Originally Posted by
gsa103
1x11 is almost perfect for commuting. A 42-46t front and wide range rear give you the main range for commuting and eliminate the need for a front derailleur. The triple is dead, with wide range cassette you can cover the same gear range as a triple with a double or single and have greatly simplified shifting patterns.
You illustrated the problem with triples. A 50-39 shift requires no rear shifting. That means it's only equivalent to 1 gear change in the rear. If I only need to make a small change, why would I shift the front when I can shift the rear easier. The wider chainring separation limits cross-chaining, meaning you have to shift the front more often.
The other argument for triples is that "I mostly use the 39t gear", in which case a 1x11 solution is simpler, lighter, and eventually cheaper.
On a 1x11 drivetrain, the main concern with a larger chainring is the chainline. The chainring needs to be aligned roughly in the center of the cassette, ideally lining up with the 5th cog with an 11s drivetrain, so slightly biased toward the smaller cogs. If the chainring is too large, it may touch the chainstay when in the correct position. On my bike, with a 34T up front, there is about 2mm clearance between the chainstay and the chainring. Chainstay design obviously varies between frames, so this may be a larger or smaller issue, depending on your frame.