Tire pressure question (1)

  Wondering about real life changes in tire pressure during the course of a race day.  If you put say 120psi in your tires at 5:30 am, what are the tires running later in the day with increased ambient temps and road friction from your (blazing fast) ride?

If memory serves correctly, from the math wizards posting before, per physics. Every 20 degrees in temperature equals 4 pounds of pressure.