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Presta valves?

Old 07-09-11, 08:18 PM
  #1  
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Presta valves?

So, uh, here's a real dumb newb question that's probably been asked a million times:

What's the deal with Presta valves anyway? A little bit smaller hole in the rim? A tiny bit lighter? More "European," therefore "better?" (Facetious comment.) I love the comment in the thread about "the best $20 you ever spent on your bike" that says "11/32 drill bit to get rid of my Presta valves."

I plan to be riding a new bike next week, and it comes with the first Presta valves I've ever had. I'm sure I've lost the adaptors for all my various my pumps.

Are they just something irritatingly un-American, or is there some advantage? Are they the natural choice for a bike, while the Schrader is the natural valve for larger tires, only used on bikes in the States so we can use the pump at the gas station?

This doesn't have to be a serious, or even well informed discussion - I'm just wondering what's the deal?
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Old 07-09-11, 08:23 PM
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https://en.wikipedia.org/wiki/Presta_valve

https://www.bikeiowa.com/asp/features...?ArticleID=722

https://www.intownbicycles.com/bicycl...intenance#faq7
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Old 07-09-11, 08:31 PM
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Old 07-09-11, 08:37 PM
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Originally Posted by xrayzebra View Post
What's the deal with Presta valves anyway? A little bit smaller hole in the rim? A tiny bit lighter? More "European," therefore "better?" (Facetious comment.)
That's about it.

Decades ago there used to be an advantage for Presta when using bike frame pumps since the pumps made for Schrader valves required that you screw the hose onto the valve (now almost all pumps use a thumb-lock fitting). The end of the hose included a little nub to depress the Schrader valve and the result was that when you started to unscrew the hose you'd lose the last 10 or 20 psi of pressure that you'd just worked so hard to get into the tire.

But once Zefal came out with their HP series of pumps in the mid '70s with a thumb-lock fitting that worked with Schrader valves this advantage disappeared and both valve types are now equally easy (or hard) to inflate with a frame or mini pump. Of course now that Presta is the defacto standard for narrow road rims there aren't tubes available with the long valve stems needed on aero rims in any other valve style.
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Old 07-09-11, 08:53 PM
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Most road bike rims arent wide enough to safely fit the wider shrader valve, presta valves hold air much better, and dont arent effected by weathering/ corrosion.
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Old 07-09-11, 09:43 PM
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Presta's take some getting used to, but generally are better in a higher pressure tire. Whn you go to pump them up, open the valve and press on it once or twice to release some pressure before putting on the pump. Be sure to take the pump off in one straight motion, don't try to rock it back and forth off.
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Old 07-09-11, 09:49 PM
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Only have the air-pressure in the tube to overcome, with a hand pump,
as the valve has no return spring. ... it does have a locknut ..
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Old 07-09-11, 10:08 PM
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Originally Posted by fietsbob View Post
Only have the air-pressure in the tube to overcome, with a hand pump,
as the valve has no return spring. ... it does have a locknut ..
There's only air pressure to overcome with a Schrader valve as well. The pump head (or hose for some pumps) has a little nub that depresses the spring and opens the Schrader valve. None of your pumping force is doing anything to the valve spring.

As for other comments:
I have yet to see a rim so narrow that I couldn't safely ream out the hole a bit so that a Schrader valve would fit. And rims fail at spoke holes and because of braking surface wear - the valve hole is not the 'weak link' in my experience. There is of course a problem finding tubes with long stems with Schrader valves to use with deep, aero rims, but that's because of the market demand, not a technical issue.

Presta valves do not hold air better than Schrader. If they did then they'd be used in safety-critical applications like aviation tires and also where small air losses are critical such as high-pressure lab equipment. But they're not, Schrader valves are the ones of choice for these applications.

