Originally Posted by Also, [i
why don't we see something like 4 front and 4 rear gears?[/i] It shouldn't be too hard to write up something that, when given min/max ratio, min/max gear size, and number of gears of front/back would assess all possible tooth counts to find the one with the most even spacing. I suppose it would make things a bit less intuitive - needing to change both the front and back gear for more of the jumps. Would be interesting to see that combined with computerized gear selection. That might be a project for another month though.
Don't forger that shifting the front is fundamentally different from shifting the back. Front is moving the tensioned part of the chain, rear the slack part. Before ramped and pegged cogs, we soft-pedaled for all shifts. Not necessary (but still nice) for rear shifts now; but front doesn't like to be shifted under power, and is more likely to drop the chain, or at least skip. This is (I believe) why 1x is becoming popular in mountain biking.
In the old half-step gearing mentioned above, both were shifted if you needed a small change in gearing. With down-tube shifters you could shift both with one hand. It is actually easier with todays indexed brake-shifters, but why bother with 9-11 (or is it 12) cogs on the back?