Originally Posted by
DaveSSS
12 speed cassette offerings are not likely to expand. The solution is a crankset with smaller chainrings. Then you can get the 1 tooth shifts in the same range as the current 17-18-19, but with the 15-16-17 instead. The 48/32 does just that. You won't see an 11-25 12 speed cassette.
The issue is the maximum percentage difference between adjacent cogs, not where it occurs unless that's next to the largest or smallest. With the big cog you do better not running out over having tighter spacing and coming up short. With the small cog you might prefer a jump over pedaling uncomfortably fast at a lower speed, although usually a good tuck is faster.
Most road riders don't like a 13.3% jump which is the 15-17 gap. In the 9 speed era the pro peloton ran 12-13-14-15-16-17-19-21-23 with just one gear bigger than the 13-24 cyclists like Eddy Merckx used in the mountains
A significant minority find 11.7% from 17-19 offensive. Some pros riding Campagnolo stuck with 12-23 moving to 10 cogs, although that was the point at which 11T became common outside time trial stages.
People seem OK with 10.5% from 19-21.
I put a few thousand miles on a 14-23 straight block to play with it. Adding the 20 cog was noticeable but not worth the hassle skipping over one more cog changing rings; and the 22 didn't make an appreciable difference.
Sure, small cogs running 17-19 work. However, my bike cost more than my car to get exactly what I wanted. Otherwise I might have continued riding my 1987 Univega.
Spinning 90-100 RPM a missing 18 tooth cog produces a gearing gap where neither cog is quite right at ~21 MPH with a 50 ring or ~16 MPH with a 40.
Different rings move it around but can't eliminate it.
50-40-30 x 13-14-15-16-17-18-19-21 8 cogs via the previous version of Mike Sherman's gear calculator.
That became 13-23 9 cogs in 2001 after Campagnolo eliminated 13-21 8 speed, then 13-26 10 in 2012 after a discontinued shifter spring broke.
