Originally Posted by
dstrong
I've sized chains both using big-big and small-small. My question is: How different is the final chain length using the two methods? It would be funny if with all this hand-wringing they yield the same result.
The answer is "it depends". Small-small on an 11-xx will always result in the same size. Big-big on an 11-23, 11-25, 11-28, and 11-30 will all result in different lengths. Which one if any will be the same as small-small? Who knows.
You can definitely say if big-big sizing results in a chain too long for small-small, and small-small sizing results in a chain to short for big-big, then you have the wrong rear derailleur for your drivetrain.
I use the small-small method so that I don't need to keep different chains for different cassettes.