Fragile presta valves?

Not sure that I understand. Did the inner tube fail at the base of the
valve stem?

RNK said:

the little sideways movement of the valve actually made the side of the valve tear through the inner tyre!

Were you using a floor pump or a frame pump? With a frame pump you have
to be very careful that your lateral pumping motion doesn't get
transferred to the valve.

http://www.sheldonbrown.com/brandt/presta-nuts.html

Art Harris

teschman said:

Not sure that I understand. Did the inner tube fail at the base of the
valve stem?

Yes, the bit where the valve is fixed to the inner tube rubber.

Art said:

Were you using a floor pump or a frame pump? With a frame pump you >
have
to be very careful that your lateral pumping motion doesn't get
transferred to the valve.

Exactly what I was doing!

Oh well, it spoiled the only day with spare time of this week.. and a
day of perfect cycling weather, too.

Robin.

Per RNK:

Quoted message said:

But no, the little sideways movement of the valve actually made the side
of the valve tear through the inner tyre!

Is this normal?

Not in my experience - and I think I fix more than my share of flats.
--
PeteCresswell

I had a number of these failures and I am an experienced cyclist for
many years. All failures were in the same place, at the base of the
valve stem I used floor pump to inflate, careful not to wiggle the
valve stem while inflating, checked the hole in the rim for any
burrs(there were none) and generally went crazy trying to understand
what was happening. After posting the problem to this group, I found a
number of people had the same problem with the same tubes -- light
weight road tubes by Performance Bicycle. Changed brands and not had a
problem since.
Try searching this group for previous postings by me.

I have only one thing to say.....

Clinchers SUCKKKKKKKKKKKKKKKKKKKKKKKK!!!!!!!!!!!!!!!!!!!! BIG TIME!...

Man put a set of tufo tubular clinchers... your problems will go away for
ever!......

Noname 🙂

"(PeteCresswell)" <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

Per Art Harris:

Quoted message said:

Were you using a floor pump or a frame pump? With a frame pump you
have to be very careful that your lateral pumping motion doesn't get
transferred to the valve.

http://www.sheldonbrown.com/brandt/presta-nuts.html

Which begs the question that's been in the back of my mind for years:
What's wrong with the little 4-inch hoses they used to supply with
frame pumps?

Won't take the pressure? Uncool?

"teschman" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I had a number of these failures and I am an experienced cyclist for
many years. All failures were in the same place, at the base of the
valve stem I used floor pump to inflate, careful not to wiggle the
valve stem while inflating, checked the hole in the rim for any
burrs(there were none) and generally went crazy trying to understand
what was happening. After posting the problem to this group, I found a
number of people had the same problem with the same tubes -- light
weight road tubes by Performance Bicycle. Changed brands and not had a
problem since.
Try searching this group for previous postings by me.

I have had horroble problems with Performance branded tubes also. Like You,
I switched and the problem went away.

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
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Per Art Harris:

Quoted message said:

Were you using a floor pump or a frame pump? With a frame pump you have
to be very careful that your lateral pumping motion doesn't get
transferred to the valve.

http://www.sheldonbrown.com/brandt/presta-nuts.html

Which begs the question that's been in the back of my mind for years: What's
wrong with the little 4-inch hoses they used to supply with frame pumps?

Won't take the pressure? Uncool?
--
PeteCresswell

"RNK" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hello all,

I was just inflating my rear tyre when all of a sudden I heard the
dreaded 'hiss'. The tyre is basically brand new, so I thought the pump
accidentally pushed in the little air release pin in the valve.

But no, the little sideways movement of the valve actually made the side
of the valve tear through the inner tyre!

Is this normal? Bear in mind that these were pretty cheap tyres (I don't
have a lot of money to spare) but shouldn't cheapo tyres be at least a
little less fragile?

This is an all too common manufacturing defect with several brands of inner
tubes of a certain vintage. Try a different brand or newer stock. I've
never experienced the problem with Michelin tubes.

~PB

You think prestas are fragile? In the last month I have had two
Shrader valved tubes self destruct by exploding at the valve stem.
These are Cheng-Shin 20x1.35 tubes. I am switching to prestas tubes
as fast as I can order a few. I have hated Schraders since I first
used prestas in high school and had forgotten some of the reasons why,
but now I remember. They are [censored] for high pressure (about 90 psi).

hhy said:

You think prestas are fragile? In the last month I have had two
Shrader valved tubes self destruct by exploding at the valve stem.
These are Cheng-Shin 20x1.35 tubes. I am switching to prestas tubes
as fast as I can order a few. I have hated Schraders since I first
used prestas in high school and had forgotten some of the reasons why,
but now I remember. They are [censored] for high pressure (about 90 psi).

That makes sense. I know that's how it's supposed to be, but I'll be
damned if my experience isn't backwards. The bike with the prestas runs
at about 110 psi and I have to top it off about every week or so. The
bike with the schrader runs at 90 psi and it's fine for about two weeks.

weird.

--
Paul M. Hobson
Georgia Institute of Technology
..:change the words to numbers
if you want to reply to me:.

In article <[email hidden]>,

Paul Hobson said:

hhy said:

You think prestas are fragile? In the last month I have had two
Shrader valved tubes self destruct by exploding at the valve stem.
These are Cheng-Shin 20x1.35 tubes. I am switching to prestas tubes
as fast as I can order a few. I have hated Schraders since I first
used prestas in high school and had forgotten some of the reasons why,
but now I remember. They are [censored] for high pressure (about 90 psi).

That makes sense. I know that's how it's supposed to be, but I'll be
damned if my experience isn't backwards. The bike with the prestas runs
at about 110 psi and I have to top it off about every week or so. The
bike with the schrader runs at 90 psi and it's fine for about two weeks.

weird.

