One of my concerns when considering a 30 spd vs a 20 spd bike was the extra deralleur length required for a 30 speed chain and would this slow down shifting or make it less determinate. I was also interested in how useable all the gears were. I came up with the following table I'll share. My rules for useable gears were as follows. If I'm on the inside chainring then the outer two most gears on the freewheel would not be useable. Likewise on the outermost chainring the inner two most freewheel gears would not likely be used. On a thirty speed I adde a rule that on the middle chainring, the first freewheel gear would not be used and the outer most freewheel gear would not be used.
The unuseable gears are highlighted in yellow. The gears that are redundant are highlighted in blue.
What is interesting is that right in the mid range the useable gears jump by as large a factor as for the 20 speed bike with the finer gradations occuring near the top or the bottom of the range. Opposite of what I would want.
The cage has nothing to do with shifting. The cage is a chain tensioner. The shifting is done by the parallelogram, which is identical on the long and short cage. The long cage can simply take up more slack.The bottom of the chain is not under tension.
A triple is about having 3 speed ranges, NOT about having 30 gears.
The only unsusable gears with a properly set up triple are the big/big and small/small combinations, just like with a double.
The redundant gear combinations are there by design. This allows you to move between "speed ranges" (chainrings) without having to rack through 10 gears.
The choice between a double / triple should be dependant on your terrain. If you don't live in the mountains, not hills, mountains, you may not want to even consider a triple.
The only reason to get a triple is if you need lower gears. A triple setup will give you maybe 4 lower gear ratios than a double with the same cassette. If your choices are walking up a hill or buying a triple, then a triple is a good idea for you. Overlap is irrelevent.
That derailer difference is alot of nonsense and something the muppets regurgitate endlessly. I have both doubles and triples and can't tell the difference. Didn't seem to matter to Herras when he used a triple to win a vuelta stage either.
Originally Posted by antiquebiker
What he said.
Originally Posted by johnny99