These boots enable the wearer to run at the speed of a fast horse, viz. 24" base movement speed. 

For every 10 pounds (100 g.p. equivalent) of weight over 200 pounds, the wearer is slowed 1" in movement, so a 180 pound human with 60 pounds of gear would move at 20" base movement rate, and if a sack of 500 gold pieces were being carried in addition, the movement rate would be slowed yet another 5".

For every hour of continuous fast movement, the wearer must rest 1 hour. No more than 8 hours of continuous fast movement are possible before the wearer must rest.

Boots of speed give +2 to armor class value in combat situations where movement of this sort is possible.