How much air goes from the tire to the pump when you plug it on the valve?
#26
Should Be More Popular
Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,049
Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix
Mentioned: 560 Post(s)
Tagged: 2 Thread(s)
Quoted: 22596 Post(s)
Liked 8,925 Times
in
4,158 Posts
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.
However, SOME OTHER pumps DO INDEED depress the valve when you put the chuck on. This is the type the OP has.
Last edited by datlas; 04-19-21 at 11:12 AM.
#27
Senior Member
Join Date: Sep 2005
Location: In the foothills of Los Angeles County
Posts: 25,286
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 8279 Post(s)
Liked 9,033 Times
in
4,471 Posts
Here is a pump with an integrated bleed valve on the pump head.
Blackburn Core Pro Floor Pump | The Colorado Cyclist
Blackburn Core Pro Floor Pump | The Colorado Cyclist
#28
Should Be More Popular
Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,049
Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix
Mentioned: 560 Post(s)
Tagged: 2 Thread(s)
Quoted: 22596 Post(s)
Liked 8,925 Times
in
4,158 Posts
Here is a pump with an integrated bleed valve on the pump head.
Blackburn Core Pro Floor Pump | The Colorado Cyclist
Blackburn Core Pro Floor Pump | The Colorado Cyclist
Likes For datlas:
#29
Senior Member
Join Date: Jul 2013
Location: Nor-Cal
Posts: 3,767
Bikes: lots
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1958 Post(s)
Liked 2,932 Times
in
1,489 Posts
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.
#30
Senior Member
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.
Likes For asgelle:
#31
Senior Member
Join Date: Sep 2005
Location: In the foothills of Los Angeles County
Posts: 25,286
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 8279 Post(s)
Liked 9,033 Times
in
4,471 Posts
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.
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.
Likes For big john:
#32
Senior Member
Join Date: Sep 2015
Posts: 598
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 389 Post(s)
Liked 255 Times
in
165 Posts
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.
#33
Senior Member
Join Date: Mar 2010
Location: Seattle, WA
Posts: 23,208
Mentioned: 89 Post(s)
Tagged: 0 Thread(s)
Quoted: 18883 Post(s)
Liked 10,646 Times
in
6,054 Posts
#34
Senior Member
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.
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.
https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
#35
Should Be More Popular
Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,049
Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix
Mentioned: 560 Post(s)
Tagged: 2 Thread(s)
Quoted: 22596 Post(s)
Liked 8,925 Times
in
4,158 Posts
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
https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
Likes For datlas:
#36
Senior Member
Join Date: Jan 2010
Location: TC, MN
Posts: 39,520
Bikes: R3 Disc, Haanjo
Mentioned: 354 Post(s)
Tagged: 1 Thread(s)
Quoted: 20810 Post(s)
Liked 9,456 Times
in
4,672 Posts
Likes For WhyFi:
#37
Senior Member
Join Date: Jan 2010
Location: TC, MN
Posts: 39,520
Bikes: R3 Disc, Haanjo
Mentioned: 354 Post(s)
Tagged: 1 Thread(s)
Quoted: 20810 Post(s)
Liked 9,456 Times
in
4,672 Posts
#38
Senior Member
Join Date: Sep 2005
Location: In the foothills of Los Angeles County
Posts: 25,286
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 8279 Post(s)
Liked 9,033 Times
in
4,471 Posts
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
https://www.amazon.com/KUWAHARA-HIRA...31473976&psc=1
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.
#39
Senior Member
Thread Starter
Join Date: Aug 2019
Location: Québec, Canada
Posts: 2,112
Bikes: SL8 Pro, TCR beater
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 988 Post(s)
Liked 584 Times
in
439 Posts
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.
#40
Senior Member
Join Date: Jan 2010
Location: TC, MN
Posts: 39,520
Bikes: R3 Disc, Haanjo
Mentioned: 354 Post(s)
Tagged: 1 Thread(s)
Quoted: 20810 Post(s)
Liked 9,456 Times
in
4,672 Posts
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.
#41
Senior Member
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
https://www.biketiresdirect.com/prod...-presta-chucks
#44
Should Be More Popular
Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,049
Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix
Mentioned: 560 Post(s)
Tagged: 2 Thread(s)
Quoted: 22596 Post(s)
Liked 8,925 Times
in
4,158 Posts
Agree.
#45
Senior Member
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.
#46
Senior Member
Join Date: Jan 2010
Location: TC, MN
Posts: 39,520
Bikes: R3 Disc, Haanjo
Mentioned: 354 Post(s)
Tagged: 1 Thread(s)
Quoted: 20810 Post(s)
Liked 9,456 Times
in
4,672 Posts
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.
Likes For WhyFi:
#47
Senior Member
Join Date: Mar 2010
Location: Seattle, WA
Posts: 23,208
Mentioned: 89 Post(s)
Tagged: 0 Thread(s)
Quoted: 18883 Post(s)
Liked 10,646 Times
in
6,054 Posts
Likes For Seattle Forrest:
#48
Senior Member
Join Date: Jan 2010
Location: TC, MN
Posts: 39,520
Bikes: R3 Disc, Haanjo
Mentioned: 354 Post(s)
Tagged: 1 Thread(s)
Quoted: 20810 Post(s)
Liked 9,456 Times
in
4,672 Posts
#49
Senior Member
Ask the manufacturer of your deep profile carbon rims if it's OK to drill out their rims for a Schrader valve.
Likes For DaveSSS:
#50
Senior Member
Join Date: Oct 2008
Location: Portland, OR
Posts: 3,842
Bikes: Trek Domane SL6 Gen 3, Soma Fog Cutter, Focus Mares AL, Detroit Bikes Sparrow FG, Volae Team, Nimbus MUni
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 896 Post(s)
Liked 2,063 Times
in
1,081 Posts
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.
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.
Likes For downtube42: