I bought a second hand bike with an existing Ultegra DI2 6770 groupset, which is a 10-speed group. I would like to upgrade the components required in order to have syncro shift on it.
As far as I know syncro shift is not available for 6770 (10-speed Shimano Ultegra Di2). For 6870 (the first 11-speed Ultegra Di2 version), Synchro shift is available if we update the battery to the BT-DN110. (Note: the battery houses the computer system that enables Synchro shift.)
Thus I am wondering what components I need to upgrade from a 6770 groupset?