If you’re into motorsport or have a passion for cars, you’ve likely heard the term “suspension travel” before. But what does it actually mean, and how does it affect your car’s performance? In this article, we’ll delve into suspension travel and its relationship with motion ratio, which is crucial for a proper understanding of suspension setups.
Understanding Suspension Travel
Simply put, suspension travel refers to how far a component of the suspension can move over the full extent of its movement range. In most cases, we’re interested in the vertical wheel travel, which is the distance that the wheel can travel from full droop to full compression. However, suspension travel can also refer to any other part of the suspension we might be interested in.
Factors Affecting Suspension Travel
There are many factors that go into deciding how much suspension travel we need. Two of the most important and interrelated ones are the required stiffness of the suspension we’re working with and the roughness of the surface that the vehicle is running on. These factors will be discussed in detail later in the course.
Suspension Travel in Different Applications
The required suspension travel varies greatly depending on the application. For instance, a stadium truck running on rough terrain needs a large amount of vertical wheel travel to absorb the energy of a landing and reduce the forces involved. On the other hand, a high downforce single-seater running on a smooth surface requires less travel to keep things like camber, caster, and toe within suitable limits as the car negotiates the circuit.
Compression vs. Rebound Travel
Another important aspect of suspension travel is how much of the travel is available in compression versus rebound. A sensible starting point is to allow for approximately 2/3 of the available travel in compression and 1/3 in rebound. Having the majority of our suspension travel available on compression allows the suspension to absorb undulations in the road surface, while the rebound travel is there to keep the tires in contact with the road as the chassis heaves, rolls, and pitches.
Understanding Motion Ratio
Motion ratio is closely related to suspension travel and describes how much one component moves relative to the other when they’re linked together. We’re interested in the motion ratio between a number of different elements, but the most common is between the wheel and spring and damper assembly. In almost all cases, this ratio will not be 1:1, and the value of the motion ratio will generally vary as the suspension moves through its travel.
The Importance of Wheel Rate
When comparing spring rates between different cars, it’s important to understand that the motion ratio between the wheel and the spring isn’t identical. We care about the effective spring rate at the wheel, which is generally referred to as the wheel rate. By using the motion ratio, we can calculate the wheel rate so we can make more relevant comparisons between cars with different suspension systems.
FAQ
Q: What is suspension travel?
A: Suspension travel refers to how far a component of the suspension can move over the full extent of its movement range.
Q: How does suspension travel affect a car’s performance?
A: Suspension travel affects a car’s performance by absorbing energy, reducing forces, and keeping the tires in contact with the road.
Q: What is motion ratio?
A: Motion ratio describes how much one component moves relative to the other when they’re linked together.
Q: What is wheel rate?
A: Wheel rate is the effective spring rate at the wheel, which takes into account the motion ratio between the wheel and the spring.
Conclusion
In conclusion, suspension travel and motion ratio are crucial aspects of suspension design and tuning that can greatly affect a car’s performance. The required suspension travel varies depending on the application, and a proper understanding of motion ratio is necessary for comparing spring rates between different cars. By optimizing suspension travel and motion ratio, you can improve your car’s handling and performance on the road or track.
Sources:
- Suspension Travel: What Is It and How Does It Affect Your Car’s Performance? – https://www.autosimple.com/suspension-travel-what-is-it-and-how-does-it-affect-your-cars-performance/
- The Importance of Motion Ratio in Suspension Design – https://www.nolimitmotorsport.com/blog/the-importance-of-motion-ratio-in-suspension-design/
- How to Calculate Wheel Rate: A Simple Guide for Racing Suspension – https://www.speedwaymotors.com/the-toolbox/how-to-calculate-wheel-rate/31488
