Blowout!

[fido]

The other day I went for a short run on the A7 just to go to the bank a get a few things in Asda. I was setting off to come back the pretty way via Rothes and experienced rapid deflation of the rear tyre. I managed to slither to a halt without the idiots behind running me down. A mobile phone call and 2 1/2 hour wait later a big towtruck came to take the bike home. I could not find anything stuck in the tyre and assumed the valve had torn out of the tube. I run low pressures, only a couple of psi higher than BSA specified because the bike is a rigid and softer tyres absorb some of the bumps. I didn't have time to investigate until today. It was not the valve but there is a hole in the tube. The tube seems to have worn thin at that point. There's nothing on the inside of the tyre to account for the damage so it looks like a case of internal abrasion between the  inside edge of the tyre and the tube. I suppose the low pressure may have caused this or perhaps it's just a dodgy tube. It is a Kenda tube, made in Taiwan.

[a10gf]

Sorry for what happened, it's a major annoyance indeed.

You surely know, but these puncture-fix spraycans can do wonders (within limits, of course, won't fix a ripped apart tube). After fixing a flat, I have continued riding for 1000's of miles after a puncture, with the stuff in there (waiting till the  tyre needs change due to wear), and see no special risk of sudden deflation or any other problem. The smaller cans for bikes or motorbikes have a nice size. I always bring one along, it has saved my day (or night) more than once.

[fido]

Is that the sort that inflates the tyre as it goes in? Does it pump them up enough to seat the tyre properly on the rim?

[a10gf]

Yes, as they fix tubeless tyres as well. Looking at the size of the can, the 'inflation power' is amazing.

[bsa- bill]

I had a puncture yesterday, managed to limp home on the flatish front tyre, it's an Avon AM20
Just checked the tyre it's ok , seems fine can't fined any evidence of being creased or chaffed, sidewall pretty firm all around.
Never thought about it before but it looks like an advantage of the Morad Alloy rim is the tyre stays on when flat, although I went very carefully on the mile home, HA a slow speed tank slapper - imagine.

Now to the point
The cause of the puncture was the small dished washer thing that fits on the tyre over the valve stem, this must have came off when the tyre was fitted, worked its way around the tube and eventually for some reason dug in.
I have had a look at a spare tube and the little washer on it is pretty well stuck to the tube although perhaps if I tried hard enough it might come off.
Now that my confidence in my tyre fitting skills has been called into question, my question is what is the order of the fittings on the valve stem and where do they go
This tube had on the valve stem starting from the tube - 1. the small dished washer, 2. a brass nut, 3. another brass nut.
I had them in the following order (tube) washer, rim, brass nut - the other brass nut I discarded

OK forum tyre Gurus what if anything have I done wrong (apart from letting the little washer fall off when fitting the tube)

[fido]

The one nut is supposed to go inside and butt up to the rim so the washer should always be kept in place by that inner nut. The other nut goes outside so in effect the 2 nuts clamp the valve holder to the rim.

[MG]

I always omit the nut on the outside, this way you can see when the tyre has slipped and turned on the rim, the valve will be skew to the rim then. By deflating the tyre you can easily turn it back into it's original position. This will admittedly happen very rarely, actually only with really good brakes and the tyre pressure set a bit too low maybe, but still.
If the valve is clamped with both nuts, it will always be held perpendicular to the rim, and if the tyre (and tube) turn on the rim continuously, you won't notice and it will eventually damage the tube.
Not my idea, it was an old racer who told me this, and I've done so ever since, works for me!

Cheers, Markus

[bsa- bill]

Thanks Fido and MG.

Seems I got that all wrong, Ok off to the corner with the pointy hat on

[chaterlea25]

Hi All,
Fido, you were LUCKY 
My advice is to only use "QUALITY" tubes
10 years ago I had a front tube burst due to a flake of chrome (as best I can figure out??)
Far eastern tubes will rip when punctured, this one did , a 4 inch split
I went arsre over kettle over the bars and did myself no good at all 

Now I'm paranoid and fit new tubes every time!!

HTH
John O R

[trevinoz]

I agree John,
                         I always make sure that the tubes I use are rubber.
There were some about which was made of butyl or some such rubbish and tore open with any puncture.

       Trev.

[bsa- bill]

The one I had in the front with the puncture is a Pirelli and behaved like a gent, I thought I would repair it but then I don't know how long rubber solution is viable for and mine is old old old, and the cost of a puncture repair at a tyre depot is much more then half the price of a good tube and more than the cost of a cheap tube.
My spare was bought as just that a spare get you home.
Going to Peebles bike show tomorrow so hope to pick up a good new tube there if not I'll mail order a couple.
Strange how your thinking goes off track at times, why did I buy a cheap tube as a get you home thing, if you have to put a tube in might as well put a good one once as put one in one your going to change when you get home, I suppose old habits from harder times stick