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How much air goes from the tire to the pump when you plug it on the valve?

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How much air goes from the tire to the pump when you plug it on the valve?

Old 04-19-21, 11:08 AM
  #26  
datlas 
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Originally Posted by cxwrench
Wrong. As someone else ( DaveSSS ) posted earlier as soon as you stop pumping the pressure in the tube forces the valve closed. You don't lose any pressure from a presta valve when removing the pump head. The air you hear is coming from the pump, not the tube. It's no 'theory'...the pump head doesn't depress the valve, air pressure from the pump does. You continue to get a pressure reading when you stop pumping because there is still positive pressure in the pump/hose. Oddly enough it's the same as what the pressure is in the tube.
One confounding issue is that SOME pumps do NOT depress the valve when you put the chuck on. These are the ones you are probably referring to.

However, SOME OTHER pumps DO INDEED depress the valve when you put the chuck on. This is the type the OP has.
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Old 04-19-21, 11:10 AM
  #27  
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Here is a pump with an integrated bleed valve on the pump head.
Blackburn Core Pro Floor Pump | The Colorado Cyclist
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Old 04-19-21, 11:13 AM
  #28  
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Originally Posted by big john
Here is a pump with an integrated bleed valve on the pump head.
Blackburn Core Pro Floor Pump | The Colorado Cyclist
I wonder how much pressure the tire loses when you put the pump on?
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Old 04-19-21, 11:18 AM
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I've never seen one that does depress the valve when the head is put on, but I guess that doesn't mean they couldn't exist. But...they still wouldn't release any meaningful amount of air when removed because as soon as you stop putting pressure on the valve it closes...instantaneously.
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Old 04-19-21, 11:24 AM
  #30  
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Originally Posted by cxwrench
I've never seen one that does depress the valve when the head is put on, but I guess that doesn't mean they couldn't exist. But...they still wouldn't release any meaningful amount of air when removed because as soon as you stop putting pressure on the valve it closes...instantaneously.
I have a Silca Tattico mini pump. If I push the head on too far, something stops the valve from closing. I don't know if it's something depressing the lock nut or the rubber gasket grabs the side of the lock nut and holds the valve open, but the valve definitely doesn't close. Because the gasket holds the valve stem so tightly, a lot of air can escape before I can pull the pump off. But that's all user error. If I don't push the head on too far, everything is fine.
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Old 04-19-21, 11:24 AM
  #31  
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Originally Posted by cxwrench
I've never seen one that does depress the valve when the head is put on, but I guess that doesn't mean they couldn't exist. But...they still wouldn't release any meaningful amount of air when removed because as soon as you stop putting pressure on the valve it closes...instantaneously.
I don't recall using one that didn't, if you push it on far enough.

Of course it wouldn't lose air if you got it straight off. I was talking about the times when you have a little trouble pulling it off cleanly.

And I don't say "brifters" either.
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Old 04-19-21, 11:31 AM
  #32  
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Originally Posted by cxwrench
I've never seen one that does depress the valve when the head is put on, but I guess that doesn't mean they couldn't exist. But...they still wouldn't release any meaningful amount of air when removed because as soon as you stop putting pressure on the valve it closes...instantaneously.
Here's one that I have, (Pro Team Digital)
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Old 04-19-21, 11:48 AM
  #33  
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Originally Posted by eduskator
I was just wondering since when people started to give their two cents instead of trying to answer the damn question.
We haven't even gotten to the point of the thread where we blame you for it being possible to lose air in the first place. Give us a few more pages.
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Old 04-19-21, 12:02 PM
  #34  
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Originally Posted by big john
So you're saying you get no reading on the gauge when you first install the pump head? I have two floor pumps with different heads and they both show pressure before pumping.
Sometimes when trying to remove the pump head after inflating the tire if it's in an awkward position and I twist it around air will escape from the tire. Sure, if it is removed straight off the only air released is from the hose but if you fumble around with it the tire will lose air.
Yes, that's what we're saying. Silca heads never press the top nut down. Any head that does that defeats the whole purpose of using presta valve stems. I recently bought a hirame pump head. Pricey, but really nice. It's got an easy to push lever to clamp it to the stem. The collar adjusts to difference stem diameter. Some valve stems for tubeless have a no-thread small diameter right at the top.

https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
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Old 04-19-21, 12:04 PM
  #35  
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Originally Posted by DaveSSS
Yes, that's what we're saying. Silca heads never press the top nut down. Any head that does that defeats the whole purpose of using presta valve stems. I recently bought a hirame pump head. Pricey, but really nice. It's got an easy to push lever to clamp it to the stem. The collar adjusts to difference stem diameter. Some valve stems for tubeless have a no-thread small diameter right at the top.

https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
Not to further derail the thread, but +1 for the Hirame pump head. It's the best, Jerry. THE BEST!!
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Old 04-19-21, 12:07 PM
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Originally Posted by cxwrench
Wrong.
Incorrect.
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Old 04-19-21, 12:12 PM
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Originally Posted by DaveSSS
Any head that does that defeats the whole purpose of using presta valve stems.
"No true Scotsman Presta pump," eh?
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Old 04-19-21, 12:16 PM
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Originally Posted by DaveSSS
Yes, that's what we're saying. Silca heads never press the top nut down. Any head that does that defeats the whole purpose of using presta valve stems. I recently bought a hirame pump head. Pricey, but really nice. It's got an easy to push lever to clamp it to the stem. The collar adjusts to difference stem diameter. Some valve stems for tubeless have a no-thread small diameter right at the top.

https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
From Road Bike Rider:"Most production pumps come with proprietary chucks and while there are almost endless designs, the majority work similarly. You press them onto valves before locking them in place with the built-in lever.

