Have a look at the teeth on the rear cassette on the gear you use most often. If they are a different shape from the others, it is time to change. If the chain is skipping under load, that is also a good indication. I seem to go through a chain and rear cassette every 5000 km or so. Bottom brackets should go, I think, for about 10,000 km.

In my case, I wanted to step up from the Acera kit I had, I wanted a better set of gear ratios. On my cruising gears I was having to change the front derailleur as well as the rear one. I had a look at the numbers and discovered that I could get two gears almost the same as the previous two, if I moved to a 9 speed setup.

This bike has to last me another 8 months, so this was a good time to upgrade, as I seem to go through a chain and rear cassette in about that time. After that I will hand the bike off to a friend, letting them know they should change the chain and rear cassette. I will keep the Brooks though I still have the original seat.

Will see if I can get the pic working! Surprised you cant see it if you are in China.

z