Chapter 3 — Section 2: Steering and suspension

Steering and suspension are the mechanical link between what the driver does and what the tyres do. Section 2 of the test exists to keep that link precise and sound. The inspection has two parts: a visual check for deterioration, leaks and perished rubber, and a physical check for play in the joints. Faults here rarely stay isolated. A worn bush can accelerate tyre wear or upset braking stability, which is why this section produces a good share of the Major and Dangerous defects recorded nationally.

01Steering linkage and ball joints

The main focus is the track-rod ends and the steering rack. The tester checks for excessive play in the ball joints by rocking the road wheels with the car over a pit or on a lift. The inspection manual doesn't give a millimetre figure, because tolerance varies by make, but any movement suggesting the ball is no longer properly seated in its socket will usually fail.

• A split or missing dust cover (gaiter) that lets dirt into the joint is a Major defect.
• Steering rack gaiters must be intact and not torn badly enough to let lubricant escape.
• Movement of the rack body against the subframe, often from perished mounting bushes, is a common fault on older cars.
• Power steering fluid leaks are inspected too: light seepage is usually noted as an advisory, a continuous drip is a fail.

02Suspension springs and mountings

Springs, whether coil, leaf or torsion bar, carry heavy vertical loads and sit exposed to road salt and moisture for years. A fractured coil spring is the most common failure, usually breaking where moisture collects at the top or bottom coil. A cracked or broken spring is a Major defect; if the break means the spring could work its way out of its seat, it's Dangerous.

• Leaf springs are checked for cracked leaves and secure U-bolts.
• Air suspension is tested for leaks and whether the compressor can hold ride height.
• Bonded rubber bushes are checked for delamination, where the rubber has come away from its metal sleeve.

03Shock absorbers and damping

Shock absorbers are mostly checked by eye and by hand rather than on a rig. The tester looks for fluid leaks: light misting is acceptable and noted as an advisory, but a leak that's reached the lower mounting is a fail. The unit must also be securely fixed. A simple bounce test on each corner is common; if the car keeps bouncing beyond a cycle or two, the damper is judged ineffective.

04Control arms, panhard rods and anti-roll bars

Wishbones and trailing arms must be free of corrosion severe enough to weaken them. Testers sometimes use a hammer test to check whether the metal has thinned to the point of losing structural strength. Anti-roll bar links, usually called droplinks, are one of the highest-volume failure items in the whole test. They're rarely as safety-critical as a worn ball joint, but a snapped link or a perished bush in it is still a Major defect.

• Anti-roll bar bushes are checked for excessive clearance.
• Panhard rods and torque arms are inspected for security and the condition of their end fittings.
• Welding repairs to these parts are generally not permitted unless the manufacturer specifically allows it, because welding can change the heat treatment of the metal.

05Wheel bearings and hub assembly

Wheel bearings are checked under Section 2 because they're part of the corner assembly, even though strictly they belong to the transmission of movement. The tester spins each wheel listening for rumbling or roughness, and checks for physical play. A small amount of play may be acceptable on older cars with adjustable taper-roller bearings, but a modern sealed unit should have next to none. Roughness or play that affects steering or braking will fail.

06Where the line falls between advisory and major

Judging a ball joint often comes down to the tester's experience with how much clearance is normal for the vehicle's age. Movement within a safe working range earns an advisory; movement that risks the joint popping out, or steering becoming imprecise, must fail. Dangerous is reserved for something likely to fail imminently, or that already has, in a way that takes steering or suspension control away from the driver, such as a detached steering rack or a snapped column universal joint.