On Jul 16, 8:38 am, Dan O wrote:
On Jul 16, 5:30 am, John B. Slocomb wrote:

"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

A good setup should allow shifting to any combination without
problems, but for riding along you ideally want a straight chain line,
so as you shift more toward one end or the other of the cassette for
more than some brief circumstances, consider finding a combination
that moves the chain laterally at the front and rear together, rather
than shifting way back and forth at one end. (too long sentence)

For me this amounts to two modes of operation: Outer chainring with a
few, closely spaced outer cogs for most riding, and middle chainring
with a few middle-to-inner cogs for gnarly steep climbing. (The inner
ring is for some as yet unimagined scenario, like hauling heavy loads
out from the bottom of the Grand Canyon. The inner cog is reserved as
bail-out gear and pie-plate.)

On my liesure (whjeelie) bike, the two modes are middle ring with a
couple of middle-ish cogs for riding around town, and outer ring with
a couple of outer cogs for top speed to the fire station.