Total tension required in a belt drive depends on the type of v belt, the design horsepower, and the drive rpm. Since running tensions cannot be measured, it is necessary to tension a drive statically.

The force/deflection method is most often used. Once a calculated force is applied to the center of a v belt span to obtain a known deflection, the recommended static tension is established. Most design catalogs provide force and deflection formulas.

With too little tension in a v belt drive, slippage can occur and lead to spin burns, cover wear, overheating of the v belt, and possibly overheating of bearings. Not enough tension in a synchronous belt causes premature tooth wear or possible ratcheting that will destroy the v belt and could break a shaft.

When installing a new v belt, installation tension should be set higher. Generally 1.4-1.5 times the normal static tension. This is necessary because drive tension drops rapidly during the seating-in process. This extra initial tension does not affect bearings because it decays rapidly.