SkipdiverJohn
Deplorable Brexiteer
- Location
- London
All engineering and the adjustment thereof, involves a degree of compromise. I have my gearing set up in the same way, so when I want a downchange it happens cleanly and quickly, so i get minimal loss of momentum. A slower change going up through the gears doesn't matter at all if riding on the flat. The compromise is getting good shifting without constant irritating clattering when not actually shifting.
Derailleurs are fundamentally crude drivetrains, no matter how many small refinements have been made to the tooth profiles.
Upchanges and downchanges are also fundamentally different. The tension spring on the rear mech means the gears always want to change up through the ratios to the smallest sprocket, and it's only the gear cable tension holding the selected ratio.
When you want to go down a gear and so into a larger rear sprocket, you have to slightly overshift the chain to force it to derail. If you don't slightly bias the indexing the right way, you can find yourself in the next index notch before the chain has moved. Then you have to make a half-change to the next gear to tip it over the edge then bring the lever back again. The cable tension ideally needs to be tight enough in each index notch that the chain will shift without having to move the lever almost two gear positions just to get a single ratio change.
10 and 11 speed stuff uses sprockets that are much closer physical spacing, and less movement of the mech is needed to derail the chain. The old-school stuff like five and six speeds that have wider spaced sprockets need more motion to achieve a change. Of course if you have friction shifters then there is no such thing as bad indexing, just bad rider operation!
