Originally Posted by
Tim_Iowa
Those compatibility charts are cool, but they don't address cross-capability between MTB and Road Shimano systems, which is the crux of this discussion.
They exist to on places like the Sheldon brown site, but take a little more searching but take a little more finesse. every generation of group set is basically the same just made from different materials, and to serve a different purpose either road or dirt. So it limits the cross compatibility across years and across purpose but of course with research anything is possible.