Eaj,

You're correct on the old theory that the stallion influenced distance and the dam-side imparted the class, but in recent times, the Classic's have been won by colts who were sired by sprinters/milers but were out of dam's who female family had a lot of back stamina.

The ways of the world seem to be changing... it only makes sense though. Most of the commercial sire lines are very speed oriented and the stamina to get 10f+ will have to come from somewhere else.