Accessory belts or auxiliary drive belts have become increasingly relevant with the evolution of vehicles and their current possibilities. In fact, as FEAD (Front End Auxiliary Drive) systems have become less spacious in physical terms, their importance in terms of propulsion has also increased significantly, requiring more power capacity with fewer cylinders and space.

In such a context, the role of auxiliary belts has come to the fore, evolving considerably over the years in both design and materials. Some changes that were reflected in increasingly longer accessory belts and more durable materials.

In today’s article, we learn about the main types of transmission belts that are housed in the vehicle, and we talk about the particularities of each of them.

What is the main difference between an auxiliary drive belt and a timing belt?

Driving belts are power transmission devices that are able to transfer power between elements such as shafts, pulleys or sheaves. Although they may have a similar appearance, both play two completely different roles.

The timing belt is used to synchronize the rotation of the crankshaft and camshaft so that the engine valves open and close at the precise time for the intake and exhaust of each cylinder.

On the other hand, the accessory belt or aux drive belt is the one that transmits the movement of the crankshaft pulley to different components of the vehicle, such as the alternator to charge the battery and to power the electrical system when its engine is running or the power steering. It’s attached to the crankshaft and camshaft via several pulley, while the tensioner pulleys rest on the outside.

While the timing belt almost always has one side full of notches or teeth (they are called toothed or synchronized for that reason), the auxiliary drive belt usually does not have notches but parallel longitudinal grooves and is usually somewhat narrower and thinner than the first one.

Types of transmission belts and their application

Transmission belts are generally made of rubber and can be classified into different types depending on their application.

The auxiliary drive system transmits power from a drive pulley to accessories. There is the classic design with multiple belts that drive different accessories like the alternator and power steering pump. Although it is also common to find systems with a serpentine belt capable of driving all the accessories by itself. It is true that in some engines you can find toothed or synchronized belts such as timing belts driving an accessory, generally the two most common types of auxiliary drive belts are the following: 

V-belt

The V-belt, shaped like an isosceles trapezoid in cross section, is responsible for driving so-called secondary or auxiliary accessories. Years ago, this system activated elements such as the electric generator and the water pump, but now others have been added, such as the power steering pump or the Air Conditioning compressor.

These types of belts solved alignment and twisting problems by focusing on the pulley groove. And more importantly, they had a much stronger grip than the auxiliary belts of yesteryear because their shape is basically a wedge.

These belts are characterized by being thinner and smaller and generally only drive one peripheral at a time. So, it’s quite common to find multiple V-belts on an engine, but only one serpentine belt.

Currently, most of the modern applications of this type of auxiliary belt have been replaced by the ribbed or poly-V belt that we will see below.

Poly V-belt

The poly-V belt (also known as auxiliary ribbed belt, poly belt and poly vee belt) is a type of belt that has played a crucial role in the capabilities of vehicles to transfer greater power and overcome the challenges presented by today’s increasingly complex systems.

This type of belt is a further development of the V-belt and has several longitudinal grooves in its design.

As tension increases, this type of belt fits hard into the grooves, increasing friction and thus transmitting torques with minimal power loss.

Due to its flexibility and high efficiency, the Poly V belt has become one of the most popular choices among vehicle manufacturers.

For this reason, its multiple advantages take on more prominence than ever:

• Support higher loads.
• It’s more flexible.
• Allows enveloping angles in small spaces.
• Increased system performance.
• Support higher speeds.

Unlike other drive belts, it has its teeth or grooves parallel to the direction of the belt.

Choosing the right auxiliary drive kit will ensure the vehicle runs smoothly and efficiently over a longer life cycle.

When should an auxiliary drive belt be replaced?

An auxiliary drive belt has a very variable useful life depending on the use of the vehicle.

Made of highly durable synthetic rubber (Ethylene Propylene Diene type M or EPDM), it is a component that must be inspected visually to detect the need for its replacement.

If the belt is worn, it will have cracks, fraying or irregularities of all kinds.

Although among the most obvious symptoms of failure of the auxiliary belt system are:

• Steering hardening.
• Vehicle battery failure.
• Failure in the air conditioning.
• Humming in the engine.

Related content: Understanding the Drive Belt Tensioner (Friction Wheel)

Dolz Kits, knowledge and experience at your service.

The Dolz Kits Range includes:

• Timing Belt Kits with water pump.
• Timing Belt Kits without water pump.
• Auxiliary Drive Kits.
• Timing Chain Kits.

All of them are manufactured according to original equipment (OE) specifications and are guaranteed for 2 years from the date of purchase or 50,000 km.

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Practically 100% of internal combustion engines in any vehicle are equipped with a timing belt or timing chain system.

In today’s article we know the particularities of those systems, the main differences of the chain and the belt, and we also talk about the auxiliary drive system, increasingly complex and in demand.

Timing chain or timing belt drive

It is possible to differentiate distribution systems depending on several factors such as the position of the camshaft and the valves (SV, OHV or OHC), according to the valve actuation or the most well-known classification that is given by the distribution control, that is: distribution by belt or distribution by chain.

Among the main functions of the timing distribution are:

• Synchronize that engine timings are running at exact precision.
• Make the transmission valve work as it should. As speed is gained, all parts must speed up accordingly for the engine to exert potential.
• Starting up the vehicle’s engine.

Such is its importance within the engine gear that its malfunction can even affect the water pump or lead to a critical breakdown for the vehicle’s engine.

Timing Belt

The timing belt consists of an internal toothed part that allows the transmission of mechanical energy between a drive gear (the pinion) and another driven pinion. It is a silent transmission and requires rigorous maintenance due to being an element prone to wear.

Contrary to what happens with the chain, in this type of distribution there is no lubrication, so it is not necessary for it to be so hermetic. When the distribution is carried out by chain, this system is lubricated with oil.

Timing Chain

For its part, chain is made of links, like a bicycle chain, although more complex and robust. Among its great advantages is that it does not require regular maintenance. However, it makes more noise than the timing belt and is prone to slack, directly affecting engine performance.

Related content: All you need to know about Dolz kits

Auxiliary drive system

On the other hand, we also find the auxiliary belt transmission. An auxiliary drive system designed to transmit the power of the engine to the different auxiliary groups, some of them of vital importance such as the alternator, the power steering, or the water pump.

This need arises because current vehicles incorporate more and more electronic equipment to increase driving comfort, and these are activated through this system. Which has led to a considerable increase in the amount of torque to be transferred.

This function used to be performed by the V-ribbed belt but is no longer sufficient to drive the high output alternator and other front end accessories. 

Dolz, premium brand 

About us

With over 90-year history, Industrias Dolz is a European leader in manufacturing water pumps. In addition, we also supply timing chain kits, timing belt kits and thermostats in the spare parts industry for the aftermarket.

We have three factories in Spain (Castellón), Argentina (Buenos Aires) and China (Shouzou) and we have delegations in Argentina, Mexico, China, Poland, and Spain marketing our products in more than 70 countries around the world.

Range of Timing Distribution Kits

With a wide range made up of more than 250 references, Dolz Kits cover more than 90% of vehicle applications in the European market. 

Each kit contains everything necessary for a professional assembly and meet all OE quality standards.

Are you looking for a partner with experience in the aftermarket? Our combination of innovative technologies, industry 4.0 techniques and our in-house production, advocates for a multi-product structure, trusted renowned and qualified by the ISO quality standard.

Contact us for further information on our product range!

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