V-belt replacement guideline and how to read sizes by manufacturer

One of the parts necessary to operate vehicles and agricultural machinery is the V-belt. However, V-belts also deteriorate over time, so they must be replaced periodically. This article will explain about V-belts, including a guideline for when they should be replaced and how to read sizes by manufacturer.

What is a V-belt?

A V-belt is a type of fan belt. As the name suggests, it is a ring-shaped belt with a V-shaped cross section (trapezoid inverted). It transmits the power of the engine to machines that require rotational power, such as the power steering (steering wheel), air conditioner, water pump, and alternator, etc.

An engine cannot keep running by itself. Without a water pump to cool the engine, it would overheat, and without an alternator to generate electricity, the battery would run down. If the V-belt connected to the air conditioner compressor breaks, the air conditioner will stop working, and if the V-belt connected to the power steering pump breaks, the steering wheel will become abnormally heavy. It can be said that V-belts are essential for safe and comfortable driving of cars and agricultural vehicles.

Role of V-belts for each machine

  • Water pump...Circulates cooling water to prevent the engine from overheating.
  • Alternator...Charges the battery.
  • Cooling fan... Cools the radiator so that it does not overheat (not for electrically powered vehicles).
  • Air conditioner...Runs compressor for air conditioning
  • Steering wheel...turns pump for power steering

Some types of V-belts use a single belt to rotate all machines, while others use several belts to rotate each machine individually. There are flat belts as well as V-belts that use frictional force to transmit power, but V-belts have a larger contact area with the pulleys and a wedge-shaped cross section, so they bite into the V-grooves of the pulleys to prevent slippage, which results in stronger frictional force.

V-belt replacement guideline

Since the V-belt is made of rubber, it is a consumable item and will gradually deteriorate over time. If the rubber part cracks or loosens, each machine that the V-belt turns may stop working. If you continue to use it as it is, the belt may break, causing the car to stall or overheat, and the car may stop moving. Before this happens, make sure to perform regular maintenance and replace the V-belt. How often should it be replaced?

It is said that one guideline for V-belts is to replace them every 50,000 to 100,000 km. In addition, if you can visually confirm cracks, fraying, or bending, replace it immediately. If the V-belt becomes loose or deteriorated, it will make a strange ‘squealing’ sound when the engine is started or when accelerating. If you hear this noise, check the belt immediately and adjust or replace it.

Below is a list of points to consider when it is time to replace the V-belt. If any of these apply to you, we recommend that you have it inspected.

  • The vehicle has been driven more than 50,000 km.
  • The V-belt has cracks, fraying, or deflection.
  • Belt noise (squeal, whine, etc.) is heard from the engine compartment.
  • Air conditioner does not work anymore.
  • Water temperature rises.
  • The steering wheel suddenly became heavy.

Incidentally, if the V-belt has just been replaced but you still hear a squealing sound, the pulley may be rusted or otherwise damaged. It is a good idea to inspect the pulleys as well.

How to read sizes by manufacturer

There are many types of V-belts, and their dimensions are standardized in detail. Please note that the size notation method differs depending on the manufacturer.


Regular replacement of V-belts is important to prolong the life of your car. If left untreated, it can accelerate the deterioration of the car itself. Do not overlook signs such as belt squeal, and replace the belt at the appropriate time. When replacing the belt, be sure to check the size carefully.