Just curious, Schrader valve
#1
Senior Member
Thread Starter
Just curious, Schrader valve
Not a big deal but I was just curious when I was topping up my tires.
When you remove the pump from the schrader valve, how much psi is lost when when you get that hsss?
When you remove the pump from the schrader valve, how much psi is lost when when you get that hsss?
#2
Happy banana slug
Join Date: Sep 2015
Location: Arcata, California, U.S., North America, Earth, Saggitarius Arm, Milky Way
Posts: 3,693
Bikes: 1984 Araya MB 261, 1992 Specialized Rockhopper Sport, 1993 Hard Rock Ultra, 1994 Trek Multitrack 750, 1995 Trek Singletrack 930
Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 1531 Post(s)
Liked 1,527 Times
in
915 Posts
Basically none, the air's coming from the pump hose.
Likes For Korina:
#3
Senior Member
Join Date: Aug 2021
Location: Boston, MA
Posts: 519
Bikes: 2021 Trek FX Sport 4, ~1996 Mongoose Crossway 4.50
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 94 Post(s)
Liked 1,303 Times
in
432 Posts
I've wondered this myself (I'm like that). It's going to depend on the pressure and tire volume. I'm guessing around 0.5 psi.
Mark
Mark
#6
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,341
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6200 Post(s)
Liked 4,201 Times
in
2,357 Posts
That is true only for a Presta valve. Prestas are check valves that only allow air flow in one direction. Schrader valves have to be held open to fill. Any hissing is air being lost from the hose and tube. How much air is lost from the tube would depend on a number of factors and would be difficult to quantify. It would also vary widely.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Likes For cyccommute:
#7
Senior Member
Join Date: Mar 2010
Posts: 1,657
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1245 Post(s)
Liked 1,321 Times
in
673 Posts
That is true only for a Presta valve. Prestas are check valves that only allow air flow in one direction. Schrader valves have to be held open to fill. Any hissing is air being lost from the hose and tube. How much air is lost from the tube would depend on a number of factors and would be difficult to quantify. It would also vary widely.
#8
Senior Member
Join Date: Jan 2013
Posts: 2,674
Bikes: too many sparkly Italians, some sweet Americans and a couple interesting Japanese
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 567 Post(s)
Liked 563 Times
in
405 Posts
Easy to check and if your pump head is getting sloppy might be worth it to check with a gauge after inflating which will also catch gauge inaccuracies.
A clean Schrader value can work as well as a Presta in limiting the air escape as demonstrated by their use in high-pressure hydraulic systems on Aircraft.
A clean Schrader value can work as well as a Presta in limiting the air escape as demonstrated by their use in high-pressure hydraulic systems on Aircraft.
#9
Senior Member
Join Date: Jun 2002
Location: Montreal, Quebec
Posts: 5,921
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1815 Post(s)
Liked 1,693 Times
in
974 Posts
A lot will depend on the volume of the tire you are pumping. Most bicycles with tires that use schrader valves are high volume/lower pressure tires. With these tires very little pressure is lost and the pressure loss is of very little consequence
Likes For alcjphil:
Likes For Charliekeet:
#11
Senior Member
My old Fuji S-10S came with a screw-on hose for the factory Primus frame pump. I couldn't get that hose off the Schrader valve quick enough, losing lots of pressure while doing so. Soooo.... I ditched the Primus pump and got the Zefal HP with a quick-release chuck withn the first month or so. That old Fuji still wears a Zefal HP today, albeit it's fourth one for various reasons...
BTW, even back then, I was inflating my 27x1-1/8 tires to ~100psi. WITH Schrader valves!
BTW, even back then, I was inflating my 27x1-1/8 tires to ~100psi. WITH Schrader valves!
#12
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 14,949
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6177 Post(s)
Liked 4,794 Times
in
3,306 Posts
I suppose it depends on what type chuck you use for Schrader. However many that lock on to your valve stem probably release the pin almost as soon as you release the locking lever. Just like prestas, what's being heard is air escaping from the chuck, hose and sometimes the pump.
However if you have a 60 plus year old floor pump like I have with a chuck that you screw onto the Schrader valve, then yes there is some air loss while you race to unscrew it quickly. However I'd really be surprised if they make air chucks for bicycle floor pumps like that anymore.. Besides, it had no gauge on it so I still had to check with a gauge after I removed the chuck to see if the tire was full. So how much air is lost wasn't an issue since I had to check the pressure any how.
That pump is pretty much not used ever anymore. I only keep it around because it's been here as long as I've been here, maybe longer.
However if you have a 60 plus year old floor pump like I have with a chuck that you screw onto the Schrader valve, then yes there is some air loss while you race to unscrew it quickly. However I'd really be surprised if they make air chucks for bicycle floor pumps like that anymore.. Besides, it had no gauge on it so I still had to check with a gauge after I removed the chuck to see if the tire was full. So how much air is lost wasn't an issue since I had to check the pressure any how.
That pump is pretty much not used ever anymore. I only keep it around because it's been here as long as I've been here, maybe longer.
Last edited by Iride01; 10-20-21 at 08:59 AM.
Likes For Iride01:
#13
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,341
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6200 Post(s)
Liked 4,201 Times
in
2,357 Posts
If you hear hissing from a Schrader valve, air is being lost from the tube as well as the hose. With a Presta, air is being lost only from the hose.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#14
Full Member
However if you have a 60 plus year old floor pump like I have with a chuck that you screw onto the Schrader valve, then yes there is some air loss while you race to unscrew it quickly. However I'd really be surprised if they make air chucks for bicycle floor pumps like that anymore..
