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Noob Question: Valve Stem Lock Nuts



 
 
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  #1  
Old March 11th 04, 02:47 AM
xkred27
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Default Noob Question: Valve Stem Lock Nuts

Three weeks ago I bought my first-ever road bike, a Lemond Tourmelet. Also
bought a floor pump. As of today, both the front and rear tubes on the bike
have failed, both in the same place--at the base of the valve stem.

When I bought the bike, it came with no valve stem lock nuts. I found this
odd, but figured hey, better aerodynamics. These things matter on a road
bike. Because the fit of the new pump was so tight, I found myself really
struggling to get the connector on and off. Then one day I was topping
off. I engaged the connector with the valve stem, pushed down and,
psssssssssssssssst, end of front tube. Took the tube not to the shop where
I bought the bike, but to a sister shop, owned by the same guy. At the
sister shop, they were incredulous that the original shop had sold me a bike
with no locknuts. They gave me two locknuts and a free tube and sent me
home.

Well, today I'd suited up, stretched, and was just turning around to get on
my bike (hadn't so much as touched the tires today) when,
pssssssssssssssssst, the rear tube blew, seemingly because I looked at it
the wrong way. *This* time I went back to the shop that sold me the bike
and said hey, please educate me. These guys said

a) Yeah, that's right, we sold you the bike with no locknuts because you
should never use locknuts unless inflating a totally flat tube. If you're
just topping off, the 90+ PSI already in the tire will minimize the "give"
in the valve stem when you attach the connector.
b) If you leave the locknut on when topping off, you'll
[unintelligible/Nixonian18 minute gap/didn't get what he said/but the gist
of it was you'll blow your tube]

So on the one hand, bike store #1 was aghast that I got no locknuts, and
OTOH store #2 said yeah, that was intentional; don't use locknuts if you're
only topping off a nearly full tire.

I don't know what to think at this point. I toasted the first tube while
topping off without locknut. According to store #2, this was correct
procedure. The second tube fried after numerous top-offs *with* the locknut
on.

And then maybe the locknuts are a red herring. Maybe I killed BOTH tubes as
the result of the frickin' too-tight new pump connector. Was advised on
this by store #2 to connect/disconnect the pump a few dozen times on one of
my toasted tubes in order to loosen up the connector.

So my questions a
a) What's the official word on locknuts and inflating your tires?
b) Do you think my ham-handed use of the new pump was the real culprit in
these failures?

A thousand pardons for my verbositude and a million thanks.

Peter





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  #2  
Old March 11th 04, 04:46 AM
Ken
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Default Noob Question: Valve Stem Lock Nuts

"xkred27" wrote in
:
a) What's the official word on locknuts and inflating your tires?
b) Do you think my ham-handed use of the new pump was the real culprit
in these failures?


I never use tube nuts. Some brands of tubes (e.g., Michelin) don't come with
nuts and they don't thread the valve stems so nuts wouldn't work anyway.

Yes, really poor technique can cause the tube to tear at the valve stem.
  #4  
Old March 11th 04, 12:54 PM
Peter Cole
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Default Noob Question: Valve Stem Lock Nuts

"xkred27" wrote in message
...
Three weeks ago I bought my first-ever road bike, a Lemond Tourmelet. Also
bought a floor pump. As of today, both the front and rear tubes on the bike
have failed, both in the same place--at the base of the valve stem.

When I bought the bike, it came with no valve stem lock nuts.

So my questions a
a) What's the official word on locknuts and inflating your tires?
b) Do you think my ham-handed use of the new pump was the real culprit in
these failures?


Some people find lock nuts helpful, I never have, I just throw them away.
While they can help keep the stem of a totally deflated tube from being pushed
into the tire, so can your thumb, pressing from the other side. If you do use
the nuts, I would caution against tightening them too tight after the tire is
pumped up, since upon deflation they tend to get tighter, and may get too
tight to remove with just fingers (at a time/place where you have no pliers).

Ham-handed pump use can destroy tubes, you have to be careful to "pump into
your fist" -- hold the valve end of the pump in your non-pumping hand, not the
wheel -- let that dangle free. In many cases however, failures around the
valve stem are due to manufacturing problems, and are no fault of the user. If
the sealing grommet on your pump is grabbing the valve too tenaciously
(sometimes a problem with new pumps), you might be able to make it a bit
looser by unscrewing the covering cap (pump) a little.


  #5  
Old March 11th 04, 12:57 PM
Dane Jackson
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Default Noob Question: Valve Stem Lock Nuts

xkred27 wrote:

So my questions a
a) What's the official word on locknuts and inflating your tires?


Eh, not really useful or harmful. I use them most of the time, but
wouldn't get bent out of shape if I didn't have them.

b) Do you think my ham-handed use of the new pump was the real culprit in
these failures?


Possibly some. Though two failures in such a short time says cheap tubes
to me. Are you using a frame pump/mini pump for all these or do you have
a proper floor pump? I ask because maybe you are causing the stem to
separate by not using the frame pump well.

Thinking about conflicting LBS advice, I've become lately astounded
by all the bad advice I get from bike shop people. Whether it's
propagating myths about frame materials, trying to sell me hogwash about
wheels, or simple things like telling me it's not possible to service
this or that part [1]. Many bike shops are crammed with people who really
don't know what they're talking about. When you find a shop filled with
clueful, professional people don't let them go.

