The new, mountain 12-speed barcon arrived for the Ridley cross bike conversion. The differences between it and the road shifter were obvious.
The light wasn't great, but the picture does show what I mean if you squint at it. The road shifter, silver, has a smaller cam and the stops defined by the shape of the shifter mount restrict its travel. The 12-speed shifter, black, has a larger cam and a wider angle between the stops. It handled the gear range easily.
Now that I know this, the barcon shifters I keep on hand for friction conversions will be 12-speed mountain just to assure that I have ample cable for whatever industry-defying drive trains I want to assemble. Once indexing becomes irrelevant, the possibilities proliferate.
This is less likely to happen with index-only shifting, because you have to push the shifter multiple times to move the derailleur. You could do it if you fired a bunch of clicks and then took your first pedal stroke, but not if you were continuously pedaling as you operated the shifter. With a progressive lever like the barcon, you can move the derailleur much more quickly than the chain can respond, increasing the chance that you could strand the chain out there. This problem is purely a product of the weird derailleur geometry and monstrous low-gear cogs used in currently fashionable wide-range gearing.
The rear derailleur exhibited a quirk I had already seen on other bikes. If you throw the lever to dump the chain across more than half of the cassette, the chain hops out on top of the arm to which the cable attaches.
Once the shifting issue was squared away, I could finish taping the bars and release this beast into the wild. There may be follow up tweaks, since it remains the most ambitious gear range I've attempted.
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