Originally Posted by
oldbobcat
Half-step was popular in the '60s and some of us were still using it in the early '70s.
Related 1.5-step shifting is a pretty common consequence of many gearing schemes, sometimes even today. It's a useful thing to know how to do in lots of cases where you have a wide-range cassette and a ~10T gap between two chainrings.
and when going hard front derailleurs balked at dropping the chain to a ring that was only three or four teeth smaller.
What's the issue that comes up?
I haven't personally used a half-step system, but my general experience is that small gaps make for good shifting. When going up, the chain has less ramping to do, quicker to catch the teeth and get fully in the new ratio.
I haven't really thought about the big->small jump, as coercing the chain to drop down isn't generally very problematic. If anything, I'd think a small leap would help the chain get reliably caught, less likely to drop off the inside.