Originally Posted by
ReluctantSamurai
Has nothing to do with the breed of horse.
While I am not a "Horse Whisperer", I did have the opportunity, when I was younger, to work with a horse trainer whose specialty was training teams of Belgians. Even match-paired from birth, there are big obstacles to overcome in getting a pair of horses to pull in perfect synchronization. One horse might be stronger than the other, one may respond to commands better or quicker than the other, and so on.
In a warfare situation you can add injury and battlefield stresses to the mix. Terrain will also play a factor, as even minor obstructions or hazards will slow a chariot. Net result is that you will likely never get a team to pull in perfect unison, whereas a single rider has only injury or battlefield stress to deal with.
IMHO, no team pulling a chariot could ever outrun a single rider.