Complete Guide: Timing belt

Jun 15, 2023

Timing belts play an improtant role in various mechanical systems by ensuring precise and synchronized movement between the engine's crankshaft and camshaft. As a key component in many vehicles and industrial applications, understanding the basics of timing belts is essential. In this article, we will delve into the world of timing belts, exploring their composition, types, materials, features, applications, installation and maintenance procedures, as well as comparing them to timing chains. Whether you're a car enthusiast or an engineer, this comprehensive guide will provide valuable insights into the world of timing belts.


What is a timing belt?


A timing belt is a belt-like transmission device made of materials such as polyurethane (PU), used to transmit power and achieve synchronized movement between shafts. Compared to regular belt drives, timing belts offer higher transmission efficiency and more precise motion control capabilities.

Polyurethane (PU), being one of the materials used for timing belts, possesses excellent wear resistance and resistance to hydrolysis, allowing the timing belt to be used for extended periods in harsh working environments without easily getting damaged. Additionally, polyurethane material exhibits good flexibility, enabling the welding of various shapes of blocks on the back of the timing belt to form a multi-functional conveying timing belt.

The presence of these blocks allows the timing belt to achieve diversified functions. For example, by installing a timing belt with protruding blocks, it can be used for conveying and transferring objects. The shape and spacing of the blocks can be designed and customized according to specific requirements to adapt to different application needs.

In summary, polyurethane timing belts, with their characteristics of wear resistance, resistance to hydrolysis, and flexibility, serve as reliable transmission devices. By welding different shapes of blocks on the back, they enable diversified conveying functions, providing efficient and precise motion transmission solutions for various industrial sectors.



Timing belt composition


A timing belt consists of several components, including the tension member, cover layer, and blocks. Here are the functions and requirements of each component:

Tension member: The tension member is typically made of high-strength materials such as steel wire or Kevlar. Its main function is to bear the primary tensile force of the belt drive. The tension member needs to possess requirements such as high tensile stiffness, long fatigue life, and constant length to ensure that the timing belt can withstand high tension and maintain stable performance during the transmission process.

Cover layer: The cover layer is the part that covers the tension member and is usually made of materials like polyurethane. Its main function is to transmit shear forces while ensuring lateral stability during the motion of the timing belt. The cover layer needs to have characteristics such as high strength, strong resistance to abrasion, and good oil resistance to ensure that the timing belt can maintain stable transmission performance under high loads and harsh working environments.

Blocks: Blocks are welded onto the back of the timing belt and can be customized in shape and size based on specific functions and requirements. The purpose of the blocks is to provide blocking or fixing capabilities for fixtures or workpieces. Depending on the application needs, the blocks can have different shapes and sizes to adapt to various working scenarios.

By properly combining and designing these components, a conveying timing belt can provide reliable transmission performance and diversified functionality. The tension member bears the primary tensile force, the cover layer transmits shear forces and provides lateral stability, while the blocks offer specific functionalities and the ability to fix fixtures. The collaborative work of these components makes the conveying timing belt an important transmission device widely used in various industrial sectors.

timing belt composition timing belt composition

Timing belt types


Rubber Timing Belts: Rubber timing belts are made of a rubber material with teeth on the inner surface. They are widely used in automotive engines and other industrial applications due to their flexibility, durability, and cost-effectiveness.

Polyurethane Timing Belts: Polyurethane timing belts are known for their high strength, abrasion resistance, and chemical stability. They are often used in applications that require precise positioning and synchronization, such as robotics, CNC machines, and printing presses.

Steel Cord Timing Belts: Steel cord timing belts have a steel cord reinforcement layer embedded within the belt material. This reinforcement provides high tensile strength and allows for greater load-carrying capacity. Steel cord timing belts are commonly used in heavy-duty applications that require high power transmission.

Double-Sided Timing Belts: Double-sided timing belts have teeth on both sides, allowing for power transmission from both sides of the belt. They are often used in applications where reversing or bidirectional power transmission is required.

Specialty Timing Belts: There are also specialized timing belts designed for specific applications. For example, high-temperature timing belts are made of heat-resistant materials for use in environments with elevated temperatures. High-torque timing belts are designed to transmit higher torque loads, while silent timing belts are engineered for reduced noise and vibration.

