Suspension Bushings might be small in size, but they play a very big part of your vehicle 's suspension system. Bushings are usually made of polyurethane or rubber and they are designed to reduce friction between metal parts that come in contact with each other. This helps to isolate vibration and provide some cushioning. Because they are made of soft, flexible materials, Bushings can degrade over time and will need to be replaced. As they degrade, you'll start to notice creaks and banging coming from the wheel fenders, excess vibration and road noise, extremely loose steering and you'll start to hear the frame rattle when you go over bumps.