How these systems affect roadworthiness, tyre wear and vehicle behaviour, and when physical inspection is appropriate.
These systems overlap, but they are not interchangeable services
Brakes slow the vehicle, suspension controls wheel/body movement, and alignment describes wheel geometry. A pull, vibration or unusual tyre wear can involve more than one system, so diagnosis should come before buying an alignment or replacing tyres.
Brake clues
Grinding, scraping, vibration under braking, warning lamps, unusual pedal travel or pulling deserve inspection. Pad and disc wear are not accurately judged from mileage alone because vehicle weight, driving conditions and usage vary.
Suspension clues
Knocks, clunks, excessive bouncing, instability, uneven ride height or irregular tyre wear can be associated with worn or damaged suspension. These symptoms are not proof of a particular failed component.
Alignment clues
One-edge tyre wear, an off-centre steering wheel or persistent pull can justify a geometry check, but tyre pressure, road camber, damaged tyres and suspension faults can produce similar symptoms. Ask for before-and-after measurements if alignment is adjusted.
Do not confuse alignment with balancing
Wheel balancing addresses uneven rotating mass and is commonly investigated for speed-related vibration. It does not change wheel geometry. Selling both automatically without diagnosis is not a substitute for identifying the cause.
What to do next
Use this guide to prepare and ask better questions, not as a remote diagnosis. If a safety-critical defect is suspected, avoid unnecessary driving and arrange a competent physical inspection.
Sources and review
Reviewed 2026-08-29 · DVSA MOT inspection manual · GOV.UK roadworthiness guidance