presta valve and it's "only open valve when air is entering the valve" design. Andy.

2manybikes

You may have bent the threaded rod that the presta valve has in it. That may be hitting the adapter when you turn it. I have never tried to bend one back. I used a new tube once when I did that.

nz6666

Thanks for the replies. I may have screwed the adaptor too far onto the valve. And also I am considering to get a descent dual head pump.

tomacropod

Just do the valve core up tighter.

davidad

Ditto. Use small pliers to make sure the core is tight. I have seen them come off by hand.

fietsbob

Don't really need removable core P/V stems . one less thing to mess Up.

bikepro

If you have a pump or adapter that screws on and have removable cores, you need to tighten the cores. As long as you keep them tight, they will not back out when you unscrew the adapter/pump.