Yes, the valve cap on a Schrader valve is actually of some value in protecting the valve whereas it is not functional for Presta valves. But, OTOH, the Presta valve requires that you unscrew the locknut and 'burp' the valve. So the Schrader valve is still easier to work with even if you should replace the valve cap after inflation.
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Old 07-09-11, 10:28 PM
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Can't use Schrader stems on high profile aero rims.
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Old 07-10-11, 05:07 AM
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Originally Posted by prathmann View Post
There's only air pressure to overcome with a Schrader valve as well. The pump head (or hose for some pumps) has a little nub that depresses the spring and opens the Schrader valve. None of your pumping force is doing anything to the valve spring.
Yes. This is the problem. When you take the head off, you invariably lose some air reducing the pressure an unknown amount. The amount of air is inconsequential for a 35 psi huge auto tire, but it is very significant for a high pressure, low volume bike tire.
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Old 07-10-11, 09:48 AM
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Originally Posted by Looigi View Post
Yes. This is the problem. When you take the head off, you invariably lose some air reducing the pressure an unknown amount. The amount of air is inconsequential for a 35 psi huge auto tire, but it is very significant for a high pressure, low volume bike tire.
As stated in my first post, this used to be an issue 40 years ago when the hand pumps for Schrader valves required you to unscrew a hose from the valve and you'd lose some pressure in the process. With the thumblock pump heads that have been common ever since Zefal introduced their HP series pumps this is no longer an issue. Even with 125 psi, 20mm tires the air loss is insignificant - under 1 psi.
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Old 07-10-11, 10:22 AM
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Originally Posted by prathmann View Post
There's only air pressure to overcome with a Schrader valve as well. The pump head (or hose for some pumps) has a little nub that depresses the spring and opens the Schrader valve. None of your pumping force is doing anything to the valve spring.

As for other comments:
I have yet to see a rim so narrow that I couldn't safely ream out the hole a bit so that a Schrader valve would fit. And rims fail at spoke holes and because of braking surface wear - the valve hole is not the 'weak link' in my experience. There is of course a problem finding tubes with long stems with Schrader valves to use with deep, aero rims, but that's because of the market demand, not a technical issue.

Presta valves do not hold air better than Schrader. If they did then they'd be used in safety-critical applications like aviation tires and also where small air losses are critical such as high-pressure lab equipment. But they're not, Schrader valves are the ones of choice for these applications.

Yes, the valve cap on a Schrader valve is actually of some value in protecting the valve whereas it is not functional for Presta valves. But, OTOH, the Presta valve requires that you unscrew the locknut and 'burp' the valve. So the Schrader valve is still easier to work with even if you should replace the valve cap after inflation.
Because the Schrader valve spring has to be depressed each time, there is always some pressure loss when filling the tire. Simply openning the valve will result in more air needed in the tire than a Presta because the tire is pressurizing the hose and pump. Often there's lots of pressure loss if the seal between the pump chuck and the valve isn't good. And often there's significant pressure loss is simply removing the pump chuck. If the pump chuck hangs ups on the valve, the spring depressor can release pressure. It's still a problem with thumb locked pump heads for various reasons.

A presta valve could be operated without burping the valve because air pressure alone will open the valve. We customarily burp the valve to speed up the process but you don't really have to do that. You can't release any pressure from the presta valve by putting on the chuck - unless you are particularly ham-handed about it. The tire also doesn't fill up the hose/pump when you fill the tire. All of the air comes from the hose and pump.

Schrader valves are used in the automotive and aircraft industry because the tools exist for using them in those application. Airhose chucks exist and are wide spread for Schrader valves but the chucks for Presta are either rare or nonexistent. It's not a case of one is better than the other but a simple case of people in those industries don't know that Presta even exists.

I personally would love a set of Presta valves on my car. They would be much easier to fill than the Schrader valves. I find air hose chucks at filling stations frustrating to use because the alignment on the valve has to be just right or you leak air all over. When the stupid self-retracting hose is trying to self-retract because the locking mechanism is broken, I find it hard to stand on the hose so that it doesn't go pulling back and operate the valve chuck properly at the same time.

