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presta valve screws out
Another day, another surprise. I found out that the presta valve on one of my
tubes screws out. In fact, it screws out and the tube loses pressure appr. one out of ten times when I screw of the little plastic valve cap from it. I never knew that those cores can be screwed out and it appears that on all but one of my tubes it can't be screwed out, and are in fact not even separate pieces but are part of the valve stem. Let me try to specify. It's not the "core" what screws out but the thing which holds the core and which itself is screwed into the valve stem. So when this thingie can be screwed out, is this a "lower" or "higher" quality indicator. Also, how can I screw it in so it would never ever screw out again, I tried to wrap a rubber piece around it and then use a wise grip plier but I am not sure it worked. Thanks, Paul |
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"Paul Nevai" wrote in message ... Another day, another surprise. I found out that the presta valve on one of my tubes screws out. In fact, it screws out and the tube loses pressure appr. one out of ten times when I screw of the little plastic valve cap from it. I never knew that those cores can be screwed out and it appears that on all but one of my tubes it can't be screwed out, and are in fact not even separate pieces but are part of the valve stem. Let me try to specify. It's not the "core" what screws out but the thing which holds the core and which itself is screwed into the valve stem. So when this thingie can be screwed out, is this a "lower" or "higher" quality indicator. Also, how can I screw it in so it would never ever screw out again, I tried to wrap a rubber piece around it and then use a wise grip plier but I am not sure it worked. Thanks, Paul I don't have any answers for you, but I share your frustration. I don't know why some are made this way and some aren't. I suspect Jobst will chime in and clarify this. Anyway, bonehead me left on a long ride a few weeks back and had only one CO2 cartridge in my seat bag. I got a flat. I changed it out. My wheels have deepish, semi-aero rims and I have to use a valve extender to pump them up. So I've used my last CO2 cartridge to fill the repaired tire and I go to remove the valve extender. The core of the new tube unscrews with the valve extender and there I am ... stranded. I live in a very rural area. I had a very long walk to get to where I had a cell phone signal to be able to call home. I spent a lot of that time wondering what possible reason there could be for the core of a valve to unscrew like that. Never came up with one. Bob C. |
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"Paul Nevai" wrote ... Another day, another surprise. I found out that the presta valve on one of my tubes screws out. In fact, it screws out and the tube loses pressure appr. one out of ten times when I screw of the little plastic valve cap from it. I never knew that those cores can be screwed out and it appears that on all but one of my tubes it can't be screwed out, and are in fact not even separate pieces but are part of the valve stem. I discovered the same thing about a spare tube I was installing the other day. The tube had an extra long valve stem to fit an aero or semi-aero rim. I suspect that the removable valve lets the manufacturer install valves in stems of varying lengths, according to consumer demand. So when this thingie can be screwed out, is this a "lower" or "higher" quality indicator. Mine seems to be about the same quality as the valves on the other tubes I buy. Also, how can I screw it in so it would never ever screw out again, I tried to wrap a rubber piece around it and then use a wise grip plier but I am not sure it worked. I suspect that this would distort the valve or strip the threads, making the whole thing useless. I got mine as tight as I could with my fingers, left it at that, and made a note not to buy that brand of tube again. -- mark |
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I believe the reason is, if you bend the valve, you can replace it. As for
tubulars, you can unscrew the valve, install an extension, and then screw the valve into the extension piece. It makes for a far far better seal then using the valve extenders that screw on over the valve fitting. Its a great feature. David |
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wrote in message ... On 12 Sep 2004 13:44:43 GMT, (Paul Nevai) wrote: Another day, another surprise. I found out that the presta valve on one of my tubes screws out. In fact, it screws out and the tube loses pressure appr. one out of ten times when I screw of the little plastic valve cap from it. I never knew that those cores can be screwed out and it appears that on all but one of my tubes it can't be screwed out, and are in fact not even separate pieces but are part of the valve stem. Let me try to specify. It's not the "core" what screws out but the thing which holds the core and which itself is screwed into the valve stem. So when this thingie can be screwed out, is this a "lower" or "higher" quality indicator. Also, how can I screw it in so it would never ever screw out again, I tried to wrap a rubber piece around it and then use a wise grip plier but I am not sure it worked. Thanks, Paul Dear Paul, Sealant tubes use this design to allow pumping goo into the tube. If you're screwing a plastic cap onto a Presta valve so hard that it unscrews a metal fitting, you may be using considerablly more force than necessary. I'm not recommending a torque wrench for valve caps, but using two fingers and a lighter grip may help. Carl Fogel Carl, If you've ever used a valve extender, you know that you sometimes have to screw them on pretty tightly to avoid having more of the air you pump in exit via the threads instead of going into the tube. It can be a real trick to screw them on tight enough for inflation, but loose enough that they can be removed without coring the valve. FYI, Bob C. |
