Originally Posted by
oldbobcat
Chain rub is a function of number of chain rings, width of rear cog cluster, shortness of chain stays, width of chain, and width of front derailleur cage. I just follow manufacturer specs. If you think you can do better, by all means experiment.
To me, that's the key. I don't know for sure, but I tend to believe that bicycles are all designed and components specified such that they do not have chain rub in any gear,
on paper. I find it hard to believe that a bicycle would make it into production if the design had chain rub built in. But the tolerances are so tight (especially on a triple) that when a human being installs and adjusts the derailleurs, even a small variance in derailleur height, rotation, or adjustment can cause rub. I can always achieve no rub, but they don't always come that way.
Once you start changing crankset, derailleur, rear cluster, or shifters, all bets are off.