Most people know that an average car or truck is fitted with suspension and springs to provide a much smoother ride. These can be mechanical, pneumatic or even electric, but they are designed to ensure that your vehicle performs well, no matter the speed or road condition. Yet these primary suspension components by themselves would never be enough, and your vehicle is also equipped with a secondary system. What is this, and what should you do if you encounter a problem?
Generally speaking, the primary suspension components are designed to cope with the largest loads. When your vehicle goes over a pothole, for example, the road wheel may move through significant vertical range, and this movement will need to be addressed and dampened quickly. The shock absorber will do most of the work while the associated spring will help to regulate so that everything gets back to normal as quickly as possible.
Dealing with Vibration
Yet even if you were to drive along a perfectly flat road in a straight line, this type of system would not be enough. You would certainly feel vibrations which would feed through the wheels, move along a variety of individual components and get through to the vehicle frame.
To counter this particular challenge, engineers typically incorporate a large selection of rubber bushings. These will act as an interface between a certain component and the point to which it is attached, and will absorb most or all of that vibration at source.
For example, you will find a set of bushings at the top of the suspension strut assembly, and where it mounts to the bodywork. You will find control arm bushings mounted at either end of the said arm, which connect the wheel hub to the centre of the body, and counteract the lateral movement.
Some vehicles are equipped with a separate frame under the bonnet, designed to hold the engine, gearbox and transmission assembly. This frame is securely bolted to the body of the car and, once again, heavy-duty rubber bushings (also known as "doughnuts"), sit in between to isolate vibration and road noise.
All of these bushings are designed to last a long time, but they will inevitably begin to deteriorate and could crack. When they do so, you'll begin to notice a lot more vibration and the vehicle will feel more uncertain on the road. At this time, you will need to change the offending bushings and probably the entire set. However, make sure that you entrust this type of job to an experienced mechanic.