The sublime joy of working on a bike
I'm going touring on my Thorn Raven (A Rohoff-equipped steel framed tourer) in two weeks so I started off my preparation today by washing it, for the first time, I might add! I've had it 10 months, but it has superb mudguards and doesn't get very dirty. That's my excuse anyway. I've never been a frequent washer of my bikes as often I'd be doing little else in this climate.
Having done that, I decided to try reversing the rear sprocket as I may have to do it on tour, and I'd never done it. I couldn't find the section in the manual so I started anyway, as one does. I've used numerous block removers in my time. I got my chainwhip, took off the quickrelease, put the sprocket remover on with it, got the chainwhip and started as one always did before, using the chainwhip clockwise. No budge. Got lever on it. No good. More effort. No budge. "Thinks...", as they say in comics. I wonder if it's the other way round?
I Dig and dig and find tiny reference in manual. I HATE manuals which don't have everything in the index. The manual says that the correct direction is the opposite of what I've been doing. Now it's going to be really tight! No! It comes off on the first effort. I clean it. Have taken chain off and cleaned it by shaking it in a bottle of diesel and then washing in water and detergent. Put chain back on, put sprocket on. Turn pedals. Chain climbs sprocket and comes off. Must be stiff link? No. Hmm. Maybe chain too tight?. Check that with experimentation on eccentric bottom bracket. No. I must have reversed the sprocket unknown to myself. Not sure when I look at pattern of wear. Check internet. Can find no pictures of worn Rohloff sprocket, or useful ones of other sprockets.
This is a picture of the sprocket, the wrong way round when looked at from right side of bike. This would be the correct way if I were fitting a new chain. You will see from this that there is a slight "hooking" of the teeth which in the wear pattern points towards the front of the bike, when it is the right way around. In other words the "hooks" will point towards the front of the bike as a sprocket wears. I've looked at this dozens of times in my time working on bikes, but it didn't really register until I needed to know it, and then what registered was that I was not sure!
It's sometimes amazing what's NOT on the internet. I constantly found this when I was practicing medicine. Decide to reverse its current position so see if I'm right. Works perfectly. If you reverse a Rohloff sprocket you must use a new chain as the teeth in that direction will be as new and won't mesh properly with a partly-worn chain. I oil the chain. Allow to dry outside. Put tools away. Go to get bike to put in the garage. The front tyre is punctured. There's a rusty tack stuck in it! It wasn't punctured 15 minutes earlier! I fix puncture and put a new tyre on as I was going to anyway.
Lessons learnt. Find out before doing anything even if it's really difficult to do so. Also, if I take anything off, photograph it first or mark it. Of course I won't fully obey my own advice. Who does?