When it comes to suspension systems, the pivoting connections used to locate and rotate components play a crucial role. In this module, we will discuss the different types of suspension joints and the factors to consider when selecting them.
Polymer Bushings: Balancing Comfort and Performance
Polymer bushings are commonly used in OEM suspension systems to reduce noise, vibration, and harshness (NVH). These bushings are made of rubber or polyurethane and offer a certain degree of compliance, which helps to absorb shock loadings and vibrations. While this is great for road cars, the high compliance of polymer bushings is not suitable for motorsport, where higher loads are applied.
The downside of this compliance is that it can cause suspension geometry to become less constant, which affects the responsiveness of the chassis to driver inputs. Bushing stiffness can be tuned precisely to balance comfort and performance in high-performance road cars. In some cases, replacing factory bushings with aftermarket polyurethane bushings can reduce compliance and improve performance.
However, upgrading to aftermarket bushings can compromise NVH, making it a better solution for cars that are used for daily driving and occasional competition use. It’s also essential to note that the position of the bushing when the mountings are tightened is crucial, and it’s generally best to tighten them when the car is at its static ride height position to minimize stress to the bushings.
Spherical Bearings: Higher Compliance and Crisper Response
Spherical bearings, also known as rod ends, are a more rigid alternative to polymer bushings. They offer reduced compliance and crisper response when used in components like suspension arms and damper mounts. However, they also contribute to a lot more NVH and have a shorter lifespan than polymer bushings.
Another downside of spherical bearings is that they should not be placed in bending, where forces are not aligned with the part. In such cases, using threaded rod ends can cause bending forces that can lead to failure. When bending forces are present in suspension components, it’s essential to upgrade to a larger or stronger rod end to ensure reliable performance.
Q: What are the advantages of polymer bushings? A: Polymer bushings reduce noise, vibration, and harshness in OEM suspension systems, making the ride more comfortable for occupants.
Q: What are the downsides of spherical bearings? A: Spherical bearings offer higher compliance and crisper response, but they also contribute to more NVH and have a shorter lifespan than polymer bushings.
Q: Can threaded rod ends be used in suspension components? A: Threaded rod ends should be avoided in components that have bending forces present as they can cause stress concentrations that lead to failure.
- “Suspension Bushings: Polyurethane vs. Rubber” by Matt Cramer, DIYAutoTune.com Link: https://www.diyautotune.com/support/tech/tuning-articles/suspension-bushings-polyurethane-vs-rubber/
- “Choosing The Right Suspension Bushings” by Steve Temple, HotRod.com Link: https://www.hotrod.com/articles/choosing-the-right-suspension-bushings/
- “How to Avoid Suspension Failures in High-Performance Cars” by Paul Van Valkenburg, HotRod.com Link: https://www.hotrod.com/articles/how-to-avoid-suspension-failures-in-high-performance-cars/