Ever seen a flat like this?



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T

Tilman

Guest
Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
3/4" away from the valve. I have ruled out the following causes:

1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
of the tube.

2) Bad rimtape: No spoke nipples in the area.

3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.

4) Burr at the valve hole: The holes are too far away from the valve stem.

Tube was a longstem tube. Rim a Mavic Ksyrium.

Any idea what could be causing this?

Tilman.
 
J

Jim

Guest
OK heres a guess; the nut on the valve too tight, drawing the tube into the hole it the rim, rim
cuts tube. If your rim is a box section design, doesn¹t the stem go through 2 holes? The nut would
draw the stem through The first, taped hole just enough to allow the tube to expand into the hollow
core and be exposed to the underside of the hole?

Seems reasonable to me

jim

"Tilman" <[email protected]> wrote:

> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve. I have ruled out the following causes:
>
> 1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
> of the tube.
>
> 2) Bad rimtape: No spoke nipples in the area.
>
> 3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.
>
> 4) Burr at the valve hole: The holes are too far away from the valve stem.
>
> Tube was a longstem tube. Rim a Mavic Ksyrium.
>
> Any idea what could be causing this?
>
> Tilman.

jim

[email protected]
 
J

Jim

Guest
BTW I did see in your original post that you thought the holes were too far away from the stem hole,
but, if you have a box section rim, 3/4 of an inch might not be too far away.

jim


"Tilman" <[email protected]> wrote:

> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve. I have ruled out the following causes:
>
> 1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
> of the tube.
>
> 2) Bad rimtape: No spoke nipples in the area.
>
> 3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.
>
> 4) Burr at the valve hole: The holes are too far away from the valve stem.
>
> Tube was a longstem tube. Rim a Mavic Ksyrium.
>
> Any idea what could be causing this?
>
> Tilman.

jim

[email protected]
 
D

David Kunz

Guest
Tilman wrote:
> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve. I have ruled out the following causes:
>
> 1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
> of the tube.
>
> 2) Bad rimtape: No spoke nipples in the area.
>
> 3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.
>
> 4) Burr at the valve hole: The holes are too far away from the valve stem.
>
> Tube was a longstem tube. Rim a Mavic Ksyrium.
>
> Any idea what could be causing this?
>
> Tilman.

Try another brand tube. I had 3 Michlin (I think) tubes fail in a similar manner right in a row. No
other brand tube did this before or after. These were long stem. I've since gotten rid of the rim
since getting long stem presta tubes was a PITA and working with the presta valve extensions was
even worse...

David
 
R

Res09c5t

Guest
Hi, This isn't likely to be it but have you checked your tires for problems? I had a series of
flats last year that I thought were snakebites but turned out to be the wire bead poking through
on the inside of the tire. It stayed pretty flat so it wouldn'y puncture the tube immediately but
it would rub against the tube and cause a flat after 10 or 20 miles. This isn't likely to happen
to both sides at once and the location may not be right but thought it might be a thought starter
for you. Lyle

"Tilman" <[email protected]> wrote in message
news:[email protected]...
> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve. I have ruled out the following causes:
 
D

Doug Milliken

Guest
I've had flats like this when the valve didn't seat properly in the valve hole. This left "voids"
between the rim and the tube on either side of the valve. When inflated the tube balloned
(stretched) into these areas, then punctured in it's own good time (usually when not riding).

In my case, one fix was to build up "wedges" of rim tape on either side of the valve hole, to fill
the void. The real fix was to get a tube that fit properly in the drop center of the rim.

On 25 Apr 2003, Tilman wrote:

> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve. I have ruled out the following causes:
>
> 1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
> of the tube.
>
> 2) Bad rimtape: No spoke nipples in the area.
>
> 3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.
>
> 4) Burr at the valve hole: The holes are too far away from the valve stem.
>
> Tube was a longstem tube. Rim a Mavic Ksyrium.
>
> Any idea what could be causing this?
>
> Tilman.
 
P

Pete Biggs

Guest
Tilman wrote:
> Recently I had a string of flats that looked very suspicious. Turns out there were two holes close
> to the valve stem. Both holes were inline with the valve stem on either side of the valve roughly
> 3/4" away from the valve.

I've had the same thing happen several times with Vredestein "Race" tubes, except the holes were
closer to the valve. I've never experienced it with other tubes used with the same rim and rim tape.
I put it down to the tube's valve reinforcement pad being a too-small disc instead of the usual
large oval that other brands use.

~PB
 
T

Tilman

Guest
Thank you, this pointed me in the right direction: Turns out that I pushed the valve stem up in
order to seat the tire properly, but inflating the tube never pushed the valve stem back down. With
the long stem tubes, it is hard to tell how much valve stem is supposed to show. Now as I pumped up,
the tube ballooned around the valve stem. Needles to say, once you a hit a small pump right where
the valve is, the tube gets squished into the rim hole. I actually reproduced this at home, just
purposly not seating the stem properly and then pushing it in after inflating - the holes match
exactly the ones on my other tubes.

Doug Milliken <[email protected]> wrote in message
news:<[email protected]>...
> I've had flats like this when the valve didn't seat properly in the valve hole. This left "voids"
> between the rim and the tube on either side of the valve. When inflated the tube balloned
> (stretched) into these areas, then punctured in it's own good time (usually when not riding).
>
> In my case, one fix was to build up "wedges" of rim tape on either side of the valve hole, to fill
> the void. The real fix was to get a tube that fit properly in the drop center of the rim.
>
>
> On 25 Apr 2003, Tilman wrote:
>
> > Recently I had a string of flats that looked very suspicious. Turns out there were two holes
> > close to the valve stem. Both holes were inline with the valve stem on either side of the valve
> > roughly 3/4" away from the valve. I have ruled out the following causes:
> >
> > 1) Snakebite: Holes in this case would not be inline but rather on either side of the centerline
> > of the tube.
> >
> > 2) Bad rimtape: No spoke nipples in the area.
> >
> > 3) Bad tube: Tried a few tubes, failure never at the seam or any other manufacturing relict.
> >
> > 4) Burr at the valve hole: The holes are too far away from the valve stem.
> >
> > Tube was a longstem tube. Rim a Mavic Ksyrium.
> >
> > Any idea what could be causing this?
> >
> > Tilman.
> >
 
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