MOT advisory explained
“Suspension component corroded but not seriously weakened”
The mildest line in the suspension section, and one of the vaguest. Testers mostly use it for a rusty rear axle beam, or as shorthand for an underside that is rusty all over. Almost none of them come back as failures.
Something in the suspension is rusty and still strong. The tester used the general term because the part had no name of its own on the testing system, or because the rust was everywhere and no single part stood out.
Only 0.4% fail under the same wording at the next test, the lowest of any suspension advisory we track. That figure is flattered by the vague name, so the fairer one is 2.5%, the share that fail on any corroded suspension part. It is still very low.
This line is background. If the same certificate lists corroded brake pipes, that is the one to spend money on. Same rust, far higher failure rate, and a part that matters more.
A “suspension component corroded but not seriously weakened” advisory means the tester saw rust on part of the suspension, most often the rear axle beam, and judged it still strong, so the car passes. No repair is needed. According to DVSA MOT data analysed by PriceMyRepair, only 0.4% of 282,271 such advisories failed under the same wording at the next test, and 2.5% failed on any corroded suspension component.
What testers use this wording for
Mostly the rear axle. The note added most often is “axle”, 65,877 times, and “rear axle”, “axle beam” and “beam axle” are all in the top eight. Many small and medium cars have a single steel beam across the back that carries both rear wheels. It is a big, bare, exposed piece of steel and it goes brown early. The testing system has no line for it, so it is filed here.
Sometimes everything. The second most common note is “all”, and “front and rear” and “all components” appear too. In those cases the tester is not pointing at one part. They are recording that the whole underside has surface rust, which on a car in its teens is simply true.
What it is not. It is not a finding about the body of the car. Rust in the structure near where the suspension bolts on has its own, much more serious line. This one is about the suspension parts themselves, which are thick and replaceable.
Will it fail next year?
282,271 of these advisories were followed to the same vehicle’s next MOT.
| What happened at the next test | Share |
|---|---|
| Failed on the same component | 0.4% |
| Failed on anything under defect 5.3.3 | 2.5% |
| Same advisory recorded again | 27.4% |
According to DVSA MOT data analysed by PriceMyRepair: 282,271 advisories followed to the same vehicle’s next test. Rows can overlap.
Read the first two rows together. A failure only counts against the same component if the next tester also writes “suspension component”, and at the fail stage they name the part. So the first row is close to zero almost by construction.
The second row has no such problem, and at 2.5% it is among the lowest in the table below. More than a quarter of these advisories are written again the following year. This is a line that stays on a car for the rest of its life without ever becoming anything.
| Advisory wording | Fails on same part | Fails under same code | Advised again | Followed |
|---|---|---|---|---|
| Suspension component mounting prescribed area is corroded | 10.2% | 12.4% | 24.2% | 1,521,106 |
| Coil spring corroded | 5.0% | 5.0% | 39.1% | 4,780,118 |
| Suspension arm corroded | 3.0% | 4.6% | 35.7% | 1,384,389 |
| Sub-frame corroded | 2.0% | 3.7% | 39.8% | 2,445,675 |
| Macpherson strut corroded | 1.6% | 3.3% | 22.5% | 370,013 |
| Anti-roll bar corroded | 1.3% | 2.3% | 23.0% | 330,897 |
| Suspension component corroded | 0.4% | 2.5% | 27.4% | 282,271 |
There are too few cases on cars under seven years old to report. From 7–9 years the advisory rises about tenfold, to 6.4 per 1,000 tests at 20 years and over. The same-wording failure rate in the third column never gets above 0.5%.
| Age of car | Per 1,000 tests | Fails on same part | Followed |
|---|---|---|---|
| 7–9 years | 0.6 | 0.2% | 24,580 |
| 10–12 years | 2.2 | 0.4% | 63,219 |
| 13–15 years | 4.3 | 0.5% | 86,185 |
| 16–19 years | 6.6 | 0.4% | 75,518 |
| 20 years and over | 6.4 | 0.4% | 26,127 |
Axle beams do eventually rust through, usually at the spring seats or where the trailing arms are welded on. It takes a very long time, and by then the tester’s note will have changed from “corroded” to “heavily corroded” and then to a different, named line.
If you plan to keep the car for many more years, having the beam cleaned and coated once is cheap insurance. If not, this advisory asks nothing of you.
Look at the beam near the spring seats if you are buying a car with this on its history. Surface rust is fine. Swollen, layered rust at a weld is a reason to negotiate.
