Drive belts need friction to operate. It sounds counterintuitive, but friction between the belt and the pulleys allows power transmission from the crankshaft to an alternator, power-steering pump or AC compressor. To produce these levels of friction, the belt and pulleys need surface area. This is why they have grooves that line up with great precision.
Just like a tire, the friction wears away at the belt, usually on the tops and walls of the ribs. Eventually, the grooves of the pulleys will bottom out on the grooves of the belt, and then the belt will not be able to generate friction and will begin to slip. If the narrow edge bottoms out in any of the belt grooves, the belt is worn and should be replaced.
Continental’s Multi-V Belt Kit provides a tool that measures the profile of the grooves on a belt. These eight teeth should fit in the grooves of the belt. If you can move the tool, the belt is worn below specifications. If the tool can’t move, you know the belt is within specifications. If you turn the tester and put your index and ring fingers through its holes, you can get into some tight areas. The edge should be set to the height of the belt groove. Technicians should press the narrow edge of the gauge into each belt groove, and the edge should not bottom out at any of the grooves.
Cracks in the belt are an indication of an issue, but with today’s modern materials, cracks are rare to nonexistent. The majority of the time the belts will be worn below specifications before cracking occurs.
This video is sponsored by Continental.
