Originally Posted by
patentcad
A big enough difference that racing drivetrains switched over about 15+ years ago. My early race bikes (c. 1990) were 53/42, 53/39 is a more flexible combination. That 4 teeth reduction makes a meaningful difference in gear ratios when you get into gears like 39 x 23 or 39 x 25.
Actually the discusion is focused on the front, tripple vs. double, I suppose the gear combonation could have some effect on shifting but the original argument was the old standby that you cant shift a tripple. However your point is still valid from a gearing point of view. Dependant on what is on the rear