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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, 06:56 PM
  #51  
jaxgtr
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Originally Posted by eduskator
I am trying to figure out how much air my tires lose between rides by using my floor pump's pressure gauge. I was always told it could be between 0 to 20PSI, but I have never verified.

The thing is that there is a loss of pressure inside the tire as soon as I connect the head on the valve (physics ) so the reading is not accurate. I am trying to figure out how much pressure is lost during the connection. Google wasn't helpful. Just in case, I know I can buy a gauge to read the pressure directly at the valve.

Has anyone ever wondered / found the answer or am I the only bored cyclist in the world who has time to think about these things? I know it will vary based on the length of the pump's air hose and surely a few other factors, but there should be a known average, right?
Never was this interested....I dont seem to lose that much air, less than 3-5 lbs a week just off the top of my head.
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Old 04-19-21, 07:20 PM
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Old 04-19-21, 08:21 PM
  #53  
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Originally Posted by eduskator
Well what did you expect?
That happens even to good questions/threads, let alone wondering how much air it takes to fill a hose of unknown length from a tyre of unknown size and pressure, through coupling to a valve with unknown leakage/loss.
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Old 04-19-21, 09:57 PM
  #54  
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Originally Posted by DaveSSS
Ask the manufacturer of your deep profile carbon rims if it's OK to drill out their rims for a Schrader valve.
I guess I have to drill out all of my bikes wheels and convert them to Schrader because the minutia of Presta valves is to complex for me to grasp. I'm not worthy.
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Old 04-19-21, 10:03 PM
  #55  
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Originally Posted by WhyFi
No, no, no - it's the bidon that needs to be both light *and* aero for the flippy twirl.
God damnit, this is what happens when you go tubeless.
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Old 04-19-21, 10:04 PM
  #56  
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Originally Posted by Seattle Forrest
I want to recreate that Rapha commercial, is it more important for a floor pump to be light weight or aero?
Why not both?

I'm still amazed you amateurs are putting air in your tyres. 100% nitrogen is where it's at.
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Old 04-20-21, 06:21 AM
  #57  
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Originally Posted by Dean V
Well what did you expect?
That happens even to good questions/threads, let alone wondering how much air it takes to fill a hose of unknown length from a tyre of unknown size and pressure, through coupling to a valve with unknown leakage/loss.
Let's all calm down, everything will be OK. We're having fun here; that's what matters.
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Old 04-20-21, 08:08 AM
  #58  
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Originally Posted by znomit
Why not both?

I'm still amazed you amateurs are putting air in your tyres. 100% nitrogen is where it's at.
Where can I get pressurized nitrogen cartridges to carry on my rides? I think I'd rather have helium, actually.
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Old 04-20-21, 08:43 AM
  #59  
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Originally Posted by big john
Where can I get pressurized nitrogen cartridges to carry on my rides? I think I'd rather have helium, actually.
Good idea. I worked for a trucking company, that for a while, transported helium. 40 foot trailer with about 20 long tanks on it. It weighed 5000 LESS when it was fully loaded.
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Old 04-20-21, 09:12 AM
  #60  
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Originally Posted by Jack Tone
Good idea. I worked for a trucking company, that for a while, transported helium. 40 foot trailer with about 20 long tanks on it. It weighed 5000 LESS when it was fully loaded.
That's amazing.
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Old 04-20-21, 09:24 AM
  #61  
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Originally Posted by datlas
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.
You should always push the pump hose attachment on the valve only partly, not all the way that it may go (that is, unless you the good pump as you pointed out). It is attached wrongly when the air escapes into the pump hose. When that happens to me (my pump is not of the good sort), I re-attach the hose, sometimes need to do that twice before it is seated properly. But I agree that some pumps are constructed better way to prevent that to happen. With those other ones, you need to have a good sense not to push the hose head on the valve too deeply.

Thing is that if the attachment is depressing the valve stem, then you also loose some air pressure from the tire when you detach the hose or can lose a lot unless you really pull it off fast without any fumbling, not always easy to do.

Also, sticky valves is when you fill up at much longer intervals, like on bikes with bigger tires that run at lower pressures. I top up my 700x23s once a week but really should do that every three days or two if I was more picky.

Last edited by vane171; 04-20-21 at 09:30 AM.
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Old 04-20-21, 09:43 AM
  #62  
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Originally Posted by eduskator
Has anyone ever wondered / found the answer or am I the only bored cyclist in the world who has time to think about these things?
Yes / No / Yes.

Doesn't matter. That and the pressure gauge on the pump will never be the same as a hand pressure gauge because none of them are very accurate. What's more important is precision, not accuracy.

