Valve cap - tiny component, big problem !

I had new tyres fitted a couple of weeks ago. After a few days, the rear offside tyre had gone completely flat. I had a chat to a couple of people independently and they suggested I examine the inside of the valve-cap.

When I bought the car it was fitted with four of the Morgan-logo ones, I found the original box and there was a spare one, which I fitted. Evidently it wasn't seating properly due to a flattened and crumbly tiny O-ring (much worse than the one shown front-right in the photo), which was depressing the centre of the valve, and resulting in a slowish and inaudible leak. Something I've never encountered before.

I swapped them around, and the same happened when I put it on the front. I have since tried three other types, and the problem has not recurred. So I have fitted new caps all round, and all the tyres are now holding 24psi. Can't say as I've ever looked inside a valve cap before, but in future I will !

(I also ordered some replacement tiny O-rings online, as I like the logo'd caps -- anyone know who manufactured them ?).
[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]


Peter
2009 3-litre Roadster "Ivor", royal ivory / green