March 14, 2024
Motorcycle suspension system: everything you should know
The motorcycle suspension system is a crucial component of motorcycle for the riding experience and vehicle performance. While we often focus on the engine and exterior design, the suspension system also plays an indispensable role in overall performance. This article will delve into the functions, structures, tuning methods, and future development trends of motorcycle suspension system, providing a comprehensive understanding of suspension systems.
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The impact of suspension systems on handling and comfort
Basic functions of suspension systems
The primary function of the motorcycle suspension system is to connect the wheels to the vehicle body, absorbing shocks from the road to maintain the vehicle’s stability and comfort. It accomplishes this through components such as the front fork, rear shock, and swingarm.
The motorcycle suspension system not only supports and guides the wheel’s movement but also reduces vibrations caused by uneven surfaces, increasing the contact area between the tires and the ground, thereby enhancing grip.
Handling performance and comfort are the two aspects that must be balanced in motorcycle suspension system design. Handling performance refers to the vehicle’s responsiveness and stability during operation, while comfort reflects the vehicle’s shock absorption efficiency. The suspension system achieves a dynamic balance between the two by adjusting spring stiffness and damper settings.
The importance of handling performance
Improving the handling performance of a motorcycle allows riders to feel greater safety during high-speed driving and complex road conditions. The motorcycle suspension system enhances handling performance in the following ways:
- Enhancing tire grip: The suspension ensures that the tires maintain maximum contact with the ground under various road conditions, thus achieving optimal grip.
- Improving vehicle stability: A good motorcycle suspension system effectively minimizes body jolts and sways, allowing the rider to better control direction, especially when cornering at high speeds.
- Reducing riding fatigue: A comfortable ride can reduce rider fatigue, helping them stay in good mental state and maintain control during long-distance rides.
Common modern motorcycle suspension designs, such as upside-down front forks and multi-link rear suspensions, can effectively improve handling performance. Upside-down front forks lower the center of gravity of the oil tank and spring, increase rigidity, and improve compliance, ensuring a more agile response.
Enhancing comfort
Equally important to the motorcycle suspension system is its ability to enhance riding comfort. In city riding or on long trips, uneven surfaces can cause significant discomfort for riders, presenting another major challenge for the motorcycle suspension system. To ensure riding comfort, the adjustments in the suspension system mainly focus on the following aspects:
- Appropriate suspension travel: When designing a suspension system, it is essential to ensure that it has sufficient travel to cope with the impacts of complex road conditions.
- Adjustment of springs and damping: The design of the suspension system’s springs and damping should allow for adjustments based on actual riding needs. For motorcycles intended for long-distance travel, a preference for softer spring configurations is common to achieve better comfort.
With advancements in technology, the introduction of semi-active and active suspension systems also provides riders with a higher level of comfort adjustments. By using sensors to monitor road conditions in real time, the suspension characteristics can be dynamically adjusted, making the riding experience smoother.
Internal structure of the suspension system
Components of the motorcycle suspension system
The motorcycle suspension system mainly consists of three parts: the suspension mechanism, springs, and dampers. These three work in unison to realize the overall performance of the suspension system.
- Suspension mechanism: This is the crucial structure that connects the wheels to the vehicle and is responsible for guiding the wheel’s movement. Common suspension structures include conventional upright suspensions, upside-down suspensions, and multi-link suspensions. Each design has its unique advantages and applicable scenarios.
- Springs: Springs are the main components that support the vehicle’s weight. When loaded, the springs compress, allowing the vehicle to absorb road impacts. The stiffness (spring constant) and length of the springs are critical factors affecting comfort and handling, and they are usually adjusted based on the rider’s weight and riding habits.
- Dampers: The role of dampers is to control the recovery speed of the springs, ensuring that the vehicle stabilizes quickly after being subjected to impacts. Modern motorcycle suspension systems typically come equipped with adjustable dampers to adapt to different road conditions and rider needs.
Upper/lower suspension design
Another important aspect of suspension design is upper suspension and lower suspension. Based on the location of the engine mount, we can divide suspension into upper and lower suspension.
- Upper suspension: The engine mount is located above the engine, providing good anti-twist rigidity and relatively excellent shock absorption, resulting in a lighter feel during riding. It is suitable for longer rides, but high-speed cornering may compromise stability due to a higher center of gravity.
- Lower Suspension: The engine mount is located below the engine, resulting in a lower center of gravity that provides good stability during high-speed travel and cornering. This design is especially suitable for riders who favor curves. However, it tends to have weaker anti-twist rigidity and may perform less effectively under significant impacts compared to upper suspension.
