Hello all, I have recently purchased a Gary Fisher. When I recieved the bike I found out that it is equiped with presto stems and I am very unfamiliar with these stems. Well the first 3 days it was all nice no problems at all and then when I was getting my bike ready for a Saturday morning trail ride I found my tires flat. Now panicing I quickly assumed that I had thorns in my tire from the night before so I looked. I did pull out thorns but none of them were long enough to get through my thorn resistant tubes and the liners between the tubes and the tire. I in turn tried to fill up the tires with the adapter that I recived with the bike and you know I was blown away when the air came right back out through th base of the stem. When I returned home from the service station I pulled the tire up just barely enough to see that there was a fitting for the valve to connect to the tube????????????? What is this mess? How can I prvent that from happening again? Now I am bummed cause the cycle shop is closed until monday and I have no bike for my morning ride. Any suggestions?????????
Mountain Bikes · Public discussion
Presto valves !!!!!
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- Mountain Bikes
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- 20 August 2005
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- 13 September 2005
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- Az_eagle
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Az_eagle said:
Hello all, I have recently purchased a Gary Fisher. When I recieved the bike I found out that it is equiped with presto stems and I am very unfamiliar with these stems.
The "Presta" valves (a.k.a. "French" valve) are a thin valve so the rim people don't need to drill as big a hole in the rim for the valve, so the rim is stronger. At least that's what I read somewhere 🙂Anyway. They work not with a spring-loaded valve (like car, aka "Schrader" valves), but with a little nut you manually have to screw and unscrew.
To inflate one of the Presta valve tubes, you need to unscrew this little nut at the top, give the valve a bit of a tap to get the valve used to opening, and then pump it up (with the adapter if need be)
Then once you're done, screw that little nut back down again to prevent the air from escaping too easily (it won't whoosh out if it's open, but screwing the nut locks it down to stop the air from 'burping' out)
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rek said:
The "Presta" valves (a.k.a. "French" valve) are a thin valve so the rim people don't need to drill as big a hole in the rim for the valve, so the rim is stronger. At least that's what I read somewhere 🙂
Presta vavles are also intended for higher pressures, and better pressure retention. Also good if you need to let your tubes down regularly (tyre changes etc).All I will add is that when inflating them, back the nut off all of the way, and make sure you do bleed a little air out. You may have to pump quite hard before you get any air goin into your tyres (because you have to force air against the existing pressure in the tube). You will get a little sharp hiss when you take the pump off, this is just the pressure in the pump line escaping, not fom the tyre itself....
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I would recommend getting a stock of spare tubes in.
They are cheap and it neatly gets round all these types of problem.
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