Boxerworks.com

I was wondering...

I've had a couple of punctures recently. For me, this is really a rare anomaly. I ride a lot, on several different bikes/tyres, and generally I don't get punctures. In fact, up until last year, I can only remember having one puncture in more than 30 years of riding. Now in a just a couple of months I've had another two...

Which causes me to speculate on how the recent punctures occurred.

Some (pertinent?) background: I bought the 1979 R100RS in May 2012, so I'm unsure of the age of the tyres/tubes, but they were/are obviously old. The front, which punctured, is a Metzler ME33 Lazer. It has an older-style ME33 branding and is made in Germany. The current ME33s are made in Brazil and are branded differently. I'm unsure how long since the old style tyre was available but I suspect it's been at least five years, and possibly up to 10. Despite it's obvious age the tyre has performed without fault (on dry roads). It's now toast and will be replaced asap.

The first puncture (December): It happened when i was taking the bike to get a new rear tyre fitted (I know, the irony ). It was a warm day, I had ridden for about an hour. The tyre went totally flat while crawling in traffic on a freeway (and just about to enter a tunnel!). I managed to get off the freeway and through inner city traffic safely (phew!). On attempting to re-inflate the tyre would not hold air. On removing the tyre the tube was found to have a small hole. There was no obvious penetration mark or object in the tyre/tube. But i did find some small hard grains in the tyre. I didn't check them closely but (later) came to think that they could have worn through the tube causing it to deflate... they might have been grains of sand? The tube was replace with a new one.

The second (last week): The flat tyre was discovered when I'd stopped to refuel after a three hour ride. After parking the bike and having lunch I came back to it to find the front tyre flat. The ambient temp was quite hot. At the tyre shop a leak was identified. On checking, once again, no obvious penetration or object was found, but another small grain of 'hard stuff' was discovered (but once again not thoroughly inspected, d'oh!).

So, I was wondering: Can a small grain of sand lodged between a tyre and a tube rub through the inner tube and cause it to deflate? It sounds logical to me but what do ppl think? Has it happened to anyone? I thought it could have happened to an old (hardened) tube but the second puncture occurred with a tube only a couple of months old. Or was it just a coincidence

No matter: I'm definitely getting a new (clean) tyre and tube fitted before the next outing...

It's either a coincidence... or you will now have 60 years of puncture free riding... I'd be curious about the grainy stuff and how it got in there.

I would tend to think that after inflating the tube that any sand would be "trapped" and unable to move and rub on the tube. Just my 2 cents.

I've only ever had one puncture and that was one too many, it was an old bike that had been sitting for 10 years, I fired it up and took it for a 5 mile run... and got a flat. I replaced both tubes then .

As She'llbe be said, it's hard to see how a grain of sand could move around enough to hurt but it could give a repeated point impact and finally cause a failure .... if it was big enough.

A grain of sand wouldn't have to move anywhere as such, in order to wear away at one spot on a tube.
Each wheel revolution will make that grain wear the tube.
Am I dreaming when I think me33 were available 3 years ago?
Certainly well less than 10 years.

I reckon if a grain of sand was trapped between the tube and tyre the slight differential flex between the two could cause the grain to rub into/through the tube... but that's just what i reckon.

I'll ask Scott at Pablo's about the possible age of the tyre while I'm in there getting it replaced (soon). I'll also ask him about the "rubbing grain of sand" theory.

Got the new tyre (ME33)...
My tyre guy was unconvinced about the rubbing stone theory.
He reckons the old front (ME33) was "at least" eight years old.
AND he really doesn't like changing tyres on these rims... It took him the best part of an hour - and a burst tube - to seat the new tyre... earned his money that day.
He finally got it fitted after he burst the tube and removed the tyre from the rim and cleaned the rim with a wire brush... plenty of slippery stuff, air, and quite a few expletives were employed.
Tyre, including fitting: (still) $150!

Does your tire/tyre man also balance your wheel after fitting the tire? I found the shop I was using never moved or changed the weight on my wheel, so I started mounting and balancing my own. I might let them fit and I'll balance to save the expletives of pinched fingers and such.

$150 for a front tyre?? Thats cheap.
A new Bridgestone cost me $185 in Rockhampton
late last year. That was before fitting , environmental fees
for tyre disposal etc. Total about $220 .
As an owner of a Toyota Landcruiser Troopie
fitted with split rims, a grain of anything between
tyre and tube leads to deflation on the move
and the total wrecking of $250+ tyre and $30 dollar
tube and removal and fitting costs.
Did one this time last year, nothing in tyre
hole in tube.