[1] I'm planning on picking up some bearings to overhaul one of my
trashed pedals today. Some bozo at the shop swore up and down to me
that that pedal had bushings and we would have to special order them
from Shimano and it would be more expensive than new pedals. Guess
what I found when I opened them up? Stinking dirt standard bearings
with a cup & cone arrangement. :P

--
Dane Jackson - z u v e m b i @ u n i x b i g o t s . o r g
"I was recently on a tour of Latin America, and the only
regret I have is that I didn't study my Latin harder in
school so I could converse with those people."
-Dan Quayle
  #6  
Old March 11th 04, 07:46 PM
David L. Johnson
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Default Noob Question: Valve Stem Lock Nuts

On Thu, 11 Mar 2004 02:47:19 +0000, xkred27 wrote:

So my questions a
a) What's the official word on locknuts and inflating your tires?


Official?? I never use them. Others do. I*manage not to ruin my tubes.
I also never bother with the little plastic valve caps. Others think
those are necessary as well.

b) Do you think my ham-handed use of the new pump was the real culprit
in these failures?


Umm, probably.


--

David L. Johnson

__o | The lottery is a tax on those who fail to understand mathematics.
_`\(,_ |
(_)/ (_) |


  #7  
Old March 12th 04, 12:31 AM
Rick Onanian
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Default Noob Question: Valve Stem Lock Nuts

On Thu, 11 Mar 2004 02:47:19 GMT, "xkred27"
wrote:
Three weeks ago I bought my first-ever road bike, a Lemond Tourmelet. Also


Congrats!

So my questions a
a) What's the official word on locknuts and inflating your tires?


Overtightening the locknut can damage the tube and/or stem. In fact,
damn near anything can damage presta stems; be gentle with them.

I have a locknut loosely on one tube on the bike, just so it's
available if I have to pump from a complete flat. The locknut makes
it more convenient to pump a completely flat tire.

Actually, both of my presta-equipped bikes each have one tube with
an unthreaded stem, so no locknut would fit.

b) Do you think my ham-handed use of the new pump was the real culprit in
these failures?


Probably on the first one, maybe on the second (or, you freaked out
and overtightened the locknut on the second one). Both are probably
manufactured badly.

Try adjustments on the pump head, and try lubricating it with any
handy lube that won't destroy the pump head's seals.

A thousand pardons for my verbositude and a million thanks.


I deserve to be punished with much more verbositude than that,
considering my common neverending posts...the one-liners I post
don't make up for 'em, either.
--
Rick Onanian
  #8  
Old March 14th 04, 04:33 AM
Frederic Briere
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Default Noob Question: Valve Stem Lock Nuts

xkred27 wrote:
a) Yeah, that's right, we sold you the bike with no locknuts because you
should never use locknuts unless inflating a totally flat tube. If you're
just topping off, the 90+ PSI already in the tire will minimize the "give"
in the valve stem when you attach the connector.
b) If you leave the locknut on when topping off, you'll
[unintelligible/Nixonian18 minute gap/didn't get what he said/but the gist
of it was you'll blow your tube]


My, oh my. Allow me to quote Barnett's on this one:

The only function of the valve-retaining nut is to keep the valve from
escaping into the rim when trying to press a pump head onto the valve.
Valve-retaining nuts are also reputed to prevent movement between the
tire and tube under hard braking conditions (and thus prevent the
valve from separating from the tube), but the real cause of this
problem is under-inflation, and nothing will reduce the problem other
than higher inflation pressures.

Feel free to keep/ditch 'em as you wish. Same goes for the plastic
valve cap, which is there to protect the tube when folded in its box.
(Although it nicely keeps the valve nut free of mud and dirt.)

(OTOH, if you ever ride tubulars, Sheldon advises against putting
anything on the valve.)


b) Do you think my ham-handed use of the new pump was the real culprit in
these failures?


Why not take your pump to your LBS, and have them take a look at it?
(IMO, if you have to struggle to use that pump, then something's not
right, and you don't want to wait until you're 50mi from home to find
out what.)


--
Frederic Briere *

= IS NO MO http://www.abacomsucks.com =
  #9  
Old March 14th 04, 02:49 PM
Chris Zacho The Wheelman
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Default Noob Question: Valve Stem Lock Nuts

I use the locknuts on my road tourer (they only weigh a couple of grams)
because it holds the tube in place when mounting the tire and makes it
easier to get the pump on when the tire is low. I loosen the nut after
mounting to push the stem up over the tire beads, then snug it down to
pump up the tube.

On my ATB I use two on each tube. one sits at the bottom of the stem
inside the rim, the other on the outside. The rim is sandwiched between
the two nuts. This is for when I have to run the tire at real low
pressures (sand, for example) to prevent tube creep. And the inner nut
prevents the rim hole from abrading the base of the valve stem

Having a second nut inside the rim also allows drilling the rim out for
Schraeder (auto) valves. Nice if you find you need a new tube and the
only available source is X-mart.

"May you have the wind at your back.
And a really low gear for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner
http://www.geocities.com/czcorner

 




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