Power transmission is a function of belt tension. However, as belt tension increases, so does the stress, or load, on the belt and bearings. The ideal belt has the lowest tension and does not slip in high loads. Belt tension is determined by measuring the force to deflect the belt a given distance per inch of pulley. Belt tensions need to be adjusted according to belt type, size, speed, and pulley diameters. Timing belts need only adequate tension to keep the belt in contact with the pulley.