MOT advisory explained
“Brake pads wearing thin”
Unlike most advisories, this one has an exact number behind it. Ask for the measurement and you will know whether you have months or weeks — and whether the discs are about to join the bill.
There is still legal friction material on the pads, but not much of it. Pads wear predictably, which makes this the rare advisory where a single measurement tells you almost exactly how long you have.
Book it in the next few weeks rather than months. Running pads to the backing plate destroys the discs and doubles the bill.
Pads only, per axle, fitted. If the discs are lipped or scored they get replaced at the same time, which takes it to £180–£460 — model-by-model prices in the brake cost guide.
“Wearing thin” is not “worn out”. Four millimetres can last months of ordinary driving; two cannot. The number is the whole answer, and any garage with the wheel off can read it.
A “brake pads wearing thin” advisory means the friction material is low but still above the 1.5 mm MOT limit, so the car passes — testers usually write it between three and five millimetres. Replacing pads costs £90–£220 per axle fitted. Of 35.8 million tracked brake advisories, 9.4% later returned as a failure.
What the number actually means
A brake pad is a block of friction material bonded to a steel backing plate. New, the friction material is usually around ten to twelve millimetres thick. The MOT fails it below 1.5 mm. Everything between those two figures is the pad doing its job, and this advisory means a tester looked at yours and thought the remaining thickness was worth writing down.
- Ten to twelve millimetres — new. The figure varies by car and by pad, but it is the right ballpark for a normal road car. Everything below it is proportional wear, so a pad at six millimetres has done roughly half its life.
- Around four millimetres — the usual point of an advisory. Still comfortably legal, still braking normally, but visibly reduced. Most testers write it somewhere between three and five millimetres. At ordinary mileage this is several months away from needing anything.
- Around three millimetres — where most garages recommend replacement. Not because it is unsafe, but because it is the sensible planning moment: enough margin left to book at your convenience rather than urgently.
- Below two millimetres — weeks, not months. The wear rate does not accelerate, but the margin for error disappears, and a hard motorway journey or a heavy load can take more material than you expect.
- 1.5 millimetres — the MOT limit. Below that the car fails.
Which is why the useful question is not whether the pads are “worn” — they are always wearing — but what they measured. A garage with the wheel off reads it in seconds, and the difference between four millimetres and two is the difference between planning and hurrying.
How long you actually have
Pads wear roughly in proportion to miles and heavily by driving pattern. Town driving with constant stopping eats pads several times faster than motorway miles, which is why the same car can need pads every twenty thousand miles for one owner and fifty thousand for another. Front pads generally wear two to three times faster than rears, because the weight transfers forward every time you brake.
Which means the advisory alone cannot tell you how long you have — but the measurement plus your mileage can. If your pads are at four millimetres and you do ordinary mileage, you are looking at months. If you do high mileage in traffic, the same four millimetres is a much shorter window. Our mileage check works out your actual annual figure from the MOT record if you want to be precise about it.
Listen for the wear indicator. Most cars have one of two systems: a small metal tab that touches the disc and produces a distinctive high squeal when the pad gets low, or an electrical sensor that lights a warning on the dashboard. Both are designed to give you notice before the friction material runs out, and both mean the same thing — book it now rather than next month.
A grinding noise is a different signal entirely. That is metal backing plate against disc, and it means the pads have gone. At that point the discs are damaged regardless of how they measure.
The 1.5mm limit, and what else fails
This is one of the few brake items with a published figure. Brake pads or linings less than 1.5 mm thick are a major defect and fail the test. That number is in the inspection manual and it applies to every car, which makes it unusual — the equivalent limit for brake discs is set by the manufacturer and stamped on the disc, not published centrally.
Thickness is not the only way pads fail. The test also fails pads that are contaminated — usually with oil or brake fluid from a leaking caliper or hose — and those that are loose, missing or clearly not doing their job. A contaminated pad can measure eight millimetres and still be a failure, because oiled friction material does not grip.
The test also measures braking performance on a rolling road, and that catches something a visual check does not: imbalance. If one side of an axle brakes significantly harder than the other, the car fails regardless of how much pad is left. Uneven pad wear side to side often points at a sticking caliper rather than the pads themselves — see the caliper guide.
The practical version: ask for the millimetres on each corner, not just an average. Four different numbers tell a story that one number hides.
How often does this advisory become a failure?
This can be measured rather than guessed. Following every brake advisory forward to the same vehicle’s later tests, across 35.8 million of them, shows what actually happened.
| What happened next | Brake parts | Suspension | Tyres |
|---|---|---|---|
| Became a failure at a later test | 9.4% | 18.7% | 9.9% |
| Ignored, no action taken | 36.1% | 37.1% | 30.5% |
| Fixed | 54.4% | 44.2% | 59.6% |
| Median advisory to failure | 376–379 days — the next MOT | ||
From the DVSA MOT testing bulk dataset (Open Government Licence v3.0): 829.7 million tests and 145.1 million advisories tracked to each vehicle’s later tests, from 35,816,965 brake advisories. Defect code 1.1 covers brake components generally, not pads alone.
Brake advisories convert at half the rate of suspension — 9.4% against 18.7% — while being ignored almost exactly as often, 36.1% against 37.1%. Same neglect, half the failures. That comparison is the most useful thing in the table, and it is easy to read the wrong way.
The conversion figure measures one thing only: whether the car later failed a test. Pads rarely get that far, because the noise arrives first — the wear indicator squeals, or the grinding starts, and almost nobody drives on through a year of that. So the MOT record sees the advisory resolved.
What the record does not see is the bill. Pads run down to the backing plate destroy the discs, and that turns a £90–£220 job into £180–£460 — a repair cost rather than a test failure. For brakes, the risk of failing and the cost of waiting are two different numbers, and only one of them is in the national data.
