"John B. Slocomb" wrote in message
...

"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.

As far as the chain and rear der are concerned all the cogs are in play from
the middle ring.

Not all setups will run without the chain rubbing the front der cage or big
chainwheel. If you can trim the front der all's good.