"Ace" wrote in message
...
On Mon, 14 Sep 2009 08:18:07 +0100, "Doki" wrote:

I keep getting punctures on my mountain bike, where the Schraeder valve
has
been pulled off the tube. Clearly, the tyre is rotating slightly on the
rim
under braking, and pulling the tube along with it, which eventually rips
the
valve off.

Tyres are 2.25" Panaracers, running at a fairly low pressure, and are well
within the maximum specs for the rim (I think the max is 2.5"). I don't
want
to increase pressure, unless I really have to.

Any ideas on possible remedies? I don't really want to superglue the tyres
to the rim... The tyres are also about 4 years old, if that makes any
odds.

Haven't seen these for years, and TBH I'm not even certain they were
ever made for pedal cycles, but some trials motorbikes, running very
low pressures in tubed tyres, would have a retaining device bolted
through the rim. This would be a shaped flat plate, sized to fit
between the beads of the tyre, but within the rim, and would be
securely tightened from the outside.

Not the best description, so I'll try some ASCII art instead.

| | ---- Tyre
| plate |
\ | /
\ \ V / / ---- Rim
\ \============= / /
\ \ || / /
\______||______/
[||]

Not sure that helps, nor where you would find such a thing, but
hopefully you'll get the idea.

Yep, I know what you mean. Never heard of them being available for pushbikes
though - I suspect most racers use higher pressures and ride full
suspension, or go tubeless, so there's no real market for something like
that (extra weight).