timing belt

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. Why it is called a timing belt is that it causes synchronize motion between a crankshaft and camshaft in automobiles. What that means is that the timing belt open and close the engine valves on time and that is why it is called a timing belt. Let us learn more about the timing belt, calculations, advantages, and disadvantages in this article.

Table Of Contents

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 a number of teeth similar to a gear.

In automobiles, the timing belt synchronizes the motion of the valve opening and closing based on the crankshaft position. In the case of a four-cylinder engine, the camshaft rotates at a half-speed than the crankshaft. What that means is 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
Source : Wikipedia

Like a traditional belt drive, the timing belt mechanism also has a driver pully and a driven pully. 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 pully, then the driven pully will rotate at a much higher speed than the driver pully.

Timing belt pulleys also have similar kind of teeth to engage with the belt. It is more or less similar to 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, with extreme heat in engines, it wears out easily. 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 so that it can 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 good 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, so it is about to get 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 less 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.

Frequently Asked Questions On Timing Belt (FAQ)

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