DiabloScott

You are absolutely right - the advantage is debatable.
But they exist because tubular tires don't come with Shrader valves, and tubular tires are far superior to clinchers.
Clincher wheels come drilled for presta valves for people who want to pretend they have tubulars.

UniChris

Interesting idea and I may try it, but not sure I can indent my tire far enough.

A week or two back I was trying to figure out why the joint at the base of my thumb hurt so much. Finally figured out it was because I'd misplaced my tire levers and put the tire back on with sheer determination and a random piece of plastic.

squirtdad

FWIW I find the screw on heads, like the Lenzyne better for both presta and scraeder...but the flip lever on a joe blow did ok also

one on my shop pump


the one on my pump I carry on the bike again lenzne

mjac

"And for the record, misspelling Presti is probably a slap to the person that named them IMO."...Good

You completely misunderstand me and perhaps others too but I can not speak for them. I don't mind if anyone uses PrestI or if anyone uses Schrader. I do not fault anyone either way. I am posing a question for my own information because I want to learn, especially about historic practices. "What advantages does using PrestI Valves have?" What are they. One way of getting to this is to provoke debate and even poke a little bit to expose it. Maybe it is integrity of the rim. But I have a hard time buying this. Show me otherwise. My misspelling of PrestI, intentional,unintentional is a way for me to take out my utter frustration on what these valves have caused me. Even if it had been my fault. Which I do not think it was. It is a healthy exercise. But it was all in fun which may have been lost.

mjac

mjac would never fall for such a ploy.

mjac

It wasn't my fault. But I am glad you did what you thought was right, even handedly.

mjac

This is why I started this thread. I want a Lenzne Head,period. I have a pretty good GV Pump with the best flip handle on the pump head I have ever had. But I have to place my thumb directly over the head, which is double sided, to get it over the valve and bury it, then brace that hand against a spoke while flipping the handle with the thumb on the other hand. It can be painful. How does this work. You buy just the head and install it on your pump or do they also make a pump and it would be better to buy the whole pump? Probably just the head. I can look it up, but what is the cost and what is the best option?

I am am curious about one thing, this is how I learn things.nWhy do you use a small hand pump, albeit with a Lenzne head to pump up a tire to 115-120 psi when they have compact Co2 systems that will do it in seconds. I do not understand this from a size perspective and a pumping perspective.

mjac

One rim was drilled for Schrader, one rim was drilled for PrestI. I drilled the PrestI rim for Schrader.( because I hate PrestI) I do not know the throat opening of the rim. I have never measured it. But it accepts my 23-25mm tires. In no way in my mechanical judgement did I compromise the integrity of that rim by drilling it out slightly for Schrader. Not in the least. There is still plenty of metal on the sides of the valve along the rim flat,plenty. Bead seats just fine around the Schrader Valve, in fact I would say easier because the valve isn't sliding up and down.

mjac

Sometimes I can role the last part of the bead on by hand,preferred, sometimes I can't.

mjac

First we must clarify, when you say "Tubular" Tires, do you mean Tubeless?

mjac

Quite the contrary, I am shedding light on long held misbeliefs. It is just that no one can admit their past practices do not hold up to logical scrutiny. You can lead a horse to water but you can't make him take some.

DiabloScott

You're new to this sport, aren't you?

mjac

I am not asking to be swayed and it is not an issue or a big issue for me. I and everyone else can easily ride anything they want. I am posing a direct question in an effort to learn why one selects on or the other. That is, what are the advantages of using PrestI Valves. That is all I want to know. That way I will know what works and why it works. Answer the question. Questioning my motives does not answer the question. Do not avoid the question and look elsewhere for something to comment on. Answer the question. What are the advantages of using PrestI Valves. That is it. Very simple.

mjac

I asked you a question. Answer it. Don't answer a question with another question. What are you referring to? Then I can answer properly.

DiabloScott

The answer to your question is "No - I didn't mean tubeless". and by the way, your ability to troll us will improve when you can talk the talk.


FNG

mjac

40's? What are you riding?

mjac

Girly - PrestI...That simple. Just making fun. You have to have a special valve that serves no purpose. At least no one has been able to provide one.

Now that makes sense. Tubular Tires all came with PrestI Valves and when Clinchers came out they could use there pumps that they had for there Tubulars and wanted something familiar. But it was just a carry over from Tubulars that made people feel racy. That is what I am talking about. Something carried over with no real purpose and people just keep on doing it and don't know why. Just because that is how it was done in the past even though it was an entirely different tire. I do not agree with that.

