Timing Belt: Calculations, Applications, Advantages And Disadvantages [PDF]

Like any other belt drive, a timing belt is used to transfer power from one shaft to another. It is called a timing belt because it causes synchronization motion between a crankshaft and camshaft in automobiles.

That means that the timing belt opens and closes the engine valves on time, which is why it is called a timing belt. Let us learn more about the timing belt, calculations, advantages, and disadvantages in this article.

What Is A Timing Belt?

A timing belt is a toothed belt responsible for transferring synchronized motion between one shaft to another. The outer side of the belt is flat, and the inner side of the belt has several teeth similar to a gear.

In automobiles, the timing belt synchronizes the valve opening and closing motion based on the crankshaft position. In the case of a four-cylinder engine, the camshaft rotates at a half-speed than the crankshaft. That means that for every two revolutions of crankshafts, there will be one revolution of the camshaft. This synchronization is only possible due to a timing belt.

timing belt

Like a traditional belt drive, the timing belt mechanism also has a driver pully and a driven pulley. Like gear drive, the ratio of teeth in driver pully and driven pully decides the velocity ratio. For example, if the driver pulley has more teeth than the driven pulley, then the driven pulley will rotate at a much higher speed than the driver pulley.

Timing belt pulleys also have similar kinds of teeth to engage with the belt. It is more or less similar to a gear drive, but the power can be transferred at a long distance.

In some automobiles, timing belt is also used to drive other parts like oil pump, water pump, injection pump etc.

A timing belt is usually made of rubber with high tension fibers. Since the timing belt is made of rubber, it wears out easily with extreme heat in engines. That is why some high-end timing belt is made of temperature resistant material like Highly Saturated Nitrile (HIS)

Timing Belt Length Calculation

Timing belt length for a simple two pulley drive can be calculated using the following formula.


What Is Timing Belt Tensioner?

A timing belt can perform its job when there is enough tension between the driving pulley and the driven pulley. When the timing belt wears out, it can not retain the same tension as before and occasionally skips to engage some teeth. This causes synchronization issues, especially in automobiles. That is why a Timing Belt Tensioner is used to keep the belt under proper tension to work properly.

timing belt tensioner
Timing Belt Tensioner

The timing belt tensioner is an integral part of the internal combustion engine to keep the timing belt under proper tension to keep it running.

Symptoms of a bad timing belt tensioner

Since the timing belt tensioner is an integral part of the engine, it is very difficult to diagnose if the timing belt tensioner went bad or not. We can diagnose the issue if we come across the following few symptoms.

  • Knocking sound from the engine
  • Engine misfires
  • The engine is not starting
  • Grinding noise
  • Check engine light
  • Irregular acceleration response

When you notice any of the above symptoms, you can assume that maybe your timing belt tensioner has gone bad. But at the same time, it could be the timing belt itself that might have worn out. To check that, you need a clear inspection by a professional technician.

Timing Belt Lifespan

Based on the types of material used in the timing belt, usually, it can last for about 60K-100K miles. But again it depends on how well you have maintained your car. Every car comes with its owner manual that says when you need to change your timing belt. But periodic inspection is always better.

Timing belt or timing chain: Which is better?

Since the timing belt is made of rubber, it is about to wear out after some years of usage. That is why nowadays many cars are coming with a timing chain. It is similar to a typical chain drive. The timing chain is more durable, and you don’t need to change it very often like a timing belt. But cars with timing chain is costlier than a car with a timing belt.

Advantages Of Timing Belt

Following are few of the advantages that timing belt has.

  • Very little noise compared to a timing chain
  • Less slippage issue
  • Constant velocity ration
  • Low maintenance
  • No vibrations
  • Cheap to replace a timing belt

Disadvantages Of Timing Belt

Here are few of the disadvantages that a timing belt comes with

  • Need to replace it very often
  • Need a timing belt tensioner to keep it under proper tension
  • Can transfer a relatively low amount of power

Application Of Timing Belt

Here are few of the areas where timig belt is used.

  • Automobiles
  • Sewing machines
  • Printers
  • Toys
  • Home appliances
  • Conveyor system


I hope you got a basic idea about the timing belt. This article is just a basic introduction, and when required, I will come up with more details about the timing belt and how to design it.

But for now, if you feel that you have some questions or queries, you can always ask that in the comment section, and I will be happy to help you.

You may also like to read: Types of engines

Frequently Asked Questions On Timing Belt (FAQ)

What is a timing belt?

The timing belt transfers synchronized motion between two shafts using two or more pulleys and a belt. The outside of the belt is plain, but the inside of the belt has teeth similar to gears.

How to tell if the timing belt has gone bad in a car?

If you notice any of the below symptoms, you may assume that your car timing belt might have gone bad.

Grinding noise
Knocking sound
The engine is not starting
Misfiring engine
The engine is not responding properly to the acceleration.


A 2004 batch Mechanical Engineering graduate From NIT, Agartala. Close to 16 years of experience in the field of consumer electronics and appliances domain as a Sr. Design Engineer and Team Leader in India and the United States. A GD&T practitioner, with expertise in Lean Manufacturing and Six Sigma. Crazy about exploring CAD-CAM tools and in his free time love to go for a ride with his champ, Rian.