Suspension arm bush deteriorated or worn: what the MOT advisory means
A suspension bush MOT advisory means the rubber mount where a suspension arm bolts to the car is cracked, perished or showing some wear, but there isn't enough movement to fail it. The car is fine to drive. Bushes wear gradually, so plan to replace it in the next few months, and sooner if you start hearing clunks or the car wanders on the motorway.
What a suspension bush does
Suspension arms (wishbones) hold each wheel in place and let it move up and down. Where an arm bolts to the body or subframe, there's a bush: a metal sleeve bonded into rubber. The rubber soaks up vibration and lets the arm pivot without metal knocking on metal.
Rubber doesn't last forever. Heat, oil, road salt and years of flexing make it crack and go soft. Eventually the inner sleeve starts moving around inside the outer one, and that's when you feel and hear it.
When it becomes an MOT fail
The MOT manual puts pins, bushes and suspension joints under section 5.3.4:
| What the tester finds | Category |
|---|---|
| Suspension joint dust cover severely deteriorated | Minor |
| Dust cover missing, or no longer keeps dirt out | Major (fail) |
| Pin, bush, joint or bearing excessively worn | Major (fail) |
| Pin, bush, joint or bearing likely to become detached | Dangerous |
"Excessively worn" has numbers behind it. The manual gives a guide of more than 2mm of play for a 12mm pin, more than 3mm for a 25mm pin, or 10% of the diameter for anything bigger. Testers check by levering gently with a bar while watching the joint.
So the advisory wordings, such as "bush deteriorated" or "pin or bush worn but not resulting in excessive movement", mean the tester could see cracking or a little movement, but it was under that line.
Symptoms of worn bushes
- A clunk or knock over speed bumps, potholes or when pulling away.
- The car wandering or tramlining at motorway speeds.
- Steering that feels vague, or a pull to one side under braking.
- Tyres wearing on the inside or outside edge, because the wheel angle shifts.
- Tracking that a tyre shop can't get to stay in spec.
Replace the bush or the whole arm?
On a lot of modern cars, a complete lower arm with new bushes and a new ball joint costs not much more than the bushes alone. Fitting a whole arm is usually quicker, because pressing old bushes out of an arm takes time and the right tools.
| Option | Rough price at an independent garage |
|---|---|
| Single bush pressed into the existing arm | £80 to £200 |
| Complete arm with new bushes and ball joint, per side | £100 to £250 |
| Wheel alignment afterwards | £40 to £80 |
Get the wheel alignment checked after any arm or bush job, because changing these parts moves the wheel angles slightly.
Some people upgrade to polyurethane bushes. They last longer but can make the ride a little firmer and transmit more noise. For an everyday car, a good-quality rubber bush or complete arm is normally the simplest choice.
Is it a DIY job?
Swapping a complete arm is within reach of a confident DIYer with axle stands, a torque wrench and patience for seized bolts. Pressing bushes needs a press or a bush tool kit. One detail people get wrong: bush bolts should be tightened with the car's weight on the wheels, at normal ride height. Tighten them with the suspension hanging and the bush is twisted all the time, which shortens its life.
What to do now
If there's no noise and the car drives straight, keep an eye on it and have it rechecked at the next service. If you're hearing knocks, also look at the anti-roll bar links, which are cheaper and wear out more often. The drop link guide covers those.
Tyres wearing on the edge as well? Read the tyre advisory guide, or put your full result through the MOT advisory decoder.
Got more than one advisory?
Paste your whole MOT result into the decoder. It explains every line, sorts them by urgency and adds up a rough repair budget.
Decode my MOT