They have a sizing chart to determine the amount of beads. I cheated and just added up the oz of wheel weights then rounded up to the next whole number. I ended up w/3oz in my 240 rear and 1 in my 120 front. When compared to their chart, I was correct in my assumption on the amount needed. Any rotating object will rotate around its center of mass. If you put a large weight on one side of the tire, the center of mass for the tire will move towards that weight,and the tire will try to rotate around that new center of mass. The result is that the ride will be rough as the tire is pounding the ground because the axle moves up and down, trying to keep the center of rotation ( which is now not the same as the center of the wheel) at a constant point. Now, if you put something inside the tire that is free to move, it will try to move to the point furthest from the center of rotation. That is because the force on the sand, golf ball, or equal is directly proportional to the radius of the rotation. This movement of the sand, or whatever will continue until the center of mass for the wheel is exactly at the center of the wheel (also known as the axle) At that point the tire is balanced until you stop and the stuff falls to the bottom of the tire. Whenever you start up, the whole balancing act resumes. If the stuff clumps, it can't move and the tire won't self balance.