Suspension arms, bushes and ball joints are replaced in the workshop every day. Every time a vehicle’s wheel moves up or down, and when the steering wheel is turned, these components are in use and as a result, start to wear. These components are used to connect the wheel to the chassis and suspension components, like the coil or leaf springs.
Suspension arms need to allow up and down movement of the wheel but still hold the wheel central inside the wheel arch (not allowing forward and backwards movement). So, they need to be strong, but pivot both ends. To allow the arm to pivot, ball joints and/or bushes are used.
Ball joints wear because of constant use and leads to excessive movement in the suspension components. This will lead to a rattle or knocking noise within the cabin.
Bushes also knock when perished, worn or become unbonded from their housing. They commonly fail the MOT due to excessive wear or free play which, if not rectified promptly, can cause uneven tyre wear and handling issues.
Like CV Joints, Ball joints have a rubber boot covering them to retain the lubricating grease. If this boot is split, damaged or insecure, they can fail the MOT.
Common Mot Failures
The reason these are considered an MOT failure is because the vehicle’s handling can be seriously affected and cause the car to pull left or right. So, it is vital to keep the suspension in good working order.
In addition, premature and uneven tyre wear are caused by play in the suspension and steering joints. Whenever a steering or suspension joint is replaced, the alignment must be checked/adjusted.
Some vehicles, particularly larger German manufactured ones, have several suspension arms on each wheel. They may fail on upper, lower, upper rear most etc.
Ben Grave, Mark Lawson