Bicycle Mechanics - presta valves - how do the little 'valve closer' thingies get broken?

presta valves - how do the little 'valve closer' thingies get broken?

i mean

a. it takes zero force to open or close them

b. when they are on the wheel, nothing touches them

c. when in a pump nozzle, nothing NEEDS to touch them - air pressure makes them open
it isn;t like schrader that needs to be pressed to open

d. even when in a pump nozzle, if something WERE touching them, they wouldn;t close, and the air would come right back and push the pump handle out.. so you would think nothing ever touches the things..

e. yet - about half of mine are cocked over to one side, and 2-3 times a year, one of them will fall out after pumping and the tube is toast

so what makes them bend, and then what makes them break?

i do tend to never throw them out til the valve breaks or there is a hole at the valve stem base
so maybe mine are old but still..

i don;t use caps usually
and i don;t close them very hard
wtf

wle

They get bent when removing the pump head if you have to wiggle it to get it off.

They get bent when removing the pump head if you have to wiggle it to get it off.

hm
have to think about that
usually i just knock the pump off straight in line with stem..

i was wondering if maybe when you lock the nozzle on, with the lever, that may be forcing something..?


wle

I think you are not "knocking" the pump head off as straight as you think. Those valve stems are pretty fragile.

I think you are not "knocking" the pump head off as straight as you think. Those valve stems are pretty fragile.

yet if you try to straighten one back out, it;s practically impossible..

i believe you, but why is that?

wle

They get bent when removing the pump head if you have to wiggle it to get it off.

+1

I have found that often riders who has recently moved from an all schrader valve world to using presta valves tend to "rock" the pump head back and forth to remove it, which bends the stem. After you teach them to rotate the tire so that the valve is at the top of the wheels rotation, and then to "pop" the pump head straight off the valve with a slight downward tap on the pump near the pump head, they never bend one again.

When you leave the Cap off.. too..

I've used Silca's bell shaped pump head. for decades..
NB the gasket lip goes on the narrow unthreaded band,
between the 2 differently threaded portions

presta valves - how do the little 'valve closer' thingies get broken?

Because it's a poor design that does not take real world handling into account.

but it is what is, if it really bothers you, ream the rim hole bigger
and use Schrader stem tubes instead.

30 years on, I've had no problems, as described..
just with bonding of the other end into the rubber allowing air loss..

I broke off one of those valve thingies also. I believe it was from over tightening but who knows. Now I'm careful to barely tighten and in pulling off the nozzle. Better results now post thingy episode.

Drill to 11/32" for schrader if you can. Consider rim width/strength and depth of rim 'V' in relation to the schrader stem length you can get. bk

but it is what is, if it really bothers you, ream the rim hole bigger
and use Schrader stem tubes instead.
.

thanks but no thanks
just wondering the mechanism
wle

When you leave the Cap off.. too..


--what are you trying to say?
==wle

older inferior technology

older inferior technology
what would be better?
[[not schrader..]]
wle

To the OP....

If you loosen the valve "thingy" BEFORE inflating...
and re-tighten AFTER inflating...

Wouldn't you notice when they get bent?

To the OP....

If you loosen the valve "thingy" BEFORE inflating...
and re-tighten AFTER inflating...

Wouldn't you notice when they get bent?

theoretically, yes
i will start watching better
some tubes i recycle from unknown sources
they may be bent when i get them

also, next time i get an unrepairable tube with a good valve, i will try the 'wiggle pump head' theory out

wle

Story:

On a century last year I got a flat at the bottom of a long hill before the rest stop at the top. The presta stem nut broke off when I removed the pump but the air in the tire pretty much stayed in there - a little soft but ridable. It was odd to see a stem with nothing plugging the end. I made it up the hill where the sponsor mechanic fixed me up. Said he'd never seen anything like it either and when we tried to pump it up we realized that air pressure was holding the valve in place from the inside, but nothing was holding it in place when air was coming from the pump, so after one stroke the valve fell out inside the tube and the tire went totally flat.

I think it's in how stright you hold the pump when detaching it from the tube. I got mine a little crooked on Saturday, but I was able to bend the thing back.

Story:

On a century last year I got a flat at the bottom of a long hill before the rest stop at the top. The presta stem nut broke off when I removed the pump but the air in the tire pretty much stayed in there - a little soft but ridable. It was odd to see a stem with nothing plugging the end. I made it up the hill where the sponsor mechanic fixed me up. Said he'd never seen anything like it either and when we tried to pump it up we realized that air pressure was holding the valve in place from the inside, but nothing was holding it in place when air was coming from the pump, so after one stroke the valve fell out inside the tube and the tire went totally flat.

I had that happen to me. I rode the bike that way for several months before the valve failed altogether. I carried a spare just in case and eventually had to put it on.

I had that happen to me. I rode the bike that way for several months before the valve failed altogether. I carried a spare just in case and eventually had to put it on.

Several months without needing to top off the pressure?

Presta valves are more efficient at holding higher air pressures (80psi +) than Schraeder Valves are. For as long as the Schraeder valve
has been around, so too has the Presta valve. Just a different design is all.

Screw the brass plug down snugly, put on the cap, and don't rock the pump head when you take it off the valve. That's what causes them to break.

Alan :speedy:

Several months without needing to top off the pressure?

Several months including topping off the pressure every once in a while. Sometimes the valve wouldn't work and all the air would come out; I would pump them back up and the valve would work the next time. Eventually.... it didn't work.

I'm 48 years old and a lifetime rider. I've had presta valves on my bikes since 1980 and have never, ever run into this issue. What ARE you people doing?

Actually, two possibilities: one, the older friction chucks we used like the ones made by Silca didn't touch the end of the valve. You had to "burp" the valve to break the seal, then air was pushed past the seal to inflate the tire. You pulled 'em straight off, no problem. But now, so many pumps have dual heads which actually, in some cases, contact the tiny little brass nut. Any wiggling during removal and you get bent, then broken stems.

A little care works wonders here.

Presta valves are more efficient at holding higher air pressures (80psi +) than Schraeder Valves are.

Schrader valves hold pressure just fine at high psi.

Because it's a poor design that does not take real world handling into account.


Schrader valves hold pressure just fine at high psi.

Presta valves are hard on the tire pumps coupler innards to, at least the threaded presta valves. I have wheels with both presta and schrader valves and they both hold high pressure just fine.

I'm 48 years old and a lifetime rider. I've had presta valves on my bikes since 1980 and have never, ever run into this issue. What ARE you people doing?...A little care works wonders here.

I've been dealing with the skinny tires and the presta valves for around 5 years and have never broken the valve stem (I don't think I've even bent one) and that was while using several "cheapish" floor and mini pumps (I have now upgraded to a Lezyne floor and Lezyne mini pump)...I have torn a hole in the bottom of the presta stem (where it connects to the tube) once or twice while pumping...I see I made it to the beginning of the shrader/presta wars ...I've got a bike with schrader on the back wheel and presta on the front wheel. I think the schrader valve is more "robust/tougher" than the presta, but if you take a little extra precautions with the presta it is quite functional (proper holding/pumping technique is crucial, especially while using a mini pump (the ones that don't have a hose, but connect directly, pump-head to valve)).