more 29-er flat problems

Having established on a different thread that my recent, very frequuent,
29-er punctures were probably pinch flats caused by too low tyre
pressure, I bought a track pump with built in guage.

A few puncture free rides at around 50 psi seemed to have resolved the
problem.

The only down point was a few days ago when I removed the tyre to do
some wheel truing. I decided to inflate it to 65 psi, the max on the
tyres range; just before getting to 65 there was a really loud bang as
the tube exploded!

New tube and back down to 50-55 psi.

Then today I got another puncture. Though I'd just bought yet another
spare 700x45c tube I decided to do a repair on the damaged one, partly
to save the hassle of having to take the wheel off.

It went OK, then I inflated the tube, no track pump available here so I
did my best with the hand pump, knowing that I wouldn't get it up to 50
psi.

I decided to get the tyre as hard as possible- as soon as I'd finished
there was a nasty sound of air escaping, and it deflated in seconds.

Annoyed now I took the tube out again to find another hole had appeared
in a different place! How could this happen without even riding the
thing?

As the hole was near the seam I decided to switch in the spare, and
managed to ride home on it without incident.

-------------

Can anyone offer useful insights into this problem, because I'm deeply
confused and on the verge of giving up 29-ing, if only because I've
bought four tubes (and a track pump) this month alone and can't justify
the expense.

My thoughts are that I do need to keep the pressure up with the track
pump to avoid pinch flats, but also that maybe I need to stay away from
the max of 65 psi.

So I'm currently going to stay at 40-45 psi and see what happens.

Would it be true to say that, given pressure is not so low that pinch
flats are a problem, that going much higher makes normal punctures more
likely?

Also, as the tyre ratings are meant for a bike, couldn't it be the case
that they would not apply when used on a unicycle, as, being one
wheeled, there will be around twice the stress on it?

Can anyone briefly explain what causes a pinch flat; I know the normal
explanation is that it's when the tube gets trapped between rim and
tyre, but, assuming that the tube is installed properly, how can this
occur. Certainly my flats seem to be happening on normal riding i.e. not
when dropping off curbs etc.

Has anyone else had problems with excessive 29 flats? One of my theories
is that maybe the tubes are faulty, possibly sat in the shop too long;
although this is no help as tubes don't come with a sell by date.

Another possibility is that, because my rim isn't designed for 29-ing
(it's the old style nimbus 700c and consequently quite narrow) that this
is causing the punctures. Although this wouldn't explain why it was OK
during my last big 29-er phase at the beginning of this year, when I was
riding every day for around a month and don't recall any flats.


--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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