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Ok, I have this:
[url= http://www.chainreactioncycles.com/Models.aspx?ModelID=50274 ]http://www.chainreactioncycles.com/Models.aspx?ModelID=50274[/url]
Always been schraeder, swapped to Presta, and no matter what I do, the air still comes out of the schraeder hole?? Nothing goes into the presta. I cant find a switch to transfer the air from one hole to the other or anything.
Please tell me I'm being stupid and it's a simple case of ___________.
Thanks!
You have unscrewed the nubbin on the presta valve, haven't you?
Haven't used that exact pump, but track pump heads often have a pressure valve which automatically switches the air to go to the hole with the most pressure resistance - i.e. the one you're pumping air into.
Try this:
Lift the pump handle.
Put your finger over the Presta hole.
Push gently down on the pump handle. This should switch the valve over to pump air through the Presta hole (you'll be able to tell because you'll feel the pressure on your finger and also the pump handle won't drop if you let it go).
Pump away!
Sometimes (really annoyingly!) the head will revert back to Schraeder as soon as you take the pressure off. Either try doing a very quick swap (without letting the pump handle drop) between your finger and the valve or fit the pump to the valve, then slip your finger under the tyre bead to block off the back of the valve to increase the pressure resistance.
It's supposed to be smart and sense which type is being used.
From one of the CRC reviews it suggests putting your thumb over the unused port so the pressure build up trips the seal.
neninja - that does the opposite of what you want to achieve. You need to block up the port you ARE using.
Why anyone uses Presta valves on an MTB has always been beyond me anyway. Fiddly unreliable little things that they are! 🙂
OK - I'm only passing on what an owner of this pump said in a review. I have no actual experience of it as my pump is of the simple twin head type.
Which ones are which? I never remember.
schraeder == car valves, presta == thin valves with the screw down lock
Ah, gotcha.
I've experienced this before (during an emergency bike shop stop) and even the bike shop owner couldn't get the pump to work. Ended up putting in a little bit of air with a mini pump, then the floor pump worked fine.
I had one of those heads, I junked it and bought a Topeak smart head, been using it in workshop conditions for 7 years and it's brilliant!
See its for tubeless so the whol 'build up pressure' bit is a bit of a no go.
Will look at a new pump!
I've a cheapish one and it won't pump unless the head is pointing "holes down" - no idea why
Solved!!
My colleague just so happened to have a brass fitting in his cars Plug-in Compressor that screws on the end of the presta to make it Schraeder 😀
Should come in handy for future use pumping tyres!
Will look at a new pump!
Just buy a new head. I got one of these for the office track pump
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£7.99 from crc
GSuperstart - works fine for tubeless, you only need to get it to "switch" once. Squishing the tyre so that valve outlet is hard up against it usually does the job.