Roman Heavy Cavalry Fighting Techniques

[Robert Vermaat]

It is a while since I have read it but he gives several descriptions of Macedonian cavalry entangled with their enemies in a sort of close order pushing match, certainly at the Granicus and at Gaugamela.

That would surely be interesting, because I'm told left and right that cavalry formations are not supposed to be able to do that, because one line of horses would not be able to 'push' the line of horses to their front without all kinds of chaos. Or is the sheer mass of the frontline of the cavalry already enough to generate enough weight against an infantry formation?