Originally Posted by
Steve_sr
Thanks for the clarification. I wasn't considering the 1X factor.
I think that the RX-810 comes with the 2X kit that will be going on the new bike. Wonder why Shimano doesn't mention the max cog size of 40-42 in the spec for the RX-810? Their "consumer" literature only mentions the 11-34/36 cassette with the 2X group.
From what I understand, the difference is in the path the derailleur takes. 812 takes a path more suitable to larger cogs. As many have experienced, it does work. Modern medium cage is yesterday’s looong cage.