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On Sun, 12 Sep 2004 13:44:10 -0400, "psycholist"
wrote: wrote in message .. . On 12 Sep 2004 13:44:43 GMT, (Paul Nevai) wrote: Another day, another surprise. I found out that the presta valve on one of my tubes screws out. In fact, it screws out and the tube loses pressure appr. one out of ten times when I screw of the little plastic valve cap from it. I never knew that those cores can be screwed out and it appears that on all but one of my tubes it can't be screwed out, and are in fact not even separate pieces but are part of the valve stem. Let me try to specify. It's not the "core" what screws out but the thing which holds the core and which itself is screwed into the valve stem. So when this thingie can be screwed out, is this a "lower" or "higher" quality indicator. Also, how can I screw it in so it would never ever screw out again, I tried to wrap a rubber piece around it and then use a wise grip plier but I am not sure it worked. Thanks, Paul Dear Paul, Sealant tubes use this design to allow pumping goo into the tube. If you're screwing a plastic cap onto a Presta valve so hard that it unscrews a metal fitting, you may be using considerablly more force than necessary. I'm not recommending a torque wrench for valve caps, but using two fingers and a lighter grip may help. Carl Fogel Carl, If you've ever used a valve extender, you know that you sometimes have to screw them on pretty tightly to avoid having more of the air you pump in exit via the threads instead of going into the tube. It can be a real trick to screw them on tight enough for inflation, but loose enough that they can be removed without coring the valve. FYI, Bob C. Dear Bob, True, but the original post specifically complains about plastic valve caps, not extenders. As for valve extenders, I found them so annoying that I switched to long valve stems after fooling around with teflon tape to seal the threads. Another problem is that the extender is just a hollow shell that fits down over the real Presta valve, whose lock-nut must be left unscrewed, leaving nothing but air-pressure to seal the valve. In addition to the obvious problem of losing air-pressure without a lock-nut, the extender makes it hard to break a stuck valve free. This can cause two problems. First, you can't pump the tube any further if the valve sticks on a mostly-filled tube. Second, you can't let the air out to collapse a slow-leak flat to remove the tire. So you have to remove and replace the extender, an awkward job, or else carry something to poke down into it to free the hidden Presta valve. In general, most small adaptors, extenders, and adjustable devices fail to work as well as the real things whose specific purpose they are meant to imitate. Carl Fogel |
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wrote in message ... ..... As for valve extenders, I found them so annoying that I switched to long valve stems after fooling around with teflon tape to seal the threads. Another problem is that the extender is just a hollow shell that fits down over the real Presta valve, whose lock-nut must be left unscrewed, leaving nothing but air-pressure to seal the valve. In addition to the obvious problem of losing air-pressure without a lock-nut, the extender makes it hard to break a stuck valve free. This can cause two problems. First, you can't pump the tube any further if the valve sticks on a mostly-filled tube. Second, you can't let the air out to collapse a slow-leak flat to remove the tire. So you have to remove and replace the extender, an awkward job, or else carry something to poke down into it to free the hidden Presta valve. In general, most small adaptors, extenders, and adjustable devices fail to work as well as the real things whose specific purpose they are meant to imitate. Carl Fogel If you use an extender such as: http://www.worldclasscycles.com/valv...nsion_tube.htm you'll find that they have a valve control that allows you to open and close the valve. The metal extenders do need an O-ring or Teflon tape for a good seal on the valve, but plastic versions of this type of extender will seal as is. Chuck Davis |
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On Sun, 12 Sep 2004 13:44:10 -0400, "psycholist"
wrote: If you've ever used a valve extender, you know that you sometimes have to screw them on pretty tightly to avoid having more of the air you pump in exit via the threads instead of going into the tube. It can be a real trick to screw them on tight enough for inflation, but loose enough that they can be removed without coring the valve. If you put some teflon tape on the valve stem, the extenders work fine. You can also put a piece of teflon into your patch kit. |
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