Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 04-15-12, 06:36 AM   #1
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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
wle is offline   Reply With Quote
Old 04-15-12, 06:57 AM   #2
byte_speed
Roadkill
 
byte_speed's Avatar
 
Join Date: Sep 2004
Location: East Tennessee
Bikes: 2002 Lightspeed Classic; 2010 Pedalforce RS
Posts: 857
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
They get bent when removing the pump head if you have to wiggle it to get it off.
byte_speed is offline   Reply With Quote
Old 04-15-12, 07:07 AM   #3
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by byte_speed View Post
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
wle is offline   Reply With Quote
Old 04-15-12, 07:12 AM   #4
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Posts: 4,488
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
I think you are not "knocking" the pump head off as straight as you think. Those valve stems are pretty fragile.
dsbrantjr is offline   Reply With Quote
Old 04-15-12, 07:13 AM   #5
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by dsbrantjr View Post
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
wle is offline   Reply With Quote
Old 04-15-12, 07:22 AM   #6
Stealthammer
Still spinnin'.....
 
Stealthammer's Avatar
 
Join Date: May 2009
Location: Whitestown, IN
Bikes: Fisher Opie freeride/urban assault MTB, Redline Monocog 29er MTB, Serrota T-Max Commuter, Klein Rascal SS, Salsa Campion Road bike, Pake Rum Runner FG/SS Road bike, Cannondale Synapse Road bike, Santana Arriva Road Tandem, and others....
Posts: 1,208
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by byte_speed View Post
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.
Stealthammer is offline   Reply With Quote
Old 04-15-12, 09:48 AM   #7
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,796
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
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
fietsbob is online now   Reply With Quote
Old 04-15-12, 10:00 AM   #8
Doohickie 
You gonna eat that?
 
Doohickie's Avatar
 
Join Date: Sep 2008
Location: Fort Worth, Texas Church of Hopeful Uncertainty
Bikes: 1966 Raleigh DL-1 Tourist, 1973 Schwinn Varsity, 1983 Raleigh Marathon, 1994 Nishiki Sport XRS
Posts: 14,320
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by wle View Post
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.
__________________
I stop for people / whose right of way I honor / but not for no one.



Originally Posted by bragi "However, it's never a good idea to overgeneralize."
Doohickie is offline   Reply With Quote
Old 04-15-12, 12:07 PM   #9
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,796
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
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..

Last edited by fietsbob; 04-15-12 at 01:53 PM.
fietsbob is online now   Reply With Quote
Old 04-15-12, 01:46 PM   #10
berner
Senior Member
 
Join Date: May 2010
Location: Bristol, R. I.
Bikes: Specialized Secteur, old Peugeot
Posts: 2,254
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
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.
berner is offline   Reply With Quote
Old 04-15-12, 03:14 PM   #11
bkaapcke
Senior Member
 
Join Date: Jul 2005
Bikes:
Posts: 3,222
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
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
bkaapcke is offline   Reply With Quote
Old 04-15-12, 03:17 PM   #12
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by fietsbob View Post
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
wle is offline   Reply With Quote
Old 04-15-12, 03:18 PM   #13
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by fietsbob View Post
When you leave the Cap off.. too..
--what are you trying to say?
==wle
wle is offline   Reply With Quote
Old 04-16-12, 01:00 PM   #14
rumrunn6
Senior Member
 
rumrunn6's Avatar
 
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Bikes: Bottecchia Sprint
Posts: 14,035
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
older inferior technology
rumrunn6 is offline   Reply With Quote
Old 04-16-12, 01:14 PM   #15
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by rumrunn6 View Post
older inferior technology
what would be better?
[[not schrader..]]
wle
wle is offline   Reply With Quote
Old 04-16-12, 01:25 PM   #16
Hendo252 
Senior Member
 
Join Date: Feb 2012
Location: SoCal
Bikes: 1983 Trek 620, 2010 Roubaix
Posts: 371
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
To the OP....

