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Old 11-27-13, 08:19 AM   #1
Still Pedaling
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Pump with a pressure release system

I'm trying to locate a stand up tire pump with a pressure release system allowing you to remove the flip-chuck without letting out air from the inner tube. I'm finding that with the smaller 14" tubes, the air pressure drops so much that I have to slightly over inflate to allow for the loss when removing the chuck. There are decent pumps that have a pressure release system, but from what I have seen so far they are designed for the Presta Valves and I'm not sure if they will work with the Schraeder Valve on the Brompton. Has anyone seen such a pump? I'm not sure, but I think someone posted info on this but I can't find it.

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Wayne
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Old 11-27-13, 08:35 AM   #2
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Both a presta and schraeder valve should close almost instantly once the chuck is removed unless it gets hung up. The air that you hear escaping is from the pump and hose.

How are you checking for the pressure drop? If using the pump's gauge, air filling the hose is enough to drop pressure. If using a pencil gauge, it's pretty easy to bleed off air before getting a reading. Plus those pencil gauges aren't very accurate. As a matter of fact, pump gauges aren't that accurate. I had a pump that read 20 PSI low at 100 PSI. In other words, it said 80 PSI.

As long as 'slightly over inflate' doesn't exceed the tire or rim recommendations, I'd recommend just doing that.
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Old 11-27-13, 09:18 AM   #3
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Originally Posted by JerrySTL View Post
Both a presta and schraeder valve should close almost instantly once the chuck is removed unless it gets hung up. The air that you hear escaping is from the pump and hose.

How are you checking for the pressure drop? If using the pump's gauge, air filling the hose is enough to drop pressure. If using a pencil gauge, it's pretty easy to bleed off air before getting a reading. Plus those pencil gauges aren't very accurate. As a matter of fact, pump gauges aren't that accurate. I had a pump that read 20 PSI low at 100 PSI. In other words, it said 80 PSI.

As long as 'slightly over inflate' doesn't exceed the tire or rim recommendations, I'd recommend just doing that.
Part of the problem might be from the chuck being hung up, and any amount of air that does escape from the tube depletes the pressure quit a bit considering that we are dealing with a small tube size. I didn't notice such a problem with the 26" tubes of my MB.

I agree, those pencil gauges do present a problem and they pretty much just give you a ball park figure. I have a pretty decent gauge, but the problem I'm having is that with the cramped room on the small wheels I find it difficult to get the gauge on/off the valve without letting some air out, and some air in a small tire tends to be a lot regarding pressure. I'm thinking that having a pump where you can remove the pressure in the hose will allow for a much smoother removal of the chuck. Well at least I'm hoping.
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Old 11-27-13, 11:44 AM   #4
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There is a check valve in the base of the Floor pump, and a check valve in the valve stem.
the air in the hose is not precious..


Wayne, consider getting a separate tire gage.. GH Meiser (US) made the ones in my tool box
high pressure range, dial reading, up to 140psi..

Last edited by fietsbob; 11-27-13 at 12:47 PM.
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Old 11-27-13, 12:11 PM   #5
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All Lezyne floor pumps have a bleed.
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Old 11-27-13, 05:29 PM   #6
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Quote:
Originally Posted by Still Pedaling View Post
Part of the problem might be from the chuck being hung up, and any amount of air that does escape from the tube depletes the pressure quit a bit considering that we are dealing with a small tube size. I didn't notice such a problem with the 26" tubes of my MB.

I agree, those pencil gauges do present a problem and they pretty much just give you a ball park figure. I have a pretty decent gauge, but the problem I'm having is that with the cramped room on the small wheels I find it difficult to get the gauge on/off the valve without letting some air out, and some air in a small tire tends to be a lot regarding pressure. I'm thinking that having a pump where you can remove the pressure in the hose will allow for a much smoother removal of the chuck. Well at least I'm hoping.
I had a few floor pumps that were difficult to remove. So much that I tore off a few presta valves. Then I got a Specialized pump that releases very easily. The head automatically adapts to both presta and schraeder valves. There might be a problem with the SwitchHitter II head being a little too big to get between the spokes on your smaller wheels.

http://www.specialized.com/us/en/ftb...-hp-floor-pump

Another thought would be to get a valve adapter with a bend in it to make it easier to get the pump on it. Maybe zip-tie it up to a spoke. Here's one made by Topeak and has a check valve in it to prevent loss of air pressure. It even says it's for small wheels!

http://www.ebay.com/itm/Topeak-Press...item417215440b

Can you get presta valve tubes for that wheel? If so you could get a grommet to adapt the presta to the hole. You might have better luck with a presta valve.
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Old 11-27-13, 07:56 PM   #7
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All Lezyne floor pumps have a bleed.
Sort of. Wayne has Schrader valves on his Brompton, and the push botton on the Lezyne chucks works a little different with them. I can't describe the difference any better than Lezyne; "When using an ABS equipped Lezyne floor pump to inflate a Presta valve tube, pressing the ABS button releases the air back pressure. Releasing this back pressure allows for the easy removal of the Flip-Thread Chuck without the risk of unscrewing removable Presta valve cores. When inflating Schrader valve tubes, pressing the ABS button releases air from the tube to adjust tire pressure". Note the last part, that's exactly what he doesn't want to do.

Switching to Presta tubes with adapters (metal or rubber grommet type, depending on rim construction) and using a Lezyne floor pump with their optional press on right angle chuck (Presta only) might be another option, but I can't directly vouch for the fit/ease of use because the current designs didn't exist when I was riding Bromptons. I never really found anything I was truly happy with back then, but I have used the described combination on 18" and 20" geared hub and generator hub and 36 spoke wheels (which also have access limitations), and so far I'm liking it. Lezyne pumps in general are hard to beat.

Schwalbe tubes with all metal stems seem hold up better than some other brands, particularly in applications involving friction chucks that have to be pulled off (while also appearing to be superior with twisty type chucks too).

John
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Old 11-29-13, 07:28 AM   #8
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Quote:
Originally Posted by jmm View Post
Sort of. Wayne has Schrader valves on his Brompton, and the push botton on the Lezyne chucks works a little different with them. I can't describe the difference any better than Lezyne; "When using an ABS equipped Lezyne floor pump to inflate a Presta valve tube, pressing the ABS button releases the air back pressure. Releasing this back pressure allows for the easy removal of the Flip-Thread Chuck without the risk of unscrewing removable Presta valve cores. When inflating Schrader valve tubes, pressing the ABS button releases air from the tube to adjust tire pressure". Note the last part, that's exactly what he doesn't want to do.
John
Ah, thanks for making that clear; I did not realize that.
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