#15
Senior Member
Join Date: Mar 2010
Posts: 1,657
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1245 Post(s)
Liked 1,321 Times
in
673 Posts
Most pump heads I’ve seen and used for Schrader have a plunger that is nearly flush with the outside of the head. The pin of the plunger engages the valve almost as soon as the chuck is placed on the stem. The seal isn’t that tight around a Schrader valve either needing either a thumb lock or screw on mechanism to hold it in place. Flipping open the thumb lock or unscrewing the chuck results in some pressure loss (how much is difficult to quantify) because the pin engages the stem’s valve until it is clear of the stem.
If you hear hissing from a Schrader valve, air is being lost from the tube as well as the hose. With a Presta, air is being lost only from the hose.
If you hear hissing from a Schrader valve, air is being lost from the tube as well as the hose. With a Presta, air is being lost only from the hose.
#16
Senior Member
Join Date: Oct 2013
Location: Highlands Ranch, CO
Posts: 1,221
Bikes: '13 Diamondback Hybrid Commuter, '17 Spec Roubaix Di2, '17 Spec Camber 29'er, '19 CDale Topstone Gravel
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 590 Post(s)
Liked 445 Times
in
260 Posts
Hiss duration is a factor. How long do you hear the hiss? If you have to fumble around for a few seconds to get the pump nozzle off completely, while it's hissing the entire time, you're likely losing more air pressure from the tire than you want to.
Likes For Riveting:
#17
Senior Member
Join Date: Nov 2013
Posts: 1,085
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 440 Post(s)
Liked 264 Times
in
162 Posts
Easy to check and if your pump head is getting sloppy might be worth it to check with a gauge after inflating which will also catch gauge inaccuracies.
A clean Schrader value can work as well as a Presta in limiting the air escape as demonstrated by their use in high-pressure hydraulic systems on Aircraft.
A clean Schrader value can work as well as a Presta in limiting the air escape as demonstrated by their use in high-pressure hydraulic systems on Aircraft.
Likes For Bmach:
#18
Senior Member
Join Date: Feb 2015
Location: Mission Viejo
Posts: 5,801
Bikes: 1986 Cannondale SR400 (Flat bar commuter), 1988 Cannondale Criterium XTR, 1992 Serotta T-Max, 1995 Trek 970
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 1943 Post(s)
Liked 2,164 Times
in
1,323 Posts
The only way to tell is with a separate pressure gauge. The issue with that is the pump gauge may not be accurate.
You could use the pump on a car tire and then compare the pump reading with the pressure gauge. There is so much volume that a small amount probably won’t impact the reading. It will also indicate if your floor pump gauge is off.
I have an inexpensive floor pump that is off by 3psi. Not a big deal at 75psi, but more so at 30psi.
John
You could use the pump on a car tire and then compare the pump reading with the pressure gauge. There is so much volume that a small amount probably won’t impact the reading. It will also indicate if your floor pump gauge is off.
I have an inexpensive floor pump that is off by 3psi. Not a big deal at 75psi, but more so at 30psi.
John
Likes For 70sSanO:
Likes For MNBikeCommuter:
#20
Senior Member
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Posts: 29,546
Bikes: Bottecchia Sprint, GT Timberline 29r, Marin Muirwoods 29er, Trek FX Alpha 7.0
Mentioned: 112 Post(s)
Tagged: 0 Thread(s)
Quoted: 5223 Post(s)
Liked 3,579 Times
in
2,341 Posts
I'm a schrader user
related: when I check my tire pressure with a hand held gauge, a little air escapes. so when I'm deflating the tires on my Jeep, when I get close to the pressure I want, I use the gauge repeatedly to get it perfect. meaning the more I check the pressure, the lower it goes. because bike tires are so low in volume, checking the pressure may change the pressure more than one wants. so when you get it where you want it, leave it alone
related: when I check my tire pressure with a hand held gauge, a little air escapes. so when I'm deflating the tires on my Jeep, when I get close to the pressure I want, I use the gauge repeatedly to get it perfect. meaning the more I check the pressure, the lower it goes. because bike tires are so low in volume, checking the pressure may change the pressure more than one wants. so when you get it where you want it, leave it alone
#22
Senior Member
Join Date: Dec 2019
Posts: 954
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 263 Times
in
212 Posts
It must be very little because we use Schrader valves on mountain bike shocks. The pressure is about 80psi but the volume inside the shock is tiny. So if really any amount of air came out you would lose a lot of pressure.
#23
Palmer
Join Date: Mar 2007
Location: Parts Unknown
Posts: 8,601
Bikes: Mike Melton custom, Alex Moulton AM, Dahon Curl
Mentioned: 37 Post(s)
Tagged: 0 Thread(s)
Quoted: 1659 Post(s)
Liked 1,806 Times
in
1,052 Posts
Fun fact: the Schrader valve was patented in April 1893 by George Schrader of New York City, New York, USA.
Safety bicycle --> pneumatic tire --> Schrader valve
Safety bicycle --> pneumatic tire --> Schrader valve
Likes For tcs:
Likes For Fredo76:
#25
Senior Member
Join Date: Oct 2016
Location: Sacramento, CA
Posts: 458
Bikes: 2017 Surly Cross-Check. 2020 Specialized Turbo Vado 3.0, 2002 GT Dyno Roadster, 2002 Rans Stratus, 2020 Giant Fathom 2, 2011 Trek Pure Sport
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 171 Post(s)
Liked 85 Times
in
62 Posts