4

I just bought a new mini pump (with a foot-stand and pressure gauge to get up to about 100psi), however, in order to get a good seal you have to screw the pump-head onto the valve.

The issue is, with the presta valves I run, when unscrewing the pump there's a long distance between the pumps seal breaking and being able to come free of the valve (letting it do its job), so if the tyre is up to 100/115psi it can often go back down to around 80 or 90 in the time I've unscrewed it.

Am I doing something wrong, or is it just a slightly awkward setup on the pump?

7
  • Is it a pump of good quality? I didn't see yet pumps with screw (except of the very cheap ones).
    – Alexander
    Aug 14 '15 at 10:16
  • 3
    Yes, it's unusual for a Presta chuck to be of the screw-on variety. Further, a Presta chuck does not need to have the pin in the middle to depress the pin of the valve. At the very least I suspect there's a piece inside the chuck that should be reversed when used with a Presta valve -- older "convertible" chucks had this requirement. Aug 14 '15 at 12:12
  • 3
    Lezyne makes some high quality screw-on pumps and I’ve never had any problem with them (except for screw-in valves coming lose which can be solved by installing with loctite). How do you know the tire is actually losing pressure and it’s not just escaping from the hose?
    – Michael
    Aug 14 '15 at 13:43
  • 1
    Yes, as @Michael suggests, when you remove any chuck from a tire valve after inflating, you will hear the hiss of air escaping from the hose. Of course, this shouldn't cause a loss of air pressure in the tire. Aug 14 '15 at 16:54
  • 1
    Could you tell the pump model? In Lezyne you have the air release "button" in the pump-head. Usually it is enough to just carefully unscrew the head.
    – mkpaa
    Oct 21 '15 at 23:20
1

There are a few possible issues. First of all remember to unscrew the pump head carefully, but that you are probably doing already.

Also in case you have Lezyne pump you should use the Air bleed button to release air before removing the pump head. For other models see the pump's manual.

You should also note the following:

1) The pumps pressure gauges are far from accurate. Try to check the tires pressure with your fingers (in case of road tires with your both thumbs next to each other)

2) The hissing sound you hear when releasing the pump head is not the tire deflating, but air released from the pump.

3) With presta valve (if they have replaceable core) you need to be extra careful not to unscrew the valve core when unscrewing the pump head. If that is a problem you can use glue with the valve core to prevent unscrewing it.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.