|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
valve and pressure question
I'm a newbie. I haven't seriously ridden bicycles since I was
in high school, which was thirty years ago. Recently I bought a nice used Cannondale, and am still getting back into it. So bear with me, if you will. I bought a floor pump (Blackburn Airtower 4) fitted with two terminals, one for Shrader valves and the other for Prestas. I have Prestas. The pump also has a pressure gauge. My tires are rated for 80psi. If I pump them to that pressure by the pump's gauge, and then check with a handheld digital gauge and a Shrader/Presta adapter, they show about 56psi. If I then leave the adapter on the valve stem and attach the pump via the Shrader side of the hose, I also see 56psi. So I pump it up to 80, and check again with the handheld gauge. Dead on. So I'm seeing two different pressure readings, depending on the presence of the adapter and which terminus of the pump I'm using. The tires feel like the readings with the adapter are probably right, based on my thirty-year-old experience. So I'm probably going to just continue using it, unless somene raises a red flag. I'm curious about what might be going on here, though. Could the adapter possibly make that much difference? Thanks. -- Mark Shaw moc TOD liamg TA wahsnm ================================================== ====================== "All of my mistakes are giving me ideas." - Natalie Lileks |
Ads |
#2
|
|||
|
|||
On Fri, 08 Apr 2005 14:24:15 +0000, Mark Shaw wrote:
So I'm seeing two different pressure readings, depending on the presence of the adapter and which terminus of the pump I'm using. I take it the pump is one of those double-headed jobs, with Shader on one side of the head, Presta on the other. The air pressure is read, though, back at the pump body, so it should not even know what end is used. Something is wrong. Chances are that the separate pressure gauge is correct. Take your pump back to the shop where you got it and explain your situation. I guess the pump is somehow defective, with some blockage in the presta side of the head. -- David L. Johnson __o | "A foolish consistency is the hobgoblin of little minds, adored _`\(,_ | by little statesmen and philosophers and divines." --Ralph Waldo (_)/ (_) | Emerson |
#3
|
|||
|
|||
"David L. Johnson" wrote: (clip) I guess the pump is somehow defective, with some blockage in the presta side of the head. ^^^^^^^^^^^^^^ If you operate the pump with the Presta setting, but not connected to a valve, does it register any pressure on the gauge? Compare this to the Shraeder setting. Is there a difference? On the Presta setting can you compress air, so you have a gauge reading that does not bleed off? It could be that there is a scrap of rubber in the valve that is blocking air flow. |
#4
|
|||
|
|||
Leo Lichtman wrote: "David L. Johnson" wrote: (clip) I guess the pump is somehow defective, with some blockage in the presta side of the head. ^^^^^^^^^^^^^^ If you operate the pump with the Presta setting, but not connected to a valve, does it register any pressure on the gauge? Compare this to the Shraeder setting. Is there a difference? On the Presta setting can you compress air, so you have a gauge reading that does not bleed off? It could be that there is a scrap of rubber in the valve that is blocking air flow. I think I will give some advice on this one....ummmmm......maybe not. TGIF. Maggie |
#5
|
|||
|
|||
Leo Lichtman wrote:
"David L. Johnson" wrote: (clip) I guess the pump is somehow defective, with some blockage in the presta side of the head. ^^^^^^^^^^^^^^ If you operate the pump with the Presta setting, but not connected to a valve, does it register any pressure on the gauge? Compare this to the Shraeder setting. Is there a difference? On the Presta setting can you compress air, so you have a gauge reading that does not bleed off? It could be that there is a scrap of rubber in the valve that is blocking air flow. There's no "setting" per se, just two holes in the chuck end of the hose - one for Presta, the other for Schrader. They both seem to be able to hold compressing air pretty well. I'll just take it back to the shop and ask them to check it out. It could very well be that I'm not using it correctly. -- Mark Shaw moc TOD liamg TA wahsnm ================================================== ====================== "All of my mistakes are giving me ideas." - Natalie Lileks |
#6
|
|||
|
|||
Mark Shaw wrote:
There's no "setting" per se, just two holes in the chuck end of the hose - one for Presta, the other for Schrader. They both seem to be able to hold compressing air pretty well. I'll just take it back to the shop and ask them to check it out. It could very well be that I'm not using it correctly. Well, I took it in. And the tech demostrated it working perfectly on their bike. So I don't know what's up. I'll continue playing with it; maybe I released too much air. The Presta valve is a new thing to me.... Thanks for all the help. -- Mark Shaw moc TOD liamg TA wahsnm ================================================== ====================== "All of my mistakes are giving me ideas." - Natalie Lileks |
#7
|
|||
|
|||
On Fri, 8 Apr 2005 14:24:15 +0000 (UTC), Mark Shaw
wrote: I'm a newbie. I haven't seriously ridden bicycles since I was in high school, which was thirty years ago. Recently I bought a nice used Cannondale, and am still getting back into it. So bear with me, if you will. Right on, good move. Enjoy the riding, welcome to the group. --- "BitwiseBob" - Bob Anderson Eugene Oregon |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
reccomended tire pressure? | Bob22b | Unicycling | 1 | January 30th 05 07:56 PM |
Rec.Bicycles Frequently Asked Questions Posting Part 1/5 | Mike Iglesias | General | 4 | October 29th 04 07:11 AM |
presta valve screws out | Paul Nevai | Techniques | 15 | September 13th 04 04:03 AM |
Shock Pump Newbie Question | Tony Scilipoti | Techniques | 5 | August 26th 04 01:33 PM |
Tyre suddenly leaks air at valve. HELP! | gkmac | Unicycling | 5 | December 16th 03 11:20 PM |