Making the distinction | What are the types of Bushings?

Bushings as Plain Bearings

Bushings in industrial contexts are found in heavy duty applications,  which are simply large scale tasks that require lots of energy to carry out. Bushings are usually housed in a durable metal shell that can be mounted to machinery. The bushing is also a surface where the shaft can rotate with little to no friction. This frictionless behavior is desired for maximum rotary motion. Bushings are connected to shafts, and these shafts are made with incredibly resilient metals like stainless steel or steel alloys. Shafts are further reinforced with a chromium "journal" where the bushing surface makes contact with the shaft. This ensures that operations will not wear down an expensive component like the shaft. Additionally, the bushing is also made out of a soft metal called Babbitt, which allows the bushing to wear down first. The soft metal surface of bushings is also capable of absorbing invasive materials, negating some maintenance needs if operation conditions are dirty. This makes bushings ideal as a cheap replacement since its secondary role is a sacrificial one.

Rubber Bushings in Automotive

Automotive bushings have a very different purpose when compared to plain bearing bushings. Plain bearing bushings allow sliding movement between parts with reduced friction. Automotive bushings on the other hand are designed to limit sliding movement using rubber and other elastic materials to spring back parts to their original position. There is almost no friction between the bushing and its connected parts, and rotary motions will instead cause the bushing to twist the rubber element along with the shaft. Additionally, the properties of rubber make it ideal for car suspension and a smoother driving experience. The bushing serves as a cushioning layer between the metal components. For example, the control arm, which helps connect the chassis to the wheel, is subject to vibrations, and noise produced from the car itself. The rubber bushing deforms, and resist external motion caused by vibrations to an almost spring-like effect. Rubber bushings trades handling experience for a comfortable experience, therefore the hardness or softness of the bushing's elastic material determines the balance between motion resistance and control over the vehicle.

Automotive bushings are not made only from rubber or synthetic rubber. There are Polyurethane bushings that serve as a "tighter" alternative in suspension systems for more impactful driving experience. Polyurethane is more resilient and more temperature resistant than rubber. The chemical makeup of it material makes polyurethane much harder to compress - this material has less spring and softness, and consequently produces more noise, and vibrations could affect the components. Its notably squeakier, and may require periodic greasing where rubber does not. Though the advantages of specific bushing materials can vary, there are still no clear winners in this competition. It really comes down to personal preference to decide whether a specific kind of rubber bushing would suit your driving needs.

Both rubber and polyurethane aren't specifically designed to be sacrifical components like plain bearing bushings, but they are expected to wear down eventually if not serviced routinely, putting connected parts at risk. Periodic maintenance and check-ups will help diagnose if a bushing needs to be replaced in your vehicle. Rubber is very prone to damage from outside elements, and will likely be replaced often. Polyurethane may not as cheap as rubber but can last for a vehicle's entire lifetime if the owner keeps up with periodic lubrication. Safest bet is to rely on the Original Equipment Manufacturer bushings (OEM) if a vehicle's intended performance is desired.