Originally Posted by
veganbikes
It was actually good advice, Shimano does a lot of compatibility charts to help us all out..
While Shimano puts great documentation out there, they tend not to mix generations in those charts, especially if you might be jumping 2 generations. There are often newer items that won't be listed in the older component compatibility and the new item compatibility won't show it compatible with an older generation component, even though they are fully compatible. Like I can use any 9 speed RD on a 6s index system which isn't going to show up in any compatibility chart