Ian H said:
Pinch punctures are usually due to under-inflation. They manifest as two parallel slits close together. For narrow road tyres you need at least 70 - 80psi.
If it's a single hole then the cause is probably elsewhere. When you remove the tube mark where on the wheel/tyre the puncture occurs and carefully examine that area. Is it always the same place?
Exactly what I would have written, but you beat me to it.
Pinch punctures (or 'snakebites', so-called because of the characteristic parallel slits in the tube) should be a very rare thing and you should always know when you have caused one. I.e. you have just hit a pothole (or something else that you didn't manage to avoid) really hard.
The road surfaces round here are pretty bad, I'm pretty heavy (anything up to 16 stone) and I don't run my tyres at particularly high pressures (normally 80-95 psi) but it is very rare for me to get that kind of puncture; maybe once every 2 or 3 years. That is because I am careful what I ride over; if I can't go round a pothole or piece of debris, I bunnyhop over it. At the very least, I bend my elbows and lift myself out of the saddle to give the bike a chance to move underneath me if I'm about to hit something.
Whenever I do get a puncture (typically about 1 per 2,000 miles) I always perform a 'post-mortem' to find its cause, as described by Ian. Typically I'll discover a thorn or a shard of glass embedded in the tyre. If you leave those in, you'll just get repeat punctures in the future.
The other possibility is one that I suffered from early in my adult cycling career. I got snakebite punctures front and rear when I ran over a piece of 4" x 2" timber which had just fallen off a skip wagon in front of me. After that I got multiple punctures for weeks afterwards. They were driving me potty. In the end, I asked a more experienced cyclist for advice. He asked me how I was refitting the tyres after fixing the punctures. It turns out that I was damaging the tubes when I refitted them, causing weaknesses which led to further punctures.
I am now very careful when fitting tyres. I try to put them back on without using tyre levers. If I have to use levers, I am very careful not to damage the tubes with them. I am also careful not to trap the tubes between the rims and the tyres.
The extra care pays off. It is now very rare for me to get punctures, and when I do, I rarely repuncture afterwards.
IN total, it's been about 15.
