Originally Posted by
DaveSSS
I have no giant hole in my gear shifting pattern, with a 48/32 and 11-34 12 speed. If you're doing any climbing that amounts to anything, you should always be in the little ring to start with, so you can progress from 17-19-22-25-29-34. If a 32/34 isn't low enough then a 46/30 or even a 44/28 crank might be needed.
A gear calculator says otherwise. Say you were in the 17 tooth gear at 90 RPM and a hill hoves into view. You down shift to the inner ring and all of a sudden you have to spin at 120RPM to maintain the speed or you coast until your speed hits about 10 mph slower or you shift gears on the back. The telling part is that the shift in the outer ring from the 17 tooth cog to the 19 tooth cog results in a change in speed of 2 mph while the change from the outer ring to the inner ring results in a 10mph change. Another way to look at it is that the transition from the wide range crank is the equivalent of 4 shifts on the back.
Now
compare that to a 50/40/30 triple. The speed difference between the outer ring and the middle ring is only about 6 mph. The shift won’t feel like you dropped a chain. Cadence has to increase a little but not that much. You don’t lose momentum at the bottom of a hill or have to change gears. The change between cogs while in the same ring is about 2mph as it is with the 48/32 but it’s a smaller transition between the rings. The number of shifts on the cog to get the same transition between the rings is only 2.
Originally Posted by
DaveSSS
When I do shift between the chain rings, I always make a 2 sprocket shift, immediately, so I'm in approximately in the same gear ratio as before the shift. With Campy, that takes one push of the finger lever or thumb button and about 1 second. My old 53/39/28 triple didn't work that much differently. A 1-cog shift isn't much easier or faster than a 2-cog shift.
Yes, and that’s the problem I see with the compact doubles. On a closer range double or triple, I can make a single shift to get about the same gear ratio. I don’t need to be fiddling with gears at the bottom of a climb and can concentrate on the climb.