The 54.4% fix rate is the highest of any category, but part of it is simply routine servicing: pads get changed at the next service whether or not a tester wrote anything down.
Why the discs decide what this costs
Pads alone are a cheap job. Pads and discs together cost roughly twice as much. Which one you get depends entirely on the condition of the discs, and that is worth understanding before you are asked to decide at a counter.
Discs wear as pads wear, more slowly but continuously, and they develop a lip at the outer edge where the pad does not reach. A modest lip is normal and does not prevent new pads bedding in properly. A pronounced one, or deep scoring, means a new pad cannot make full contact — and the pad wears to match the disc’s uneven surface rather than the other way round.
The honest test is measurement, not appearance. Discs have a minimum thickness stamped on them, and a disc close to that limit is replaced with the pads because it will not survive another pad life. A disc with plenty of material and only a light lip does not need replacing simply because the pads do.
Which means the question “do I need discs as well?” has a factual answer, and it is the second thing to ask after the pad measurement. If the answer comes without a number attached, ask for one.
What it costs
| Job | Price fitted | Notes |
|---|---|---|
| Pads only, one axle | £90–£220 | Front and rear are separate jobs |
| Pads and discs, one axle | £180–£460 | When discs are lipped or near minimum |
| Caliper slide clean and grease | ≈ £20 | Cheap, and it prevents uneven wear |
| Wear sensor, where fitted | Ask at the time | Must be renewed with the pads on many cars |
Independent garage prices, parts and labour. Main dealers typically charge around 50% more. Full prices by model on the brake pads and discs cost page.
Small cars with common parts sit at the bottom of the range; larger cars, premium brands and models with wear sensors that must be replaced alongside the pads sit at the top.
The slide service is worth having and worth asking about. Caliper slide pins seize with corrosion, and a seized slide makes one pad do most of the work, wearing it out early and unevenly. Cleaning and re-greasing the slides while the pads are off costs very little and prevents the fault that most often brings people back early. Some garages include it, some charge for it, and a few skip it.
Front and rear are separate jobs with separate wear rates. An advisory on the front axle is not a reason to do the rear, and a quote covering both should show separate measurements for each.
Pad quality is a genuine choice. Budget pads work, but tend to produce more dust, fade sooner under repeated hard braking and wear faster. Mid-range from a known manufacturer is the standard sensible answer, and the price difference across a set is usually smaller than the labour.
| Worked example — front pads only, family hatchback | |
|---|---|
| Pads, axle set, quality aftermarket | £45 |
| Labour — 1 h × £65 | £65 |
| Caliper slide clean and grease | £20 |
| Typical total | ≈ £130 |
Inside the £90–£220 range. Adding discs takes the same job to £180–£460 — the brake cost guide has the figure for your model.
Enter your reg — we’ll read your MOT history, decode each advisory and price it for your exact model.
What to do next
- Ask for the millimetres, corner by corner. This is the one advisory in the whole test where the threshold is published and the measurement takes seconds. Four numbers tell you a story that one average hides.
- Ask whether the discs measure within spec. The minimum is stamped on the disc, so this is a fact rather than an opinion. It is also the difference between a £90–£220 job and a £180–£460 one.
- Compare the two sides. If one pad is markedly thinner than its partner, the cause is usually a seizing caliper slide rather than the pads. Fixing the cause costs little; ignoring it wears the new set the same way.
- Ask whether the slide service is included. Some garages do it as standard, some charge separately, and a few skip it. It is the cheapest line on the whole job and the one most likely to save you a repeat visit.
Brake pad advisory FAQ
How thin is too thin for brake pads?
Below 1.5 mm of friction material the car fails its MOT. Most garages recommend replacement around 3 mm, which leaves enough margin to book the work at your convenience. New pads start at roughly ten to twelve millimetres, so a pad at 3 mm has around a quarter of its life left.
How long do brake pads last?
Anywhere from twenty thousand to fifty thousand miles, and driving pattern matters more than mileage. Constant town stopping wears pads several times faster than motorway driving. Front pads typically last a third to a half as long as rears, because weight transfers forward under braking.
What is the brake wear indicator and what does it sound like?
Two systems are common. A mechanical tab makes contact with the disc as the pad thins and produces a distinctive high-pitched squeal, usually loudest when you are not braking. An electrical sensor triggers a dashboard warning instead. Both mean the same thing: book the work now.
Can I have new pads fitted without changing the discs?
Yes, if the discs are still within their minimum thickness and not heavily scored or lipped. That is a measurement rather than an opinion, so ask for it. Fitting pads to badly worn discs gives poor braking and wears the new pads quickly, which is why the two jobs are often done together.
Why is one brake pad more worn than the other?
Usually a sticking caliper slide. If the caliper cannot move freely, one pad is pressed against the disc harder and more often than its partner, and wears out well ahead of it. Cleaning and greasing the slides is a cheap part of any pad job, and it fixes the cause rather than just the symptom.
Do brake pads fail an MOT for anything other than thickness?
Yes. Contamination with oil or brake fluid is a failure regardless of how much material remains, because oiled friction material does not grip. So is a pad that is loose or missing. The rolling-road brake test also catches imbalance between the two sides of an axle, which can fail a car with plenty of pad left.
How often does a brake advisory become an MOT failure?
Across 35.8 million tracked brake advisories, 9.4% returned as a failure at a later test, 54.4% were fixed and 36.1% were ignored — half the conversion rate of suspension despite an almost identical ignore rate. Read it carefully, though: pads usually announce themselves by squealing before a test comes round, so the cost of waiting lands as disc damage on a repair bill rather than as an MOT failure in the record.