[Gaz64]

From Peterson Fluid Systems:

Tuesday Tech Tip:
Setting belt tension & HTD belts (radius tooth) vs. Gilmer belts (square tooth).
Unlike v-belts and serpentine style belts, toothed belts such as HTD and Gilmer's don't need to be overly tight. The teeth on the belt do the work, not the tension. The rule of thumb to check belt tension is you should be able to grab the belt in the center between the two pulleys and turn it 90 degrees so the teeth are facing you. If you can turn it 180 so the teeth are pointing straight up at you, its too loose. If you can't turn it 90 degrees, its too tight.
Over tightening belts can cause excessive belt walking and occasionally premature pulley wear.