Because the Presta valve is open when you do this, pressing the pump head on usually pushes the valve tip down opening the valve and releasing some air. If a person is fumble fingered when putting on this type of chuck, they can lose a lot or almost all the air in the tire meaning more pumping is required. If you were trying to only top of the tire before a ride this can be annoying."

This is what is familiar to me. The last pump head I wore out would lose all the air before I could inflate a tire, it was leaking so bad. Obviously it was holding the valve open. I admit to not having a Silca pump head in my arsenal.
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Old 04-19-21, 02:17 PM
  #39  
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Originally Posted by Seattle Forrest
We haven't even gotten to the point of the thread where we blame you for it being possible to lose air in the first place. Give us a few more pages.
I can't wait to get my arse roasted.

Originally Posted by cxwrench
I've never seen one that does depress the valve when the head is put on, but I guess that doesn't mean they couldn't exist. But...they still wouldn't release any meaningful amount of air when removed because as soon as you stop putting pressure on the valve it closes...instantaneously.
I have the Giant Control Tower Boost (not a cheap one at all) and it does it. As soon as I plug the head, I can hear the nice sound of air inside the tire pressurizing the pump's hose and the needle rising up like the sun every morning! It's like music to my ears.
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Old 04-19-21, 02:57 PM
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Originally Posted by eduskator
I have the Giant Control Tower Boost (not a cheap one at all) and it does it. As soon as I plug the head, I can hear the nice sound of air inside the tire pressurizing the pump's hose and the needle rising up like the sun every morning! It's like music to my ears.
Does yours have a universal head on it that'll service Presta and Schrader through the same nozzle? My pump does and it exhibits the same behavior; I'm thinking that it might be common or even necessary for that type of head.
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Old 04-19-21, 03:28 PM
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I also have a couple of old brass silca heads with no lever. They have a thick rubber bushing with a hole size that is controlled by a threaded collar. As the hole gets larger, tighten the collar some more. Only friction holds it in place.

https://www.biketiresdirect.com/prod...-presta-chucks
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Old 04-19-21, 04:14 PM
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The forum can now be shut down. Every conceivable question has now been asked.
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Old 04-19-21, 04:27 PM
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Originally Posted by WhyFi
Does yours have a universal head on it that'll service Presta and Schrader through the same nozzle? My pump does and it exhibits the same behavior; I'm thinking that it might be common or even necessary for that type of head.
Yes! It's called ''Autohead'' if I recall correctly.

It's an interesting theory.
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Old 04-19-21, 05:24 PM
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Originally Posted by WhyFi
Does yours have a universal head on it that'll service Presta and Schrader through the same nozzle? My pump does and it exhibits the same behavior; I'm thinking that it might be common or even necessary for that type of head.
Agree.
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Old 04-19-21, 05:24 PM
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I think it's hilarious that so many people don't understand the specific purpose of a presta valve. It was invented long ago and pump manufacturers have decided to negate the design with stupid pump heads. I have one silca head that has a thread-on Schrader connection at the top, so both can be used.
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Old 04-19-21, 05:31 PM
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Originally Posted by DaveSSS
I think it's hilarious that so many people don't understand the specific purpose of a presta valve. It was invented long ago and pump manufacturers have decided to negate the design with stupid pump heads. I have one silca head that has a thread-on Schrader connection at the top, so both can be used.
I think it's hilarious that you think that people don't understand it and that you think that this type of pump head negates the purpose of the valve; it still snaps shuts with negligible air loss unless you really fumble**** the head removal. Meanwhile, I can pump up the tires on both my bike and my kids' and wife's bikes with no fuss.
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Old 04-19-21, 05:36 PM
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Originally Posted by jrobe
The forum can now be shut down. Every conceivable question has now been asked.
Whatever, stupid people are really creative. Watch this:

I want to recreate that Rapha commercial, is it more important for a floor pump to be light weight or aero?
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Old 04-19-21, 05:38 PM
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Originally Posted by Seattle Forrest
Whatever, stupid people are really creative. Watch this:

I want to recreate that Rapha commercial, is it more important for a floor pump to be light weight or aero?
No, no, no - it's the bidon that needs to be both light *and* aero for the flippy twirl.
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Old 04-19-21, 06:13 PM
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Ask the manufacturer of your deep profile carbon rims if it's OK to drill out their rims for a Schrader valve.
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Old 04-19-21, 06:34 PM
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A presta pump that mechanically depresses the valve is an abomination.

But the answer is clearly 42psi for a high pressure tire, 4.2psi for a low pressure tire, and 0.42bar for the civilized world.
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