Originally Posted by
DrIsotope
Not to mention unnecessary-- my chainline is perfectly straight when on the 6th cog, so there are 5 above and 5 below. It's only 35mm total between the center of the 1st and 11th cogs, so the chain is never deflecting more than 17.5mm, roughly 3/4". Unless carefully shifted, I imagine a triple would have greater amounts of possible deflection. Which is why I don't favor a triple-- above and beyond the duplicate ratios, there are gear combos you simply can't/shouldn't use.
A triple actually allows a straighter chainline, thanks to the "duplicate" gear ratios. Similar is the standard double. Compact doubles, without "duplicate" gears are worse on that account.