I decided to do some more fettling of my singlespeed bike in prepartion for Saturday's 200 km forum ride in Cheshire ...
I discovered that the sprocket is starting to look a bit worn. It wasn't even new when I put it on the bike and I have done 2,650 kms (1,650 miles) on it since then. Obviously, with only one sprocket rather than a full cassette worth, all the wear is going to be concentrated on that sprocket.
I found another used one with less wear in my spares box and was going to put that on but I couldn't get the locking ring off - I actually broke my chainwhip trying! I decided to postpone the job until after the Cheshire ride and the 100 mile York/Humber Bridge/York ride the following Saturday.
And then ... I noticed that the rear tyre had a worrying bulge in it. I wasn't going to risk riding on that tyre again so I took a photo of it and then put a replacement tyre on. (I'll finish off the dodgy tyre on my turbo trainer next winter.)
The tyre looked even worse in real life than it looks in this photo ...