Originally Posted by
2 wheeler
I'm confused. The combination that you mention isn't extremely crossed over and yields the lowest gear ratio, which is sometimes very useful. So why do "knowledgeable cyclists" avoid this alignment?
He has it backwards. It should be large chain ring/largest cog or small chain ring/smallest cog. While this has been debated ad nauseam, the truth is it happens even with experienced riders. The system must accommodate all combinations, if only for a short time, without failing. The large front/largest rear and a shift to the small chain ring will sometimes cause the chain to drop, even when the FD is properly adjusted. This can happen when descending a hill using the large chain ring. Your start another climb and start dropping gears in the rear. You run out of gears in the back and drop to the small chain ring -- oops, dropped chain in the middle of a climb. The safer method is to drop one or two gears in the rear, drop to the small chain ring and drop or add gears in the rear as needed. I've see TdF riders drop chains like this. A chain catcher is a good way to prevent the problem -- professional riders use em, so do I.