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.
A common MOT failure is excessively worn tyres and it is amazing how many tyres we see that have worn unevenly, and prematurely. It is rarely a fault with the tyre and is usually a suspension issue.
One of the most common suspension issues we see in the workshop is ‘bush wear’. In fact, bush wear is a common MOT failure and you may have already experienced this problem in the past.
Suspension bushes are rubber mountings that link your vehicle’s suspension arm to the chassis. The rubbery material is vital for absorbing movement and vibration when travelling on the road. If all suspension components had rigid metallic links and hinges, the ride would be harsh, noisy and very uncomfortable, so these rubber bushes are vital for a smooth and enjoyable driving experience.
And, because it’s your vehicle’s suspension that holds the wheels in place, worn or soft bushes can have a detrimental effect on wheel alignment and ultimately lead to premature tyre wear.
As cars have advanced over the years, wheel alignment has become crucial for the safety of road users. Modern vehicles, with traction control and ABS, must perform to strict guidelines and tolerances to ensure road users’ safety. If the vehicle does not drive or brake correctly the ABS/TCS may not be able to prevent an accident.
So, if you notice; uneven tyre wear; or your steering wheel is not pointing straight when driving straight; or the car pulls to the left or right while driving or braking; or you hear a knocking coming from your suspension, you should take it to your garage for a suspension check and wheel alignment, as soon as possible.
Ben Grave, Mark Lawson