I don't know what high pressure laboratory equipment that you may have experience with but everything I've used or seen doesn't have a Schrader valve anywhere near it. For those applications, the lines providing the pressure are hard plumbed and rely on much more sophisticated valving than a spring loaded Schrader valve.
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Old 07-10-11, 10:35 AM
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I like that Presta valves have a threaded stem with a nut to keep the stem from retracting into the rim when putting the pump valve on the stem. Especially when filling up a brand new tube that doesn't have any air to provide resistance against the stem.
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Old 07-10-11, 10:40 AM
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Originally Posted by cyccommute View Post
Schrader valves are used in the automotive and aircraft industry because the tools exist for using them in those application. Airhose chucks exist and are wide spread for Schrader valves but the chucks for Presta are either rare or nonexistent. It's not a case of one is better than the other but a simple case of people in those industries don't know that Presta even exists.

I personally would love a set of Presta valves on my car. They would be much easier to fill than the Schrader valves. I find air hose chucks at filling stations frustrating to use because the alignment on the valve has to be just right or you leak air all over. When the stupid self-retracting hose is trying to self-retract because the locking mechanism is broken, I find it hard to stand on the hose so that it doesn't go pulling back and operate the valve chuck properly at the same time.

I don't know what high pressure laboratory equipment that you may have experience with but everything I've used or seen doesn't have a Schrader valve anywhere near it. For those applications, the lines providing the pressure are hard plumbed and rely on much more sophisticated valving than a spring loaded Schrader valve.
I'm going to disagree with a whole lot of that.

I don't work in a laboratory but I do know what an air conditioner looks like. Roughly 200 psi line pressure and the valve is expected not to lose ANY refrigerant. I won't tell you what kind of valve, you can look for yourself.

Filling either a bicycle tire or a car tire with an air compressor is MUCH faster and easier using Schrader valves because you don't need to thread on the chuck, just push it against the valve stem and inflate away.

On the other hand, I don't like Schrader valves if I'm using any kind of hand pump because you have to be so careful threading the pump chuck onto the valve stem. For that reason I prefer Presta valves on bicycle tires.

I love Schrader vs. Presta valve discussions because I'm willing to take either side depending on how the wind is blowing. This thread hasn't been a disappointment.
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Old 07-10-11, 11:06 AM
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Originally Posted by Retro Grouch View Post
I'm going to disagree with a whole lot of that.

I don't work in a laboratory but I do know what an air conditioner looks like. Roughly 200 psi line pressure and the valve is expected not to lose ANY refrigerant. I won't tell you what kind of valve, you can look for yourself.

Filling either a bicycle tire or a car tire with an air compressor is MUCH faster and easier using Schrader valves because you don't need to thread on the chuck, just push it against the valve stem and inflate away.

On the other hand, I don't like Schrader valves if I'm using any kind of hand pump because you have to be so careful threading the pump chuck onto the valve stem. For that reason I prefer Presta valves on bicycle tires.

I love Schrader vs. Presta valve discussions because I'm willing to take either side depending on how the wind is blowing. This thread hasn't been a disappointment.
Prathman said 'laboratory equipment', not air conditioners. The pressure in most lab equipment can go orders of magnitude above 200 psi. No one that I work with nor any safety officer worth a damn would allow a pressure vessel in a lab to be pressurized with a Schrader valve and a chuck. Most of the gases you are using in a laboratory setting are either toxic, flammable or both. A small leak of something like arsine, for example, would be deadly.

Air conditioners don't use a Schrader valve either. Not modern ones anyway. Most of the stuff I've seen requires a rather involved gas manifold like this



which uses hard plumbed connections. A quick connect might be used but that isn't the same as a Schrader valve. The gases involved are highly regulated - you have to be certified to do the work.

Why would you need to thread on a chuck for a presta valve if it were used for a car? You don't have to thread it on for bicycles and the pressure involved are much higher. You could just slide it on like you do for a bicycle tube.
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Old 07-10-11, 11:23 AM
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There's only air pressure to overcome with a Schrader valve as well.
valve core has a return spring, yes the pin in the center, when pressed down, opens it.

in the long run It doesn't matter, do what you want ,

you are going to die eventually, any way.
you just wasted some of it, your Life, on this list
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Old 07-10-11, 03:44 PM
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Originally Posted by cyccommute View Post
Why would you need to thread on a chuck for a presta valve if it were used for a car? You don't have to thread it on for bicycles and the pressure involved are much higher. You could just slide it on like you do for a bicycle tube.
OK, so I used a word that you disagree with. I'm thinking you get that a lot. Filling a schrader valve with an air compressor you don't have to slide the chuck onto the valve, just push it against the valve.