The choice of timing belt type depends on factors such as the application requirements, load capacity, speed, environmental conditions, and specific industry standards. Selecting the appropriate timing belt type is crucial to ensure reliable and efficient power transmission in a given application.


Materials of timing belts

Timing belts are made from various materials, depending on the specific application and requirements. The most common materials used in the manufacturing of timing belts include:

Rubber: The main component of timing belts is typically a specially formulated rubber compound. Rubber provides flexibility, durability, and resistance to wear. It also helps in absorbing vibrations and noise.

Reinforcement Cord: To enhance the strength and stability of the timing belt, reinforcement cords are embedded within the rubber. The cords are usually made of high-strength materials such as fiberglass, aramid (Kevlar), or carbon fiber. These cords provide the tensile strength necessary to withstand the loads and stresses during operation.

Fabric: Timing belts often have a fabric layer on the tooth side, which helps in reducing friction, noise, and wear. The fabric can be made from materials like nylon or polyester.

Tooth Coating: Some timing belts have a tooth coating or facing to improve their grip and performance. The coating can be made of materials like nylon, polyurethane, or rubber, which offer enhanced friction properties and wear resistance.

Metal Inserts: In certain cases, timing belts may have metal inserts or reinforcements embedded within the rubber to provide added strength and stability. These inserts can be made of materials like steel or aramid.

It's important to note that the specific composition and materials used in timing belts can vary depending on the manufacturer, the intended application, and the desired performance characteristics. Different industries and applications may require specific materials or variations in the construction of timing belts to meet their unique requirements.

Features of timing belt


Accurate Power Transmission: Timing belts ensure precise power transmission with no slippage, maintaining a constant transmission ratio. The teeth on the belt engage with the corresponding teeth on the pulley, ensuring accurate and reliable power transfer.

Smooth and Low-Noise Operation: Timing belts operate smoothly, resulting in minimal vibrations and low noise levels. The flexibility and damping properties of the rubber material help reduce noise and ensure a quiet operation.

High Transmission Efficiency: Timing belts offer high transmission efficiency, with values reaching up to 0.98. This high efficiency translates to reduced energy losses, making the system more energy-efficient and cost-effective.

Convenient Maintenance: Timing belts are easy to maintain and require no lubrication. This feature eliminates the need for frequent maintenance and reduces maintenance costs. Additionally, the belts are resistant to corrosion, further minimizing maintenance requirements.

Suitable for Long-Distance Transmission: Timing belts can be used for long-distance power transmission, with center distances exceeding 10 meters. This makes them suitable for applications that require power transmission over extended distances.

Conveying and Positioning Function: In addition to their primary power transmission role, timing belts with a specific design can also function as conveyors and provide precise positioning capabilities. This makes them versatile for applications requiring both power transmission and material handling.

Overall, timing belts offer accurate and efficient power transmission, smooth operation, low noise levels, and easy maintenance. They are suitable for various applications across industries, providing reliable and cost-effective performance.


How to select a timing belt

Selecting the appropriate timing belt involves considering the following steps:


Determine the transmission parameters: Based on the power requirements, speed demands, and other parameters of the application, choose the appropriate tooth profile type. Tooth profile and belt width can be selected based on load conditions, experience, or more detailed calculations considering power transmission and speed.

Consider correction factors: Determine load correction factors, speed ratio correction factors, pulley deflection correction factors, etc., based on factors such as equipment operating time, transmission ratio, and tensioning method. Then, calculate the width of the timing belt based on these correction factors, design power, and transmission capacity, and make corrections for power and transmission ratio.

Calculate the timing belt length: Calculate the length of the timing belt based on the matching timing pulleys and their installation positions. This helps ensure the correct transmission ratio and accurate synchronization.

Consider flanges and spacing: Select appropriate flanges and determine their spacing based on the function of the transmission and the shape and fixing method of the transmitted product (such as fixtures). This provides additional positioning and blocking functions to ensure the stability of the transmission process.

Verify manufacturing processes and capabilities: Check the manufacturing processes and capabilities of the timing belt based on the calculated tooth profile, width, length, as well as the shape, dimensions, and spacing of the flanges. For example, polyurethane jointed belts require a circumference greater than 600mm for processing, and the thickness of the flanges should be less than 1.2 times the pitch.

