This time I haven’t got a question, but something that happened to me.
I suddenly found one morning that my tyre had gone soft. Not too much, so I pumped it up and went for a short ride. Next morning it had gone soft again so I reckoned I had a small puncture and took the tyre off and checked the tube out.
I could see no sign of a puncture so put some air in it before holding it a section at a time into a bowl of water. There was no sign of a puncture but there were a few bubbles coming up from the valve itself.
I’ve never had this before with the Presta type of valve so I was very surprised and thought I’d have to get a new tube. However I found that the valve unscrews and the central part or core could be removed and in fact replacements are freely available and cheap. It cost me about £5.00 for a pack of ten, but I may have been lucky. So I had to buy a pack of ten to replace just one, but I expect that I’ll need to use the others sooner or later, and I replaced the valve core put some air into the tube and checked under water again and there was no leak, so I refitted the tyre and everything was fine.
How could the valve suddenly start to leak after several years on the bike?
The valve is in effect totally enclosed inside an airtight rubber tube? What could possibly happen in there ? My guess is that every time we inflate our tyres we are pumping in air at the ambient temperature and humidity of the time and place. Chances are that this will be in the Summer because we do most of our cycling in the good weather, so when the weather changes, and Winter comes and goes year in and out, and any moisture in the air condenses out. The only metal inside the tube is the valve components, so it is possible that a little bit of corrosion can crop up.
The actual seal for the air is a tiny rubber disc and this, too can be affected by moisture and ever changing temperature. Mystery solved. I now know what to do if I get a strange leak that isn’t a puncture, just unscrew the valve core and put a new one in.
Sorted!