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Broken Presta Valve Top: Can I Ride Safely?

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Broken Presta Valve Top: Can I Ride Safely?

Old 06-16-07, 09:06 PM
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Jed19
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Broken Presta Valve Top: Can I Ride Safely?

I was pumping my tires for my ride tomorrow morning when the top of the presta valve sheared off. I really do not want to change the tube, as I have only one spare, which I plan to carry on my ride tomorrow.

The question is this: I have about 120PSI in the tire, and the air has not escaped. If I check the air in the tires tomorrow morning, and if the air has stayed intact, can I ride safely with the busted presta valve?

Thanks for all responses.

Regards,
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Old 06-16-07, 11:28 PM
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No takers?

Regards,
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Old 06-17-07, 12:15 AM
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Hi,

I've done this twice out of my last three events. The first time I did it, I figured it would be ok. After about 5-10 miles I noted my tire was slowly getting low. When I pulled into the rest stop after 25 miles, it needed changing. Granted I did not have a valve cap on it so that may have something to do with it.

Yesterday before the start of an organized ride, I broke one off again. This time I just changed it on the spot.

My advice, change it out.
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Old 06-17-07, 12:21 AM
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Should not be a problem. The nut is there only to prevent you from accidentally deflating your tire anyways.
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Old 06-17-07, 05:43 AM
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The nut will keep the valve from opening briefly if you hit a bump or pothole. Presta valves have no closing springs so the nut is needed to keep the valve closed under harsh conditions when air pressure alone isn't enough. You likely won't get a sudden flat but the tube could lose air incrementally.

Replace the broken one and buy or borrow a spare.
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Old 06-17-07, 11:29 AM
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Originally Posted by HillRider
The nut will keep the valve from opening briefly if you hit a bump or pothole. Presta valves have no closing springs so the nut is needed to keep the valve closed under harsh conditions when air pressure alone isn't enough. You likely won't get a sudden flat but the tube could lose air incrementally.

Replace the broken one and buy or borrow a spare.
Not exactly right. The presta valve is a check valve. Air can only go one way into the valve. It will remain closed unless you press on the stem which opens the valve. The only problem that LUCAS will have is when he goes to fill the tube. The valve will follow the Bernoulli principle. As soon as he burps the valve, pressure will flow around the valve and push it into the tube and all the air will come out. It's kind of cool.

But the tube is toast. Replace it next time you need to fill the tire.
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Old 06-17-07, 04:07 PM
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Thanks for all responses. I am reporting that I did ride on the busted tube this morning, and everything was fine. I rode 80miles.

I know I'll not be able to put air in the busted tube again, and my plan is to change it out before my next ride.

Regards,
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Old 06-17-07, 04:20 PM
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Originally Posted by cyccommute
Not exactly right. The presta valve is a check valve. Air can only go one way into the valve. It will remain closed unless you press on the stem which opens the valve.
Right enough. Presta valves are indeed check valves but the check feature can be overcome by finger pressure on the stem too. My point was that with no nut to keep the valve mechanically closed, a sharp jolt could pop the valve off of its seat and let some air escape. Apparently it didnt happed this time but I'd still not trust the tube to hold pressure while riding. They don't bother with the nut and screw shank for no reason.
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Old 06-17-07, 04:34 PM
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Originally Posted by HillRider
Right enough. Presta valves are indeed check valves but the check feature can be overcome by finger pressure on the stem too. My point was that with no nut to keep the valve mechanically closed, a sharp jolt could pop the valve off of its seat and let some air escape. Apparently it didnt happed this time but I'd still not trust the tube to hold pressure while riding. They don't bother with the nut and screw shank for no reason.
The valve doesn't have enough mass to open because of a jolt. Remember it's being held closed by the inner air pressure which puts a significant force on a rather light weight piece of metal. I agree that I wouldn't ride it.
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