odd flat wheel

PhilD wrote:
............

Quoted message said:

That's when I noticed something I've not come across before. In the
area of the patch there's a sort-of "unbulge". That is, everything
fits nicely all round except where the patch is, which hasn't inflated
as much. It appears that the patch hasn't stretched as much as it
chould (if at all!) on filling the tube with air.

I've seen unbulged bits of patched tubes before when the tube is inflated
outside of the tyre, but I always assumed they would fill out once inside
the tyre and fully pumped up, and they seem to with mine.

~PB

In article <[email hidden]>

PhilD said:

I recently suffered a puncture caused by a long sliver of glass. Not
one of those "pump it up every few minutes and I'll make it home" type
punctures, but a dramatic pssssshhhhhhht, won't hold any pressure at
all job. 30 minutes brisk walk home at dusk.

Well, I've dealt with punctures before. Locate the hole, patch and
reassemble. Done it loads of times. This one was different.

To start with, on reinflating I noticed the inner tube trying to come
out from under the tyre. Okay, deflate (there was only a small amount
of air in the tube), refit, try again. This worked. Put a bit more
pressure in, jiggle the wheel/tyre around a bit to make sure
everything's seated properly all round. Finally, eventually, reinflate
to full pressure.

That's when I noticed something I've not come across before. In the
area of the patch there's a sort-of "unbulge". That is, everything
fits nicely all round except where the patch is, which hasn't inflated
as much. It appears that the patch hasn't stretched as much as it
chould (if at all!) on filling the tube with air.

That's unlikely to be caused by the tube (the bit without the patch
would stretch to compensate, as it's the tyre carcass that determines
the shape when fully inflated) - it sounds as if the tyre isn't properly
seated on the rim, which could cause both the "tube trying to escape"
phenomenon on the bit where the bead is sitting too high, and the flat
spot where the bead is sitting too low. It could be caused by the
rimtape, tube or valve base being trapped between the tyre bead and the
rim.

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

Quoted message said:

I recently suffered a puncture caused by a long sliver of glass. Not

Quoted message said:

one of those "pump it up every few minutes and I'll make it home" type

Quoted message said:

punctures, but a dramatic pssssshhhhhhht, won't hold any pressure at

Quoted message said:

all job. 30 minutes brisk walk home at dusk.

Quoted message said:

This reminds me of an odd puncture last year. Twas a three inch wood screw.
Went through tyre, then tube and out through the valve!

Amazing! and the odd thing was three bangs! The three bangs bothered me as I
put in a new tube, pumped up and rode home.

When you get home after such an event you do the proper thing and go fetch
the track pump to put some 'proper' pressure in the tyre.

In the morning tyre is flat!

Odd! (Three bangs)

Remove tube and inspect for puncture. Not really a puncture more a
manufacturing defect in the tyre. Sort of circular shape a few mm in dia.

Another tube. Pump up and off to work.

Bang!#

Another defective tube! Sort of circular in .. Hang on. (Three bangs) The
circle matches the spoke hole. And look, another one.

Explanation (I think) Tyre is city jet pumped to 85 psi. Screw deflates tyre
almost instantly and air pressurises gap between tube and rim. Plastic rim
tape cant take the pressure and blows a small circular hole at the spoke.
Rim is sharp and jagged and cuts the new tube if the pressure is high
enough.

Three bangs. One for the tube. One for the first rim tape hole. One for the
second.

Brian