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Someone in my bike club suggested when you ride, loosen the nut all the way on your presta valve and when you blow up the tire, tighted the nut. The reasoning for this is if the nut is loose when you are riding and you get a flat, sometimes the tube will move inside the rim/tire. If the nut is loose, it will slip which is good. If the nut is tight, when you have a flat and the tube moves, it puts stress on the rubber around the valve and it could rip either then or later. When you are putting air in the tube, tighten the nut to prevent the valve from moving and thus ripping the valve out of the tube.

He suggested this as when I had a flat yesterday and I put in a new Michelin tube with a smooth valve. I was using the air pump, I was also inadvertently was rocking the valve because I was supporting it with my hand. Then powie, the valve partially ripped out the tube.
 

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Technique

lawrence said:
Someone in my bike club suggested when you ride, loosen the nut all the way on your presta valve and when you blow up the tire, tighted the nut. The reasoning for this is if the nut is loose when you are riding and you get a flat, sometimes the tube will move inside the rim/tire. If the nut is loose, it will slip which is good. If the nut is tight, when you have a flat and the tube moves, it puts stress on the rubber around the valve and it could rip either then or later. When you are putting air in the tube, tighten the nut to prevent the valve from moving and thus ripping the valve out of the tube.

He suggested this as when I had a flat yesterday and I put in a new Michelin tube with a smooth valve. I was using the air pump, I was also inadvertently was rocking the valve because I was supporting it with my hand. Then powie, the valve partially ripped out the tube.
The real thing to do with the valve nut is to throw it away. It serves no purpose except to make it easy for a shop to inflate a tube with a compressor head without having to worry about supporting the valve stem. Your problem with tearing the stem out of the tube is a technique issue, and haveing the valve nut would not have helped much, if at all. There is no reason to do what you did. The method is to have the valve stem at the top (12:00) and to slightly lift the bike by pushing up on the pump while you're pumping. This keeps the pump head firmly on the valve and allows the wheel/bike to move without putting so much stress on the valve stem.
 

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Kerry Irons said:
The real thing to do with the valve nut is to throw it away. It serves no purpose except to make it easy for a shop to inflate a tube with a compressor head without having to worry about supporting the valve stem. Your problem with tearing the stem out of the tube is a technique issue, and haveing the valve nut would not have helped much, if at all. There is no reason to do what you did. The method is to have the valve stem at the top (12:00) and to slightly lift the bike by pushing up on the pump while you're pumping. This keeps the pump head firmly on the valve and allows the wheel/bike to move without putting so much stress on the valve stem.
I always wondered about that little nut. What about the valve cap? I know Schrader valves always have to be capped in case the valve fails so you end up with a slow leak instead of a near blow-out. Is it the same with the Presta?
 

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California L33 said:
I always wondered about that little nut. What about the valve cap? I know Schrader valves always have to be capped in case the valve fails so you end up with a slow leak instead of a near blow-out. Is it the same with the Presta?
If a Schrader valve stem blew, most caps would do absolutely nothing.

On either Schrader or Presta, the valve caps are there purely to keep the valve innards clean - dirt in the valve would result in an incomplete seal.
 

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achiral said:
If a Schrader valve stem blew, most caps would do absolutely nothing.

On either Schrader or Presta, the valve caps are there purely to keep the valve innards clean - dirt in the valve would result in an incomplete seal.
Given that you screw the Presta valve closed after inflation, is there any value to the valve cap on a Presta valve? Does it provide any protection? Many of the pro team bikes I saw at the Tour de Georgia did not have valve caps.
 

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achiral said:
If a Schrader valve stem blew, most caps would do absolutely nothing.

On either Schrader or Presta, the valve caps are there purely to keep the valve innards clean - dirt in the valve would result in an incomplete seal.
Back in the good old days when California had random vehicle inspections they looked for valve caps on every tire. (I've seen safety check lists that still have this.) The logic was that if the stem failed with no cap, the tire would loose pressure so fast it may as well be a blow out, but if the cap were in place the air would leak out slowly enough that the driver could pull over without loosing control. (In case there's confusion, when I talk about 'stem' I'm not talking about the rubber stem that houses the valve, but the threaded metal stem that forms part of the valve in a Schraeder tire. I don't know how Presta valve work.)
 

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As others have said pitch the nuts and the caps. Zero purpose in their existence. If the nuts served any value, you'd think Michelin would have issues with their threadless stems, wouldn't ya? And there is NO way that dirt is going to foul a presta valve that is closed. Can't happen 'cuz, well, it's closed.
 

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alienator said:
As others have said pitch the nuts and the caps. Zero purpose in their existence. If the nuts served any value, you'd think Michelin would have issues with their threadless stems, wouldn't ya? And there is NO way that dirt is going to foul a presta valve that is closed. Can't happen 'cuz, well, it's closed.
Of course you don't need the cap - its purpose is to keep everything a little bit cleaner. Do a hundred miles in sloppy conditions or 1000 in normal conditions and the whole assembly gets covered with road grime. If you use a valve cap, the next time you inflate the tube the valve assembly is always clean.

It's not as if the cap realistically saves any weight, anyway, In a race you'll probably be swapping wheels so the additional 3 seconds to take off a valve cap when fixing a flat is irrelevant.


Presta and Schrader valves work in more or less the same manner. The main differences are the external housing and the ability to lock a Presta valve shut. Take a Schrader valve and cut off part of the threaded housing and you get something remarkably similar to a Presta valve.
 

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I havent logged 10's of 1000's of miles but have got a few under my belt and i've NEVER had to clean a stem before putting air in it and i've never used the cap. Now maybe thats just me.
 

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I hate to wait on someone out on the road when they get a flat. It drives me crazy waiting for them to spin the little nut off and then to spin the little nut on. I know it doesn't take that long but it is long enough for me to mutter "Why" for 32 times in a row.
 
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