Record the timing belt model: Write down the corresponding timing belt model based on the selected tooth profile, width, and other parameters for ordering and use.

These steps can help you select the appropriate timing belt and ensure its reliable performance and transmission in your application. It is important to consult the manufacturer's technical specifications and usage guidelines for the best selection and installation practices when choosing a timing belt.


select timing belt


How to install, remove, and maintain a timing belt



Cut off the power supply to the machinery to ensure safe operation.
Confirm if the timing pulleys are in the same plane. If not, make adjustments to align the mating timing pulleys as closely as possible.
Loosen the bolts and reduce the shaft distance to allow easy installation of the timing belt onto the timing pulleys.
Tension the timing belt by aligning the belt teeth with the tooth grooves of the pulleys, gradually adjust the center distance, and tension the timing belt.
Tension the timing belt to the specified tension. You can use a timing belt tension gauge for measurement or adjust based on experience.
Check the alignment of the timing pulleys using a straightedge. If any abnormalities are found, remove the timing belt and readjust.
Securely fasten the installation screws on the tension side of the timing pulleys to ensure they do not move.
Check the meshing of the timing belt and timing pulleys to ensure proper engagement.


Cut off the power supply to the machinery to ensure safe operation.
Loosen the installation screws on the tension side of the timing belt to release the tension.
Gradually reduce the shaft distance to loosen the timing belt and easily remove it.
Remove the timing belt from the timing pulleys, taking care not to damage the belt teeth and grooves.
Check the condition of the timing belt for wear. If any damage or severe wear is found, replace it promptly.


install timing belt


When performing routine maintenance, pay attention to the following items:

Check if the installation tension of the timing belt has significantly decreased. Normally, the installation tension may slightly decrease after running for some time, but as long as the correct tension was applied during installation, re-tensioning is not necessary.
Inspect the back of the timing belt for cracks and whether the flanges are loose or detached.
Check the tooth root of the timing belt for cracks.
Flip the timing belt and check if the rubber layer or core wire is exposed due to wear at the tooth spaces and tooth bottoms.
Inspect the side of the timing belt for wear or damage caused by friction with the timing pulley flanges.
Check for significant lateral oscillation of the timing belt during operation.
Is there any water or oil residue on the timing belt?
Are the baseplates loose?
Are the tooth surfaces or flanges of the pulleys rusted?
Is there more noise than usual?

Timing belt VS Timing chain


Construction and Material:

Timing Belts: Made of a flexible, toothed belt typically constructed from rubber or synthetic materials.
Timing Chains: Made of metal links that interlock with toothed sprockets on the crankshaft and camshaft.
Durability and Lifespan:

Timing Belts: Generally have a limited lifespan and require regular replacement as part of preventive maintenance. They typically last around 60,000 to 100,000 miles (depending on the manufacturer's recommendations) before needing replacement.
Timing Chains: Generally more durable and have a longer lifespan. With proper maintenance and lubrication, timing chains can last the lifetime of the engine.

Timing Belts: Require regular replacement as part of maintenance. Replacement intervals vary depending on the manufacturer's recommendations.
Timing Chains: Generally require less maintenance. Maintenance is typically limited to inspection for wear and proper tension, and occasional lubrication.
Noise and Vibration:

Timing Belts: Generally quieter and smoother in operation, resulting in less noise and vibration.
Timing Chains: Can create more noise and vibration, especially as they age and wear.

Timing Belts: Typically less expensive than timing chains, including the cost of replacement.
Timing Chains: Generally more expensive than timing belts due to their construction and materials.
Performance and Application:

Timing Belts: Commonly used in passenger cars, light-duty trucks, and some motorcycles. They are suitable for most everyday driving conditions.
Timing Chains: Often found in larger vehicles, such as trucks, SUVs, and high-performance cars. Timing chains are preferred in applications where durability and resistance to extreme conditions are crucial.

Timing Belts: While reliable under normal operating conditions, they may be more prone to damage or failure in extreme conditions, such as high temperatures or contaminated environments.
Timing Chains: Known for their durability and reliability, especially in demanding conditions and high-performance applications.
Ultimately, the choice between a timing belt and timing chain depends on factors such as the specific engine design, manufacturer's recommendations, vehicle application, and personal preferences. It's important to follow the manufacturer's guidelines for maintenance and replacement to ensure proper engine performance and longevity.

