The Duckmeister wrote:Some track pumps are just plain touchy on Presta valves. If I get one that won't stay sealed properly, I rest a thumb over the tyre, grab the head of the pump with the fingers & squeeze so I pull the pump head onto the valve firmly & pump one-handed. Yes, it's bloody hard work to get that last 20 or so PSI, but sometimes it's the only way to get the pump to stay on.
You don't happen to have one valve with a fully threaded stem and one unthreaded (bar the thread at the tip for the cap) do you? Unthreaded valves do allow the pump to slip off enough to break the seal as the pressure gets up. The trade-off is that threaded valves rip the rubber in the pump head apart faster.
victor wrote:OK, thanks . I'll continue with the Presta valves for now, because I don't want to make any hasty decisions, since drilling the holes out is irreversible. Or perhaps I need to consider another floor pump? I currently have a "Wrench Force" pump.
May not necessarily be the o-ring wearing if it hasn't seen much use on Presta valves yet. It could be the cam in the thumblock that causes the rubber to squeeze onto the valve. Quite probable if the pump has had a lot of use.Riding Every Day wrote:Duck is right Victor. It'll be the o-ring in the pump head losing grip as you increase the pressure in the line.
rjk wrote:i have a giyo gf12 i got from cycle science in mitcham after trying theirs one day as my bike was in for a service.
it was so easy to use and it has an automatic head that is good for presta and schraeder.
I haf a topeak that failed and even a replacement head failed 3 months later....
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