Happy now?
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Old 07-11-11, 02:31 AM
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Wonderful discussion, thank you. Now, when some noob posts the same question again in a couple weeks, I can chime in and sound like I know what I'm talking about.
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Old 07-11-11, 02:48 AM
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Works for me, too.
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Old 07-11-11, 05:43 AM
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Originally Posted by prathmann View Post
As stated in my first post, this used to be an issue 40 years ago when the hand pumps for Schrader valves required you to unscrew a hose from the valve and you'd lose some pressure in the process. With the thumblock pump heads that have been common ever since Zefal introduced their HP series pumps this is no longer an issue. Even with 125 psi, 20mm tires the air loss is insignificant - under 1 psi.
Well... I believe it's a bit more complicated than that, but I'm not arguing pro or con between the two styles.

Just out of curiosity, how did you determine that the pressure loss is under 1psi?
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Old 07-11-11, 09:08 AM
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Originally Posted by Retro Grouch View Post
OK, so I used a word that you disagree with. I'm thinking you get that a lot. Filling a schrader valve with an air compressor you don't have to slide the chuck onto the valve, just push it against the valve.

Happy now?
Well, threaded isn't the same as pushed now is it? One involves rotating some kind of threaded nut around a threaded stem and the other is a simple contact. With some exceptions, you don't thread a pump chuck onto a car tire or bicycle tire. Most of the time you just push either chuck onto the tire and start pumping. No threads involved.

I've seen several designs for compressor chucks for use with Presta valves and all of them make better contact with the stem than most chucks for Schrader valves do. If people were to use them on their cars, they'd probably find the system to be superior to the Schrader.
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Old 07-11-11, 12:05 PM
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Originally Posted by cyccommute View Post
Well, threaded isn't the same as pushed now is it? One involves rotating some kind of threaded nut around a threaded stem and the other is a simple contact. With some exceptions, you don't thread a pump chuck onto a car tire or bicycle tire. Most of the time you just push either chuck onto the tire and start pumping. No threads involved.

I've seen several designs for compressor chucks for use with Presta valves and all of them make better contact with the stem than most chucks for Schrader valves do. If people were to use them on their cars, they'd probably find the system to be superior to the Schrader.
OK, so I used a word that you disagree with. I'm thinking you get that a lot. Filling a schrader valve with an air compressor you don't have to slide the chuck onto the valve, just push it against the valve.

Happy now?
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Old 07-11-11, 06:24 PM
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Originally Posted by Retro Grouch View Post
OK, so I used a word that you disagree with. I'm thinking you get that a lot. Filling a schrader valve with an air compressor you don't have to slide the chuck onto the valve, just push it against the valve.

Happy now?
Deja vu.
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Old 07-12-11, 08:09 AM
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Use as a valve cap;
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Old 07-13-11, 08:50 AM
  #25  
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A response from a guy that owns an AC company:

Cyccommute, despite the high tech look of the 134a gauge set and ends in your picture, under the access ports on the system sits a common schrader valves. The end fittings are just a safeguard to insure the proper refrigerent is being used.

Retrogrouch, a little behind the times my friend. Most new a/c systems use 410a.
A normally operating R-410A system with a condensing temperature of 120 degrees and a 45 degree evaporator saturation temperature will have a high side pressure of 418 psig and a low side pressure of 130 psig.

So it would seem the schrader valve can do it's job quite well, this however is not the case, when you remove the schrader valve cap from a 410 a/c system you ,in many cases, get it blown right out of your hand. If it were not for the cap and it's O ring seal the freon would soon be in the wind.

Mike
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