Originally Posted by
HendersonD
On my Transamerica ride I spent most of my time in the middle chain ring but certainly used the smallest chainring (granny gear) a lot. There were climbs where if I did not have the smallest chainring I would have needed to get off my bike and push it. For example, one climb in Idaho was an 8.7% grade for 3.5 miles. I will place a post in the touring forum
Herein lies the issue with doubles in some circumstances.
For the vast majority, a compact, subcompact, or even a 1x is the best option. But for others, I imagine more prevalent with tourers and an extra 50lbs, a middle ring that will go the width of a cassette might end up being the weapon of choice for a lot of miles.
It has little to do with running some chart to demonstrate the same available ratios with less duplicates. It has to do what the the ease of use, and convenience, that makes it almost function as a 1x in a lot of situation. At those times, there is little care if the same ratio could be found elsewhere in the gearing.
Back in the 52/42 days, most of my time was spent in the 42t in hilly terrain, or even where there were a lot of lights. The 52t was great on flats and downhills with open road.
John