I do not know the proper spelling,I just learned of this, but the "Lezine" head sounds like the only way to go. You are the second person to bring it up.(he spelled it differently I believe) I assume you buy just the head and install it on your existing pump. I can look it up but do you know the general costs? That screw on head would be flawless. I have a descent pump with a descent head on it but flip levers have always given me trouble. They actually hurt my hand. This thing should work like a dream and solve that problem completely. The guy posted a picture of it and it really looks good. That flipping of the lever is the worst thing about pumping up tires. Got to get one...Thanks,mjac

mjac

You make an accusation that is unsupported and unfounded. I have not trolled anyone, I never have and I never will. It is against my nature. I am posing a very simple question. What are the advantages of a PrestI Valve, which no one seems to want to answer. So I am going to find out why. That is it. If that is trolling then your definition of trolling is different then my definition of trolling and I resent it. Until this is resolved we have no basis for discussion. I do not falsely accuse anyone of anything and no one falsely accuses me of anything. Trust me.

desconhecido 

Lezyne is the spelling and the chuck that I bought with a hose from Amazon is about $19. The have small pump that will mount on bottle bosses, I believe, with the double ended hose for about $25. One thing you need to know about the Lezyne double ended chuck. It has a pressure release valve for use with presta valves only. If you push it while a shrader valve is connected, it will likely release air as the shrader valve, because of its inferior design, cannot be inflated just with air pressure alone. The spring loaded valve must be depressed. Isn't that depressing?

I get that you don't like presta valves. I've heard that when God made shrader valves he realized right away what a terrible mistake he had made but rather than fix it, he decided it would be easier to just make people that liked them.

As for your attempt to insult people for fun by implying that presta valves are for sissies, it isn't very funny and it's not really effective as an insult. I don't know why you do it. But, I don't know why you like shrader valves either.

cyccommute 

If you are losing all the air while engaging or disengaging the pump head from a Presta valve, you are doing something very wrong. The pump chuck should slide over the valve without even releasing air. When you disengage the pump, you should just pull it off.

The advantages of the Presta valve is that it is a one way check valve. Any pressure in the hose over the internal pressure opens the valve and lets air into the tube. When the pressure in the hose equals (or falls below) the pressure in the tube, the Presta valve closes. Rinse and repeat as necessary.

Schrader valves, on the other hand, have to be held open throughout the pumping process. If air is leaking out of the hose or chuck (a common occurrence), there is air leaking from the tube. You could make them work like a Presta valve but the “cracking pressure” or the pressure needed to open the valve is much higher in the Schrader valve. It’s on the order of 25 psi. In other words, to open the valve requires 25 psi higher than what is in the tube to open it.

The Lezyne head is the worst head for Presta. The whole point of a Presta valve and a Presta chuck is to not have to screw it on. The second worst design is the flip lever head. It’s not needed for a Presta. The chuck slips onto the valve and is held by friction. The best chuck for Presta is a Silca chuck or cheaper variant. It’s a simple mechanism that is highly effect and avoids the problem of pushing down on the pin of the Presta valve.

Because carbon dioxide canisters are single use. Have 2 flats and you are walking home. Pumps never run out of air...as long as you can breathe, they work. If you can’t breathe, you have bigger fish to fry.

Additionally, carbon dioxide diffuses from the tire very quickly. They can experience significant pressure loss in 24 hours or less. They are for short term use.

Gresp15C

What I've heard is that the smaller hole is preferable for very narrow rims. It's also possible that with care, you lose less pressure as you remove the pump head, which would be a potential issue with narrow and high-pressure tires.

I've personally had Presta tubes fail at the base of the stem, but have never had a Schrader tube fail in that way. Others have had better results with Presta tubes. Reliability is a hard thing to pin down because it can depend on user technique, or on the condition of other parts such as the hole in the rim itself and the quality of the pump head. A burr in the hole could bode ill for tubes.. Likewise for a futzy pump head. On the other hand, a design that's more sensitive to user error may be regarded by some people as a less reliable or more delicate design. The distinction may factor into the choice of parts for bikes that are used in less well controlled environments, such as by beginners, or in shared use.

A little bit of your own personal spittle on the pump head might help. Inspecting the inside of the valve hole is advisable.

Personally, if I had rims drilled for Schrader and was able to achieve satisfactory pressure, I wouldn't see a reason to use a Presta tube. If a bike was made that way, it probably has wider and relatively lower pressure tires anyway. I live with having both kinds of valves in the family fleet.

