( Yes, I have been here recently - just lurking though! )

A couple of weeks ago I had an unexplained puncture on the A361 in Devon; while negotiating the roundabout southbound at the junction with the A399 the front left suddenly deflated.

Fortunately there was a layby about ½ a mile ahead so I was able to reduce speed and pull off the road without any problems.

The AA man could not find any obvious cause when he examined the tyre while putting the spare on ( I do have a jack and brace, yes, but I doubt I have the muscle power to do the job properly myself and I had nearly 200 miles to go to get home... ). No cuts, no stones, no nails, no sidewall damage - none of the usual suspects, The valve was OK as well. The tyres were all in good condition with 5mm to 6mm of legal tread left.

Does anyone have any idea what could have caused this puncture?

Because it was unexplained and the tyres were only about 4,000 miles short of their lifespan ( I am told Pirelli 155/70s - which these wrre - last 20,000 miles; these had done 16,000 ) I took the precaution of having a whole new set on at the first opportunity, but I am still puzzled as to why it happened in the first place.

I am wondering if the tyres were simply "out of years" as I am a low mileage driver; I think they had been on the car for a bit over 4 years; that doesn't sound long enough to me for the UV deterioration to have really taken hold though?