Diagnosis: Puncture

(with apologies to Dick Van Dyke)

Punctures are frustrating.

But what can be even more frustrating is working out why they happen. And why they didn’t used to happen. And why they seem to be affecting perfectly good tyres and inner tubes…

IMG_1899
Giant S-RX4 tyres

My bike left the factory with these Giant S-RX4 tyres. They are a pretty high-volume hybrid tyre at 700x40c, and for well over 6 months and 1,000+ miles of city riding they did not cause me a single problem.

Then one day, I got a puncture. OK, these things happen, and it is pretty easy to repair.

Two weeks later, I got another puncture. I guess there must be a lot of debris on the streets at the moment.

The following week, another puncture. Starting to get a bit frustrating.

The next week  – two punctures – one of them on a family trail which could have easily spoiled the whole day (fortunately I had a spare inner tube after the previous repairs).

I really needed to work out what the problem was.

What I found strange was that the tyres did not have a huge mileage on them, and there was still plenty of visible tread. But then I noticed that small chunks of glass were getting embedded in the tread (and I mean really small – only a few millimetres across).

IMG_1897
You can just about see the tiny chunk of glass in the centre of the tread

It wasn’t taking much for these small chunks of glass to work their way through to the inside of the carcass, puncturing the inner tube.

But why was this happening now and not in the previous 1,000 miles?

Well, pliers and scissors helped to explain why…

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Cross section of the tyre

Put simply – the tyre is pretty thin and there doesn’t appear to be any form of puncture protection.

The rubber has worn down and is less than 3mm thick along the centre of the tread ( decreasing to 2mm at the edges). No wonder a 3mm chunk of glass can penetrate the carcass!

Goes to show that even a tyre with a visible tread pattern could be worn beyond its useful life.

Naturally, I decided that I had to buy some new tyres.

The two most popular puncture-protected brands seemed to be Continental and Schwalbe. You can normally count on German engineering. I chose the cheapest ones I could find and settled on the Continental Contact II.

While I was waiting for them to arrive, I got another FOUR punctures in just one week!

Fortunately, the Continental’s have yet to cause me a single problem. And I daresay that they feel a little faster!

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