With many kinds of bike components, history has given us multiple standards with no clear winner, and extensive anecdotal advice about which one is preferable. Making your own choice in the face of conflicting advice is part of the fun.

mjac

Right now I have a pretty good pump called the GV but it is of the type you say is second worst design for PrestI. It has a barrel head with a Schrader head on one side and a PrestI head on the opposite side actuated by a lever. It is a pretty good design but the lever is hard to engage. When I put the PrestI head over the valve I have my thumb over the top of it(the Schrader end) to shove it on. When I shove it down air pours out of the Schrader end where my thumb is. Usually letting all the air out of the tire. So I assume the same thing is happening when I release it. Everyone says no. I don't know. I do not have these issues with the Schrader. Hence the frustration. I was told the Lezyne Head works well with PrestI and Schrader. You say no. That is why I am here. To find out. I am not using PrestI valves, I do not like them. I do not like the lever on the pump head. So I would like to use the Lezyne on the Schrader Valves.

I thought the Co2 was double use. I have to rethink this. I did feel there might be an issue with it being a different gas. I just did not know what it was. Turns out it is a lighter gas and dissipates. So it has draw backs. I did not know any of this and went out and got an inexpensive one because it was compact. Live and learn.

mjac

That is reasonable enough, From the looks of it I thought it might be a high ticket item. Some people say they don't work well with PrestI some say they do. But I am not going to use it on PrestI Valves so it does not matter. I like the screw on fitting, I do not like the levers that have been on all my pumps. The Lezyne looks good in all aspects.

Schrader inferior? PrestI week base. Schrader strong base. That is it. That simple. No one, I mean no one, has told me one advantage PrestI has over Schrader. That is all I am asking. What advantages does PrestI have. I know of one the Schrader has.

Lets make one one thing perfectly clear. I am not insulting anyone and never will. I am not implying anything about people who use PrestI Valves. That is an inference other people have made. It does not matter to me what valve people use, that is their preference and I have no right to question that. I am making fun of the valve out of the utter frustration of lost rides,time and expense because of them out of frustration in a fun way. Little PrestIs. I don't like them. So I make fun of them. Not the people who use them and they can come on and defend their use of them.

cyccommute 

It sounds like you have a pump chuck like this one.



The issue you seem to be having is that you are jamming the head on to the Presta valve as far as it will go. You don't need to do that. All you need to do is to clear the threads for the valve cap and throw the thumb lock. The valve shouldn't come in contact with anything inside the chuck. It doesn't need to and it's detrimental to keeping air in the tube. Let the valve work like it is supposed to...as a check valve. No need to hold it open.

The problem with the Lezyne (and many other pump chuck designs) is that it sacrifices the simplicity of the Presta valve for no reason. The Lezyne head needs to be screwed into place. It's fiddly. "Smart heads" (which aren't, really), have a soft pin that pushes on the Presta valve which is also not needed. The Silca chuck simply slips on and slips off. There's nothing inside the head that even touches the pin on the Presta valve. Slide it on and pump the tire. Slide it off when done.

The Silca is a bit expensive...$40!!!!...but there are others that work just as well without costing an arm, leg and first born child. The SKS adapter



is usually less than $10 and works as well as the Silca without the name.

Generally, a 16 oz cartridge is enough of only one tire and maybe a little bit...depends on the volume and pressure of the tire. If there is any left over, it will probably leak out before you can use it again. The seals on the head aren't all that good.

Carbon dioxide is actually the heaviest of all the naturally occurring atmospheric gases. It's also a huge molecule in terms of the bond lengths. Oxygen, nitrogen and water are all fairly small in comparison. The issue with it diffusing out of rubber isn't the size but the way it interacts with the rubber. Oxygen, nitrogen and water vapor...in order of rapidity...diffuse through the rubber via small channels and holes in the rubber and are rather slow to do it. Water can't really get out of the rubber at all because of it's molecular shape and the electron configuration.

Carbon dioxide, on the other hand, doesn't just diffuse through the rubber, it actually dissolves through the rubber. It doesn't weaken the rubber but it makes a kind of solid/gas solution and zips right through. It has a lot to do with the electron configuration and the shape of the CO2 molecule.

All of the gases with the exception of water (which really isn't a "gas") will diffuse from the high pressure system in the tire to the lower pressure outside the tire. CO2 just does it better than the other gases.

Retro Grouch 

The question was rhetorical. The post was really an observation.