mismatch cascade

Next time there will be no mistakes.

I hadn't appreciated how much my chain was worn, nor how much a worn chain would chew the teeth off a new chainring. The chainring had to be replaced as the crank needed to be replaced and no-one wanted to sell a crank without chainrings to fit a square taper bottom bracket. If I'd checked the chain length back in September it might have been sufficiently worn to warrant replacement back then; as I'd not been putting too much torque through the worn crank whilst it had been needing to be replaced (to avoid the clicking screeching sounds it emitted as it rubbed against the BB axle) it's possible that a lot of the chain's lengthening had been relatively recent following replacement of the crank and resumption of maximal acceleration. As it was the chain was not replaced so in four months it ate enough of the middle chainring's teeth to make the chain slip when I set off. The extreme lengthening of the chain indicated inevitable severe wear to the sprockets, though this was taken on trust when I ordered a replacement cassette, somewhat harder to find than the replacement chain which had been sitting around for two weeks after delivery. The reason the cassette was so hard to find in stock was because I thought I needed a seven-speed block, probably due to last night being only the fourth night since May when I wasn't woken up at least twice. Using my partially-regained mental acuity I was able to spot a large gap between the smallest sprocket on the replacement cluster and the level at which the lockring would sit when fastened, though fortunately I noticed this in the safety of my own home rather than in TBW whither the rear wheel was taken today in order to get the old lockring removed after it defeated the borrowed lockring tool and home-made chainwhip yesterday. I've also only had the use of seven of the eight sprockets for some considerable time, partially the fault of the agèd gear cable which snapped the other week and partly down to the chain being so worn that it slid noticeably around the smallest cog as each tooth engaged, creating an unpleasant rumbling. Fortunately TBC had the V variant of the HG50 eight-speed in stock (as the existing one was the W it'll give me a slightly better lowest ratio) and were prepared to swap for the wrong one despite it having been de-packeted and lightly greased. The old one was temporarily replaced after an emergency clean (above) though I only had the new chain as the old one had been chopped up to make a chainwhip. There is an older chain somewhere upstairs which would probably have fitted the older sprockets better but I reasoned that I'd only have to deal with mismatched effective pitch for one day. After having to ride to work, to the shop, back to work and then home never applying any greater pressure to the pedals than might (approximately - I've no idea of the actual torque involved) crack the shells of two eggs placed beneath each foot to prevent the chain skipping madly (proving that the old cassette was substantially worn) it was extremely nice to get the correct-speed replacement emplaced early enough this evening to be able to pop out and test it later on. Combined with the clean-shifting cable it's almost like having a new bike.