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For various reasons, gravity mostly, I find cycling up hill a bit tricky.
So I decided to put some lower gears on my bicycle.
The buying process was complex enough
- it turns out that it is easy to get it wrong:
For various reasons, gravity mostly, I find cycling up hill a bit tricky.
So I decided to put some lower gears on my bicycle.
The buying process was complex enough
- it turns out that it is easy to get it wrong:
Shimano 7, 8, 9 and 10 speed gearing systems are only partly compatible.
Wider overall ratios beyond a certain limit mean a derailleur with a longer arm.
You can no longer buy a 12-28 8 speed block, and if you buy one with an 11 tooth sprocket, you might have to spend an hour with a grinder. - scroll to Hyperglide.
Those last two links were by the much-lamented Sheldon Brown who spent an awful lot of time putting information useful to cyclist up on the web.
At this point, to allay any suspense that might have been developing, I have to say here that the school-person error was not to test the existing system replacing a lot of it.
Anyway, I put on all the components and I oiled the cables - dry cables are the number one cause of poor shifting in my experience, do this first before any adjustment.
Would it shift cleanly all the way up and all the way down? - No.
There followed a few hours, spread over a couple of days, of frustrating put-it-back-as-you-found-it activity, which proved, one part at a time, that it was none of the new bits - the original system was also not shifting well either.
Finally, I narrowed it down to the short loop of Bowden cable outer that runs from the rear chain stay to the derailleur mechanism.
Although well-lubricated subsequently, water had been sitting in it since a very damp ride and had corroded the inside, forever preventing smooth operation.
Oh well. At least I had a reel of cable to hand.
Incidentally, Shimano gear cable outer is not spiral-wound like brake cable, but has a stiff cluster of longitudinal parallel wires held in place by a plastic sleeve.
This is a bit from another bike - the owner wondered why the gears were not working so well.
Although it cannot take anything like as much axial force as brake able, it compresses less for a given force making gear shifting, when all is well, is more accurate - it is one of the reasons the Japanese company could introduce 'indexed' shifting.
Those stiff wires are very hard, so always use cutters that are made for the job, I use one from Park, because not only are the jaws even harder, they are shaped so as not to crush the outer flat - a state from which it never really recovers properly.
By the way - I was going to write here that Mr Bowden both invented the cable and started the Raleigh bicycle company, but that nice Wikipedia says he probably didn't, but he knew a man who did.
'Alice'
Respond below, or to alice@electronicsweekly.com