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

Wouldn't you notice when they get bent?
Hendo252 is offline   Reply With Quote
Old 04-16-12, 01:28 PM   #17
wle
Senior Member
Thread Starter
 
wle's Avatar
 
Join Date: Jan 2004
Location: atlanta ga
Bikes: road: 1999 GT road:40Kmi+ // 2001 fuji finest AL:9Kmi+//1991 schwinn paramount ODG:0.1Kmi+
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Hendo252 View Post
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
wle is offline   Reply With Quote
Old 04-16-12, 01:29 PM   #18
DiabloScott
It's MY mountain
 
DiabloScott's Avatar
 
Join Date: Sep 2006
Location: Mt.Diablo
Bikes:
Posts: 6,703
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
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.
DiabloScott is offline   Reply With Quote
Old 04-16-12, 01:38 PM   #19
DaveZ
DeadheadDave
 
Join Date: Sep 2008
Location: Sacramento
Bikes: 1 Trek road bike, 1 Nishiki road bike (old), 1 Cannondale
Posts: 64
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
DaveZ is offline   Reply With Quote
Old 04-16-12, 01:52 PM   #20
Doohickie 
You gonna eat that?
 
Doohickie's Avatar
 
Join Date: Sep 2008
Location: Fort Worth, Texas Church of Hopeful Uncertainty
Bikes: 1966 Raleigh DL-1 Tourist, 1973 Schwinn Varsity, 1983 Raleigh Marathon, 1994 Nishiki Sport XRS
Posts: 14,320
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by DiabloScott View Post
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 stop for people / whose right of way I honor / but not for no one.



Originally Posted by bragi "However, it's never a good idea to overgeneralize."
Doohickie is offline   Reply With Quote
Old 04-16-12, 02:27 PM   #21
DiabloScott
It's MY mountain
 
DiabloScott's Avatar
 
Join Date: Sep 2006
Location: Mt.Diablo
Bikes:
Posts: 6,703
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Quote:
Originally Posted by Doohickie View Post
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?
DiabloScott is offline   Reply With Quote
Old 04-16-12, 02:42 PM   #22
oldskoolwrench
自転車整備士
 
oldskoolwrench's Avatar
 
Join Date: Apr 2012
Location: Denver, Colorado USA
Bikes: '86 Moots Mountaineer, '94 Salsa Ala Carte, '94 S-Works FSR, 1983 Trek 600 & 620
Posts: 898
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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
oldskoolwrench is offline   Reply With Quote
Old 04-16-12, 03:58 PM   #23
Doohickie 
You gonna eat that?
 
Doohickie's Avatar
 
Join Date: Sep 2008
Location: Fort Worth, Texas Church of Hopeful Uncertainty
Bikes: 1966 Raleigh DL-1 Tourist, 1973 Schwinn Varsity, 1983 Raleigh Marathon, 1994 Nishiki Sport XRS
Posts: 14,320
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by DiabloScott View Post
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 stop for people / whose right of way I honor / but not for no one.



Originally Posted by bragi "However, it's never a good idea to overgeneralize."
Doohickie is offline   Reply With Quote
Old 04-16-12, 04:28 PM   #24
BikeWise1
30 YR Wrench
 
BikeWise1's Avatar
 
Join Date: Aug 2005
Location: Oxford, OH
Bikes: Waterford R-33, Madone 6.5, Trek 520
Posts: 2,006
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
BikeWise1 is offline   Reply With Quote
Old 04-17-12, 07:24 PM   #25
sk0tt
Senior Member
 
sk0tt's Avatar
 
Join Date: Jul 2007
Location: Perth, Western Australia
Bikes:
Posts: 336
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by oldskoolwrench View Post
Presta valves are more efficient at holding higher air pressures (80psi +) than Schraeder Valves are.
Schrader valves hold pressure just fine at high psi.
sk0tt is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 09:54 PM.