Apparently every six out of ten Mongolian cavalry were light cavalries. Rest being either lancers or heavy cavalries. They avoided facing excessively armoured enemies like knights. They shot their horses to reduce knights' mobility then chased them down. Usually leaving a gap between their position so enemies can escape. Then chased them down to pick them off one by one.
Yes the military tactics of the Mongols is a great read. Note that their heavy cavalry was much lighter armored then the European equivalents. They also tended to have multiple horses for each trooper, increasing the speed they could move at by switching horses.