Exact wording on your certificate
There are two general versions, one for rust and one for damage. Both mean a part the system has no specific name for.
| Line on the certificate | Result | Code |
|---|---|---|
| Suspension component corroded but not seriously weakened | Advisory — pass | 5.3.3 (b) (i) |
| Suspension component damaged but not seriously weakened | Advisory — pass | 5.3.3 (b) (i) |
| Suspension component corroded and seriously weakened | Major — fail | 5.3.3 (b) (i) |
The positions are unlike any other suspension advisory. Nearly half say just “rear”, with no side, because an axle beam does not have a side. Almost three in ten have no position at all, which fits the cases where the tester meant the whole underside.
| Position written by the tester | Share of all instances |
|---|---|
| Rear | 46% |
| No position recorded | 30% |
| Front | 11% |
| Offside rear | 3% |
| Nearside rear | 3% |
| Offside front | 2% |
From 836,212 recorded instances. Testers can add their own note after the standard wording. The most common on this advisory: “axle” (65,877), “all” (38,207), “rear axle” (23,812), “axle beam” (18,714), “both sides” (14,928), “front and rear” (14,748), “shock absorber” (13,170), “beam axle” (9,900).
Is there anything to pay for?
Not at this stage. Surface rust on a suspension component is not repaired, and we do not publish a price for treating it because garages vary too much. If a specific part is later named and does need replacing, the suspension repair cost page has prices by component and model.
Can I still drive with this advisory?
There is nothing to feel or hear. The MOT each year is the inspection this needs, and the tester will change the wording if the rust starts to matter.
Enter your reg to see how many years running this line has appeared on your car, and whether the tester’s note has changed.
Which cars get this advisory most?
The average vehicle gets this advisory on 2.0 of every 1,000 tests. The models below get it three to four times as often.
| Model | Per 1,000 tests | Vs all cars | Tests |
|---|---|---|---|
| Toyota Avensis | 9 | 4.2× | 878,561 |
| Toyota Corolla | 7 | 3.5× | 1,166,652 |
| Mazda 6 | 7 | 3.5× | 728,629 |
| Fiat Panda | 7 | 3.4× | 1,004,369 |
| Mazda 3 | 7 | 3.2× | 1,145,262 |
| Fiat 500 | 6 | 3.0× | 3,224,134 |
| Suzuki Alto | 6 | 3.0× | 556,815 |
| Ford Ka | 6 | 2.9× | 2,120,213 |
| Mazda MX-5 | 6 | 2.7× | 962,840 |
| Peugeot 107 | 5 | 2.6× | 1,292,695 |
Model families are grouped by the first word of the DVSA model name, so “Transit” covers every Transit variant. Only models with at least 60,000 tests are ranked.
Two groups share the list. Toyotas and Mazdas take five places, led by the Toyota Avensis at 4.2 times the average. The same cars lead our figures for corroded suspension arms, and the explanation is the same: they keep running long enough for the underside to rust while the rest of the car is still fine.
The rest are small cars with a beam axle at the back: the Fiat Panda, Fiat 500, Suzuki Alto, Ford Ka and Peugeot 107. On these the advisory almost always means the rear beam.
What to do next
- Check the tester’s note. The online MOT history shows any text added after the standard wording. “Axle” or “all” tells you which kind of advisory you have.
- Sort the other corrosion lines first. Brake pipes and anything mentioning a mounting or the vehicle structure come before this.
- Decide how long you are keeping the car. For another ten years, have the rear beam cleaned and coated. For another three, leave it.
- Watch the wording, not the rust. “Heavily”, “flaking” or a new named line next year is the signal to act.
Suspension component corroded advisory FAQ
What does suspension component corroded but not seriously weakened mean?
Part of the suspension is rusty but still strong. Testers use this general wording when the part has no name of its own on the system, most often the rear axle beam, or when the whole underside has surface rust.
Which component is it?
Check the tester’s note on the online MOT history. In DVSA records the most common notes on this advisory are “axle” and “all”, meaning the rear axle beam or everything underneath.
Will it fail the next MOT?
Very unlikely. According to DVSA MOT data analysed by PriceMyRepair, 2.5% of 282,271 such advisories were followed by a failure on any corroded suspension component at the next test, and 27.4% were simply advised again.
Does it need repairing, and what does it cost?
No repair is needed while the metal is sound, so there is no cost at this stage. If a part is later named and has to be replaced, the price depends on the part and the model. Any figures we publish are estimates and final quotes come from garages.
Is it safe to drive?
Yes. A component that is corroded but not weakened is as strong as it needs to be, which is why the car passed. It has no effect on how the car drives.
Which cars get this advisory most?
The Toyota Avensis, Toyota Corolla and Mazda 6, at three to four times the average rate, along with small cars that have a rear beam axle such as the Fiat Panda and Fiat 500.
How these figures were calculated. According to DVSA MOT data analysed by PriceMyRepair, from the DVSA anonymised MOT test results (Open Government Licence v3.0): 350,943,111 tests. This advisory was recorded 836,212 times; 282,271 of those were followed to the same vehicle’s next test between 180 and 730 days later. “Fails on the same part” means a failure at that next test under the same defect code and naming the same component, on either side of the vehicle. Testers do not always name a component the same way twice, so the figure is a floor. Method and how to cite.