Unsprung mass and overall performance
Unsprung mass refers to the mass below the suspension system’s springs, including the tires, wheels, and related components. Reducing unsprung mass helps improve the suspension’s response speed and sensitivity. When discussing the performance of suspension systems, comparisons often occur between sprung mass (body center of gravity) and unsprung mass in search of a more suitable weight ratio.
The lower the unsprung mass, the more sensitive the suspension response: it rebounds more quickly, resulting in better tire performance on the ground.
Efforts to reduce unsprung mass typically involve using lightweight materials (such as forged aluminum or carbon fiber), which not only enhance performance but also reduce the inertia effects of the motorcycle during acceleration.
Comparison of positive and negative damping
The front suspension system of motorcycles usually includes both conventional (positive) and upside-down (negative) damping, and the majority of riders can distinguish the specific advantages and disadvantages of these two designs.
Conventional front fork (positive damping)
As a traditional suspension design, conventional front forks have a relatively simple structure that is easy to manufacture and maintain. The main advantages and disadvantages are as follows:
- Advantages:Lower production costs and ease of maintenance; suitable for everyday use with strong adaptability.
- Disadvantages: Weaker rigidity and relatively lower stability during travel; insufficient control effectiveness during high-speed driving or sharp turns, easily leading to a front-heavy situation.
Upside-down front fork (negative damping)
Upside-down front forks are standard equipment for modern high-performance motorcycles, designed to enhance overall performance by altering structural principles.
- Advantages: Increased rigidity, faster compression and rebound response, enhancing vehicle stability while cornering; lighter unsprung mass, resulting in more sensitive suspension responses.
- Disadvantages: Relatively higher manufacturing costs and more complex maintenance; might be overly designed for standard motorcycles, affecting the everyday riding experience.
In summary, upside-down front forks are suitable for performance-seeking riders, while conventional front forks are more friendly to everyday riders.
Exploring non-traditional suspension systems
In recent years, motorcycle designs have gradually introduced some non-traditional motorcycle suspension systems to meet different performance and comfort needs. Here are several representative non-traditional suspension designs:
- HOSSACK suspension system
The HOSSACK system was designed by Scottish inventor Norman Hossack in the 1970s. This structure utilizes double A-arms and connecting rods to effectively allow independent steering and shock absorption, revealing its superior handling performance under complex road conditions.
- TELELEVER suspension
TELELEVER is an innovative system developed by BMW in 1993, characterized by motorcycle shock absorbers connected via a link, ensuring the separation of steering and shock absorption, effectively enhancing ride stability and comfort.
- DOULEVER suspension
As an evolution of TELELEVER, DOULEVER is specially designed to ensure higher levels of torsional resistance and comfort performance, adapting better to various dynamic road conditions.
- TESI suspension
The Tesi system reconfigures the front fork into a swingarm design, steering through the wheel hub, enhancing the stability of the steering system and reducing front-loading caused by braking, suitable for high-performance motorcycles.
- RADD Suspension
The RADD system adopts a single front swingarm design, reducing tire load and improving vehicle stability, providing riders with a new driving experience.
- TLAD suspension
TLAD, which stands for Trailing Link & Anti Dive Suspension, is designed to reduce front loading when braking and is widely used in lightweight motorcycles in Italy ( get more about the top 10 electric motorcycle manufacturers in Europe).
Conclusion
Motorcycle suspension systems are essential factors influencing riding performance and experience. Understanding the basic principles and components of suspension design will help riders make informed decisions when selecting, modifying, and maintaining their motorcycles.
With ongoing technological advancements, future motorcycle suspension systems are expected to achieve a more perfect balance between comfort and handling, offering riders unprecedented riding pleasure.
FAQ
How to understand the parameters of front dampers?
Travel, tube diameter, damping, preload adjustment, and spring coefficient are crucial parameters. Travel determines the movement range of the suspension system, the tube diameter relates to rigidity, while damping, preload, and spring coefficient affect overall handling performance.
What are oil/gas separation and oil/gas mixed damping?
Oil/gas mixed designs are simple and inexpensive but prone to bubble formation, whereas oil/gas separation designs ensure damping stability, making them suitable for high-performance motorcycles.
What are the benefits of external gas tanks?
External gas tanks provide independent space to accommodate gas and damping oil, enhancing damping effects and maintaining suspension performance stability.
What are the characteristics of twin-tube dampers?
Twin-tube designs generate less resistance during use, making them suitable for a broader adjustment range and commonly found in high-end racing motorcycles.
How to conduct preload adjustments?
Preload adjustment is done on the damping spring by observing the set ring and the current spring situation to accommodate different riders' weights and needs.
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Willow is a materials engineer with a Master’s degree in Materials Science and Engineering, specializing in lithium-ion battery materials and energy storage technologies.
Her work focuses on EV battery swapping solutions, battery innovation, and new energy industry trends, aiming to translate research insights into practical applications for sustainable transportation.
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