Originally Posted by
jdawginsc
Will the RX100 index with 8 speed brifters as long as the cassette is compatible?
Of course. The later RX100 groupset comes with 8 speed brifters. ie. the ST-A550.
As I mentioned earlier, you do need to swap out the FD-A550 in favor of a FD-A551 if you want to upgrade from the DT shifted RX100 groupset, to the brifter shifted RX100 groupset.