Grinding media consists balls of 34 sizes (60mm30mm) in designed proportions with large sizes in feed end and small sizes in discharge end. About 27 to 35 % volume of mill is filled with grinding media. Equilibrium charge is that charge where compensation for wear can be done by balls of one size only usually the largest size in the compartment.
· Damage to the brake pads is caused by constant contact with the rotors and caliper. The backing plate may also come into contact with your brake pad, which also causes considerable damage over time. Grinding or squeaking noises are signs of wornout pads. It's one of the most common reasons for those sounds.