Tyres

[Dead Eye]

Now the whole "which tyre, what pressure" thing has been done to death, so this is not what this thread is about, thank god.

I have a relatively fast leak on the rear tyre (a day ride out will easily see it drop from 40psi to below 10). I can't see any evidence of a puncture and I haven't time to fully investigate it further at the moment. But I don't recall hearing any hissing etc. It was suggested that maybe the valve was the issue.

Now the real question is, is it actually possible to replace the valve yourself?