MOT defect file
Suspension arm bush worn
Last updated
Quick answer
A rubber suspension bush is deteriorating. It can cause knocking, uneven tyre wear and less precise steering as it worsens.
- Typical cost
- £160–£300
- DIY viability
- Possible with care
What you might notice
- A dull knock or clonk from one corner over speed bumps and drain covers, usually worse when the car is cold
- Steering that wanders on the motorway and needs constant small corrections
- Uneven wear on the inner or outer edge of a front tyre, because the geometry shifts under load
- Nothing at all in many cases — the tester finds it with a pry bar on a ramp, applying a load you cannot reproduce by driving
What causes it
- Age and heat: the rubber perishes, cracks and eventually separates from its metal sleeve
- Pothole and kerb impacts tearing the bonded rubber internally
- An oil or power steering leak dripping onto the bush and softening the rubber
- Salt corrosion at the outer sleeve, particularly on cars that have spent winters on treated roads
Advisory or failure?
Grading follows how much movement there is. A bush that is slightly worn or beginning to perish is a minor defect — recorded on the certificate but not a failure — and early deterioration is often noted as an advisory instead. Once there is excessive movement in the joint it is a major defect and the car fails. Where the wear is bad enough that the arm could become detached, or where it affects the vehicle's steering or stability, the grading is dangerous. A minor defect here is still worth acting on: it means the item is on its way out, not that it is fine.
Can you fix it yourself?
Possible with care
Two very different jobs share this name. Fitting a complete control arm with the bushes already pressed in is a bolt-off, bolt-on job for anyone with axle stands, a torque wrench and a ball joint separator. Pressing new bushes into the existing arm needs a hydraulic press or a purpose-made puller and is not realistic on a driveway. Either way there is one trap that catches people out: bolts through suspension bushes must be tightened with the car at normal ride height, not hanging on the stands, or the bush is permanently preloaded and will tear itself apart within months. Have the tracking checked afterwards.
What it costs
A complete lower arm for a common hatchback is £40 to £90 in parts, with around an hour and a half of labour per side, so labour is the larger share. Doing both sides together — usually sensible, since they age at the same rate — plus a four-wheel alignment takes you to the top of the band. Seized or corroded subframe bolts are the main source of unplanned labour, and on some cars the bush is only supplied pressed into the subframe, which is a considerably bigger job.
What happens if you ignore it
A perished bush rarely leaves you stranded, but it lets the wheel move out of its designed position under braking and cornering, so the car steers least accurately exactly when it matters most. The steady cost is tyres — a wheel that cannot hold its alignment will scrub the inner edge off a front tyre in a few thousand miles. Left long enough the rubber separates entirely from its sleeve, the arm starts knocking against its mounting, and the wear spreads to the ball joint and the subframe around it.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
Check the full MOT history for any UK registration.