Pick one gauge and one pressure you like and stick with it.
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Old 04-21-21, 08:34 AM
  #63  
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Originally Posted by vane171
You should always push the pump hose attachment on the valve only partly, not all the way that it may go (that is, unless you the good pump as you pointed out). It is attached wrongly when the air escapes into the pump hose. When that happens to me (my pump is not of the good sort), I re-attach the hose, sometimes need to do that twice before it is seated properly. But I agree that some pumps are constructed better way to prevent that to happen. With those other ones, you need to have a good sense not to push the hose head on the valve too deeply.

Thing is that if the attachment is depressing the valve stem, then you also loose some air pressure from the tire when you detach the hose or can lose a lot unless you really pull it off fast without any fumbling, not always easy to do.

Also, sticky valves is when you fill up at much longer intervals, like on bikes with bigger tires that run at lower pressures. I top up my 700x23s once a week but really should do that every three days or two if I was more picky.
I don't think the loss of pressure is considerable enough to be a concern. The valve closes at the speed of light when you remove the pump's head.
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Old 04-21-21, 09:26 AM
  #64  
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Originally Posted by eduskator
That's typical forums for ya.

I love the guys who exclaim "This is not that interesting". Ok fine, you're not interested, you can leave without bothering to say anything.
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Old 04-21-21, 10:10 AM
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Originally Posted by BillyD
That's typical forums for ya.

I love the guys who exclaim "This is not that interesting". Ok fine, you're not interested, you can leave without bothering to say anything.
Yup. As I said a few pages back, I am always surprised when people give their opinion on the relevance of a question / thread instead of answering or trying to answer the question.

Makes me wonder if there should be a rule about not commenting on the form/manner, but rather on the substance.
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Old 04-21-21, 01:20 PM
  #66  
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I am always surprised when people ask such silly questions. Makes me wonder how they function and get through day to day life.

Of all the forums I'm a member on (I participate in some fishing, kayaking and car enthusiasts forums) this place takes the cake with the craziest comments and questions I've ever seen. One thing I've learned on this forum is that common sense isn't so common. I'm left scratching my head 70% of the time.
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Old 04-21-21, 02:36 PM
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Originally Posted by prj71
I am always surprised when people ask such silly questions. Makes me wonder how they function and get through day to day life.

Of all the forums I'm a member on (I participate in some fishing, kayaking and car enthusiasts forums) this place takes the cake with the craziest comments and questions I've ever seen. One thing I've learned on this forum is that common sense isn't so common. I'm left scratching my head 70% of the time.
See BillyD , another one!
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Old 04-21-21, 03:15 PM
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Well seriously...You asked a silly question.
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Old 04-21-21, 04:38 PM
  #69  
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Originally Posted by prj71
Well seriously...You asked a silly question.
Do you work in tech?
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Old 04-21-21, 08:34 PM
  #70  
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Originally Posted by big john
Where can I get pressurized nitrogen cartridges to carry on my rides? I think I'd rather have helium, actually.
I get my N2 cartridges here: Redrock Minnesota
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Old 04-21-21, 08:59 PM
  #71  
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Originally Posted by RGMN
I get my N2 cartridges here: Redrock Minnesota
  • Not for use with whip cream
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Old 04-22-21, 07:14 AM
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Originally Posted by colnago62
Do you work in tech?
I'm a design engineer and manager of product testing.

Definitely a lot of nipple flop cake going on in this thread.
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Old 04-22-21, 07:46 AM
  #73  
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Originally Posted by UCantTouchThis
Funny post. Get a gauge.

I inflate my tires, verify with gauge. All my floor pumps read differently vs the gauge. Specialized Air Tool, Lezyne steel, and the third, just got can't remember the model.

Lexzene always reads low so I inflate a bit more. Check with gauge. Checking with my gauge doesn't lose air vs attaching pumps. Though, if I am real careful and steady attaching, no air loss. Pull head straight off after inflation, just a hint of a hiss. No biggie.
Makes sense, assuming the gauge has an air release button, so you can make it a habit to intentionally over-inflate with the pump, and then use the gauge to release down to desired pressure. Otherwise you're playing a game of attaching pump and guessing how much to add after having read the gauge, and then we're back to wondering how much air is lost attaching that pump?

FYI, I think no matter how careful you are attaching your pump, you'll lose some air into at the least the pump's hose -- I think that's unavoidable, unless you're talking about a minipump that attaches right at the base of the pump and has no hose.
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Old 04-22-21, 08:00 AM
  #74  
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Originally Posted by Sy Reene
FYI, I think no matter how careful you are attaching your pump, you'll lose some air into at the least the pump's hose -- I think that's unavoidable, unless you're talking about a minipump that attaches right at the base of the pump and has no hose.
If you use presta valves with a chuck that doesn't press the valve like a Silca/Hirame/Hiro chuck it is quite easy to connect and not lose any air into a floor pump.
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Old 04-22-21, 08:05 AM
  #75  
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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.
This seems to imply that there's no way to release air out of the tube, without detaching these types of pump heads?
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