A Complete Guide to Timing Belts

Is a timing belt the same as a cam belt? In one word, yes!

The terms cambelt and timing belt refer to the same component. The use of these terms may vary depending on the region or manufacturer, but they both refer to the same type of belt. So, if you're unsure whether you need a cambelt or timing belt, the short answer is they are the same thing!

Despite their similar names, timing belts and timing chains are not the same components. Note that a timing chain is a physical linked chain, like a bicycle chain. This is opposed to the rubber loop typically found in a standard cambelt setup. Each configuration has upsides and downsides.

The main benefit of a timing chain is that its metal construction makes it much more hardwearing, and far less prone to periodic replacement. Timing chains need constant lubrication to function properly, are louder in operation than rubber or fabric-type belts and can cause far more severe and widespread damage on the rare occasions that they fail catastrophically.

Moreover, timing chain tensioners are controlled by engine oil pressure. This means it becomes even more critical to maintain this at the correct bar level at all times. By contrast, water pump pressure dictates the proper functioning of cambelt tensioners, which is why you’ll often get a recommendation to replace your water pump at the same time as having a new timing belt fitted.

Drive belts and timing belts are both key components, but they serve different purposes and have distinct characteristics. Here are the similarities and differences between drive belts and timing belts:

Similarities:

1. Both drive belts and timing belts are types of belts used to transfer power from one rotating component to another within the system
2. Both belts require proper tensioning to ensure effective power transmission and prevent slippage

Differences:

1. Drive belt and timing belt function is the primary difference between the two. A drive belt transfers rotational power, whereas a timing belt synchronises rotation to ensure timing is correct
2. Drive belts are exposed to wear and tear due to constant use. They require periodic inspection for damage and should be replaced to avoid component failure. Timing belts have a critical role, and their failure can cause significant damage, so preventative maintenance is recommended. Most manufacturers advise replacing timing belts at specific mileage or time intervals
3. Drive belts typically employ automatic tensioners, which maintain the proper tension in the belt, ensuring optimal power transmission. Timing belts, on the other hand, often use manual tensioners or a combination of manual and automatic tensioners
4. Drive belts are usually wider and thicker than timing belts. Timing belts have teeth or cogs on their inner surface. These teeth engage with corresponding teeth to provide precise timing

We know that a cambelt is a vital component of internal combustion engines. However, what does a timing belt do, exactly, and how do different types of timing belts play similarly crucial roles in a variety of other systems and mechanisms?

Timing belts are typically ridged with a circumference of protruding rubber teeth, and in an engine, it’s these teeth that enable the loop of timing belt material to turn the camshafts via the crankshaft as the various parts rotate at a consistent ratio of speed. Together, these components are thus responsible for opening and closing the intake and exhaust valves in an engine.

When a cambelt is in good working order and functioning correctly, the opening and closing of these valves are maintained at an optimal rhythm to match the up-and-down motion of pistons within the engine’s cylinders, allowing for the smooth and efficient functioning of the entire apparatus as the engine cycles through each of its various strokes (usually intake, compression, power, and exhaust).

In the case of a broken or failing timing belt, engine valves can be left stuck in an open position. This risks serious damage to the mechanism of so-called interference engines if they can be struck repeatedly by the pistons. Non-interference engines avoid this particular complication by keeping the valves and pistons separately confined. However, the engine will still be immobilised without a functioning cambelt installed.

As timing belts loop around a series of pulleys to connect up all the relevant engine components in sequence, they tend to rely on a number of tensioners to keep the ideal tension on the belt along its full length. These will usually need to be replaced along with new cambelts, as they’re almost always roughly the same age as the main belt and have a similar expected lifespan.

Due to the particular role timing belts play in synchronising the rotation speed of two differently sized shafts, there are many variables to be taken into consideration when assessing the correct belt size for the application and system you need it to fit.

Key factors to consider include cambelt width, material, and the number of teeth or pitch. Common timing belt pitch ratings include 3mm, 5mm and 8mm, but the correct choice will depend entirely on the specifics of your system or project, as well as overall power transmission requirements and the various shaft speeds in the mechanism it’s being fitted to.

Both the environment in which the timing belt is being fitted to work in and the subsequent suitability of material choices will also have a profound impact on the precise sizing and configuration of the best timing belt for your needs.

Timing belts are significant components in many mechanical and industrial systems. Three of the more common applications are as follows:

Timing belts on conveying systems are usually toothed or ridged. When used in combination with a toothed conveyor pulley, they allow for precise and responsive belt movement control and traction. For an array of industries including packaging, automotive manufacturing, distribution, and many more, this ability to accurately manoeuvre and position products and parts is key to the smooth running of the overall operation.

All timing belts are essentially power transmission belts, insofar as they transfer power through the rotary motion of one or more components from one part of a machine to another. Specialist power transmission belts can be manufactured to very high-performance levels for installation in a wide range of challenging applications. These include always-on industrial processing and heavy-duty agricultural machinery.

Linear positioning belts are used in applications where high accuracy is required to manoeuvre and position components or parts. Polyurethane timing belts are often favoured in this sort of environment because they tend to have relatively little stretch compared to more standard neoprene-type cambelts. This means there’s less chance of slippage or tooth deflection. This is significant in linear positioning and conveying roles, where the belts are subject to very different load patterns than rotary motion and power transmission timing belts.

• Trapezoidal belt - this type of tooth arrangement features flat-topped square ridges. It’s perhaps the most frequently seen timing belt type in many applications. It is usually the leading choice for linear positioning belts and other precision conveying roles. Trapezoidal teeth are highly effective for force transmission. However, at higher torques or speeds, they can show a tendency towards faster wear due to an increased concentration of stress forces on teeth of this shape
• Curvilinear belt - these feature a smoother and more rounded tooth shape, usually with deeper ridges between teeth than trapezoidal belts. The latter characteristic reduces the risk of tension loss (belt ratcheting), while the slightly refined shape of curvilinear teeth helps to alleviate the higher concentration of stress forces suffered by trapezoidal teeth under increased speed and torque demands. The downside of curvilinear belt profiles is a slightly increased degree of backlash - the amount of play between belt teeth and pulley grooves - which usually results in less accurate positioning
• Modified curvilinear belt - this is a further refinement of the above belt type that attempts to deliver a compromise between the strengths of both curvilinear and trapezoidal tooth profiles. A shallower tooth depth is offset by steeper-sided teeth (flank angles), meaning it can transmit force effectively at considerably higher speed and torque than the other two profile types while also avoiding ratcheting risk to an increased extent. This makes modified curvilinear belts a leading choice in many highly demanding industrial applications

Timing belts of all types play a vital role in the smooth running of engines and other power transmission systems. While they’re an extremely common and widely available component seen in myriad day-to-day environments and applications, selecting the correct type, material, size, and tooth profile to cope with the demands of its intended role is just as important as sourcing from a reliable brand and supplier.

For further information on cambelts, diagnostics, tension gauges, alignment tools, and all other aspects of power transmission systems and accessories, our support team will be happy to help.