We've owned a few TB's and I Learned that they cannot: turn quickly, start quickly or stop quickly. One time we were trail-riding, DH on our TB, DD on our (racing bred) QH, and me on my Arab ("Corporal".) We had been walking over one mile on this straightaway and decided it might be fun to race back. My Arab got ahead to start (my QH just kept up--he Never had a heart for racing), and my TB gained ground and past us, and he kept speeding up by "changing gears." This gelding could NEVER stop quickly. I always had to ask at least 3 strides from a gallop to transition back to a trot, even though my Arab could fly from a stop and performed a respectible slide stop, when necessary.