FAQs About Timing Belt


Q: What are the reasons for early breakage of synchronous belts?
A: Possible reasons include inadequate consideration of the inertia forces of the driven pulley and passive load, excessive load or accidents causing the driven pulley to stop rotating, or using undersized pulleys leading to belt bending. Solutions include improving the design, replacing appropriate pulleys, and exercising caution during operation.

Q: How to address edge wear issues of synchronous belts?
A: Possible causes include incorrect parallelism of pulleys, insufficient bearing rigidity, or deformation of the belt pulley flanges. Solutions include correcting the pulley positions, increasing bearing rigidity, correcting the flanges, or replacing the pulleys.

Q: Why do the tooth surfaces of synchronous belts wear out?
A: Reasons may include excessive load, excessive tension, inclusion of abrasive particles or rough tooth surfaces. Solutions include improving the design, adjusting the tension, improving the environment, or refining the tooth surfaces.

Q: What are the causes of tooth breakage in synchronous belts?
A: Possible causes include tooth jumping or increased load due to mechanical accidents. Solutions include checking the design, adjusting the appropriate tension, increasing the pulley diameter, or eliminating passive mechanical failures.

Q: How to address the issues of backside wear and cracking in synchronous belts?
A: Possible causes include restricted rotation of the tensioning pulley, misalignment of the tensioning pulley, contact of the belt with mechanical frameworks, or prolonged exposure to low temperatures. Solutions include repairing or replacing the tensioning pulley bearings, correcting the position of the tensioning pulley, inspecting and correcting the mechanical components, or improving the ambient temperature.

Q: How to resolve longitudinal cracking issues in synchronous belts?
A: Possible causes include the synchronous belt running beyond the edge of the pulley or the belt riding up on the flanges of the pulley. Solutions include adjusting the pulley position and increasing bearing rigidity while ensuring secure fixation.

Q: How to prevent partial fracture of the tension members in synchronous belts?
A: Proper installation and removal of synchronous belts should be ensured, avoiding the inclusion of impurities or sharp residue. Improving the environment and implementing protective measures are also recommended.

Q: How to reduce the operational noise of synchronous belts?
A: Adjusting the tension of the synchronous belt, ensuring parallelism of the two shafts, avoiding the synchronous belt width exceeding the pulley diameter, reducing the load, and inspecting the meshing condition between the synchronous belt and pulleys can help reduce noise.

Q: How to address the issue of tooth wear on synchronous belt pulleys?
A: Possible causes include excessive load, excessive belt tension, poor pulley material, or inclusion of abrasive particles. Solutions include improving the design, reducing tension, using pulleys with higher hardness and surface hardening treatment, improving the environment, and implementing protective measures.


Timing belts case study


Equipment Name: 3C Inspection Equipment
Design Objective: The design objective of this equipment is to achieve precise transmission and positioning of the products for CCD vision capture and photography, thereby enabling automated inspection.
Part Application Description: In this equipment, the combination of synchronous belts and synchronous wheels plays a crucial role. Through proper installation and adjustment, the synchronous belts and wheels enable precise transmission and positioning of the products. Additionally, the fixed installation of stoppers and fixtures is important to ensure product stability during transmission. By working in synergy with the vision equipment, automated operation is achieved. The vision equipment accurately captures the position of the products and performs corresponding photography for subsequent automated inspection and analysis.

This design solution effectively integrates the use of synchronous belts, synchronous wheels, stoppers, and fixtures to ensure precise transmission and positioning of the products during inspection. Through automated operation, inspection efficiency and accuracy are significantly improved. Such a design solution can be widely applied in the field of product inspection in the 3C industry, providing reliable technical support for the realization of automated production lines and enhancement of product quality.




In conclusion, timing belts are vital for maintaining proper synchronization and efficient power transmission in a wide range of applications. By understanding their composition, types, materials, and features, you can make informed decisions when selecting the right timing belt for your specific needs. Remember to consider factors such as load capacity, operating conditions, and maintenance requirements when choosing and installing a timing belt. Regular inspection and maintenance, along with following proper installation and disassembly procedures, will help maximize the lifespan and performance of your timing belt. And finally, if you ever have any questions or encounter issues, refer to the FAQs section for quick answers and troubleshooting tips.