Ibo speed is when they take an arrow 30 inches long, weighing 5 grains per inch, and shoot it out of a 30 inch bow pulling 70 pounds. This is the lightest possible weight it can shoot. And normally, the fastest speed the bow will produce. Now, the more arrow weight you have and the more stuff you have on your string, as well as if you let down your poundage, youre going to loose some of that speed. So, the speed your actually shooting depends on your setup.