Knocks and Clunks: Diagnosing Worn Suspension Parts

October 25, 2026

Knocks, clunks and rattles from underneath the car are some of the hardest noises to pin down. They come and go with the road surface, the speed and the way the car is loaded. Most of them come from a small group of suspension parts, though, and knowing what each one does makes diagnosis much easier.

What the suspension does

The suspension keeps the tyres in contact with the road, absorbs bumps and controls how the car leans, dives and squats. It is made up of springs and dampers, arms and links that locate the wheels, and rubber bushes that let those parts move while soaking up vibration. When any of these wear, the car can become noisy, vague to drive and less stable in an emergency.

Drop links

Drop links connect the anti-roll bar to the suspension. They have small ball joints at each end that wear over time.

Typical symptoms: a light knock or rattle over small bumps, speed humps and broken surfaces, especially at low speed. Worn drop links are one of the most common sources of suspension noise and are usually inexpensive to replace.

Anti-roll bar bushes

These rubber bushes hold the anti-roll bar to the car's body or subframe.

Typical symptoms: a creak or clunk over bumps, or when turning on and off driveways. Noise in cold or wet weather is common when the rubber has hardened.

Control arms and bushes

The lower control arms, sometimes called wishbones, locate the wheel. They pivot on rubber bushes and are joined to the hub by a ball joint.

Typical symptoms: a clunk when braking or accelerating, wandering on the motorway, uneven tyre wear and a vague feel through the steering. A worn ball joint can knock over bumps and is a safety issue, as a separated ball joint means the wheel is no longer properly held.

Top mounts and bearings

On cars with MacPherson strut front suspension, the strut is held at the top by a rubber mount, often with a bearing that lets the strut turn with the steering.

Typical symptoms: a knock or creak when turning the steering on full lock, a clonk over larger bumps, or a feeling of notchiness in the steering.

Springs and dampers

Coil springs can snap, often at the bottom coil, especially on older cars or after hitting a pothole. Dampers, often called shock absorbers, wear gradually.

Typical symptoms: a sudden loud bang or a car sitting lower on one corner points to a broken spring. A bouncy ride, leaking dampers and the car diving heavily under braking point to worn dampers. Springs and dampers should be replaced in axle pairs.

How to narrow it down

Note when the noise happens: over small bumps, large bumps, when braking, or when steering.
With the car safely supported, check for play by levering arms and links gently, and look for split or perished rubber.
Check the anti-roll bar, exhaust mounts and heat shields too, as loose parts can mimic suspension knocks.
If you are unsure, a garage can check the suspension on a ramp in a few minutes.

Worn ball joints, damaged springs, excessive play and leaking dampers are all MOT failure points, so it pays to fix them early.

Why genuine suspension parts restore factory handling

The way a car rides and handles depends on the precise shape of each arm and the stiffness of each bush. Manufacturers tune these to balance comfort, noise, grip and stability. Genuine parts are made to the same specification, so the car feels as it did when new. Cheaper parts may use softer or harder rubber, or ball joints that wear faster, changing the way the car steers and brakes.

Suspension parts often vary by engine, trim and whether the car has sports or standard suspension. Use your VIN to confirm the part number. Our guides to using your VIN and reading exploded parts diagrams explain how, including the one-use bolts that should be replaced at the same time.

A note on alignment

After replacing arms, bushes or steering parts, have the wheel alignment checked. Incorrect alignment can make the car pull and wear the tyres quickly, undoing the benefit of the new parts.