Volume difference?

--
Michael Press

Paul Hobson said:

Quoted message said:

You think Prestas are fragile? In the last month I have had two
Schrader valved tubes self destruct by exploding at the valve stem.
These are Cheng-Shin 20x1.35 tubes. I am switching to Presta tubes
as fast as I can order a few. I have hated Schraders since I first
used Prestas in high school and had forgotten some of the reasons
why, but now I remember. They are [censored] for high pressure (about 90
psi).

Quoted message said:

That makes sense. I know that's how it's supposed to be, but I'll
be damned if my experience isn't backwards. The bike with the
Prestas runs at about 110 psi and I have to top it off about every
week or so. The bike with the Schrader runs at 90 psi and it's fine
for about two weeks.

Quoted message said:

weird.

Not at all! These valves are not leaking. When pressure drops over
such a long period, it is diffusion through walls of inner tubes, the
thinner the tube and greater its surface area, the faster it will
leak. Besides, Schrader valves are commonly used for industrial use
where they hold more than 200psi. Neither of these valve types are
averse to holding pressures higher than found in bicycling.

A disadvantage of the Presta valve is that it has a conical seal that
jams and prevents it from releasing. For this reason it must usually
be manually forced open before it can be pumped. For this reason,
many bicycle pumps have ruined gauges that were forced beyond their
limit when a Presta valve did not open. In contrast, Schrader valves
have a flat seal that is closed by a spring. The spring force acts
even at low pressures and makes pumping more difficult without a
special valve opener in the pump head.

Stems separating from inner tubes was a manufacturing flaw that was
common about a year or so ago. At that time it was widely attributed
to the knurled stem nut in this forum. This hypothesis can be readily
disproven by screwing the stem nut on by hand as tight as possible and
then inflating the tire to 100psi and noting that the nut is free and
loose, inflation pressure exerting more force than one can apply to
the knurled nut.

Jobst Brandt

Paul said:

I know that's how it's supposed to be, but I'll be
damned if my experience isn't backwards. The bike with the prestas runs
at about 110 psi and I have to top it off about every week or so. The
bike with the schrader runs at 90 psi and it's fine for about two weeks.

I'd expect the biggest pressure drop in the tubes that have the highest
pressure, the thinnest walls, and the lowest volume. My guess would be
that your presta-valved bike 'wins' on all three counts in which case
it's not surprising that it needs pumping more often.

Neither Presta nor Shrader valves should contribute significantly to
loss of air compared to the porosity of the rubber tubes.

Quoted message said:

Stems separating from inner tubes was a manufacturing flaw that was
common about a year or so ago. At that time it was widely attributed
to the knurled stem nut in this forum. This hypothesis can be readily
disproven by screwing the stem nut on by hand as tight as possible and
then inflating the tire to 100psi and noting that the nut is free and
loose, inflation pressure exerting more force than one can apply to
the knurled nut.

I have overtightened a nut by hand when the tyre was partially inflated. It
was not free and loose after fully inflating. But I agree that the main
problem is a manufacturing flaw.

~PB

Quoting (PeteCresswell) <[email hidden]>:

Quoted message said:

Which begs the question that's been in the back of my mind for years: What's
wrong with the little 4-inch hoses they used to supply with frame pumps?

They increase the volume between the end of the piston stroke and the
valve, which decreases the maximum attainable pressure.
--
David Damerell <[email hidden]> Kill the tomato!
Today is Thursday, September.

Quoted message said:

Paul Hobson said:

Quoted message said:

You think Prestas are fragile? In the last month I have had two
Schrader valved tubes self destruct by exploding at the valve stem.
These are Cheng-Shin 20x1.35 tubes. I am switching to Presta tubes
as fast as I can order a few. I have hated Schraders since I first
used Prestas in high school and had forgotten some of the reasons
why, but now I remember. They are [censored] for high pressure (about 90
psi).

Quoted message said:

That makes sense. I know that's how it's supposed to be, but I'll
be damned if my experience isn't backwards. The bike with the
Prestas runs at about 110 psi and I have to top it off about every
week or so. The bike with the Schrader runs at 90 psi and it's fine
for about two weeks.

Quoted message said:

weird.

Not at all! These valves are not leaking. When pressure drops over
such a long period, it is diffusion through walls of inner tubes, the
thinner the tube and greater its surface area, the faster it will
leak. Besides, Schrader valves are commonly used for industrial use
where they hold more than 200psi. Neither of these valve types are
averse to holding pressures higher than found in bicycling.

<snip>

Quoted message said:

Jobst Brandt

Whoa. Thanks for the info. I feel better about the Presta tires now (I
was a little worried).

\\paul
--
Paul M. Hobson
Georgia Institute of Technology
..:change the words to numbers
if you want to reply to me:.

noname said:

I have only one thing to say.....

Clinchers SUCKKKKKKKKKKKKKKKKKKKKKKKK!!!!!!!!!!!!!!!!!!!! BIG TIME!...

Man put a set of tufo tubular clinchers... your problems will go away for
ever!......

Yeah, that'll make fixing flats *so* much easier. Just throw them away
at $50 a pop. What a great solution!

Chalo Colina

LOL.. dude give them a shoot really... u can buy the punture sealant and ur
done... no flats whats so ever hehehe.... trust me.. tubular clincher is so
nice... get one and try it... really...

🙂

"Chalo" <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

noname said:

I have only one thing to say.....

Clinchers SUCKKKKKKKKKKKKKKKKKKKKKKKK!!!!!!!!!!!!!!!!!!!! BIG
TIME!...

Man put a set of tufo tubular clinchers... your problems will go away
for ever!......

Yeah, that'll make fixing flats *so* much easier. Just throw them
away at $50 a pop. What a great solution!

Chalo Colina