The short answer
Tread depth is the tyre note the MOT writes most. On cars aged 10 to 14, nearly 1 in 5 first tests (18.1% of 44,980,002 tests, 2021 to 2025) recorded a tread-depth advisory: the tyre passed, but the tester noted it was getting close to the limit. The share is lower on younger cars and climbs with age, then eases slightly on the oldest. Tears in the tyre structure are the second most common note and keep rising with age. Cuts and bulges are rarer and, if anything, slightly less common on older cars.
An advisory is a warning, not a fail. GOV.UK describes advisories as problems to monitor or fix in the future. On tyres the future tends to arrive in winter, when tread matters most. If a car you own or are about to buy carries a tyre advisory on its MOT history, check the tyres this week rather than at the next test.
What the data shows
The table is the share of all class 4 first tests in each age band that recorded the item as an advisory, test years 2021 to 2025 pooled. A test can record more than one item, so the rows do not add up. Age is the test year minus the year the car was first used.
| Tyre advisory | Aged 3-5 | Aged 6-9 | Aged 10-14 | Aged 15 and over |
|---|---|---|---|---|
| Tread depth close to the 1.6mm limit | 12.9% | 15.7% | 18.1% | 16.9% |
| Tear in the tyre structure | 6.2% | 8.7% | 8.7% | 9.5% |
| Cut deep enough to reach the ply or cords | 1.7% | 1.4% | 1.2% | 0.9% |
| Bulge in the tyre structure | 0.7% | 0.7% | 0.6% | 0.5% |
Two patterns stand out. Tread notes rise through the first fourteen years and then fall back a little on the oldest cars. Tear notes rise steadily: about 1 in 10 tests on cars aged 15 and over (9.5%) carried one. Cuts and bulges go the other way, becoming slightly less common with age. The data records what the tester saw; it does not say why. Older cars tend to cover fewer miles a year, and their owners may replace tyres on a different rhythm, but none of that is in the dataset.
Why this matters now
Since the clocks went back on 25 October, most people's drive home is in the dark, and the roads are wet more evenings than not. Tread is what clears water from under the tyre. A tyre that passed the MOT in June with a tread advisory has had a summer of wear since, and the tester's note was telling you it did not have much to spare.
The legal line is set out in the Highway Code: cars must have at least 1.6 mm of tread across the central three-quarters of the tread and around the whole circumference. Tread below that is a dangerous defect at the MOT, and so is a lump, bulge or tear caused by the structure failing; a cut deep enough to reach the cords is a major defect. All three fail the test, and GOV.UK says driving with a dangerous problem can bring a fine of up to £2,500, a ban and 3 penalty points. The advisory is the step before any of that.
What to check this week
- Read the history first. Look up the car on the GOV.UK MOT history service and read the advisory lines from the last two tests. A tyre note that repeats is a tyre that was not changed.
- Measure the tread, not just the middle. The law covers the central three-quarters of the tread around the whole tyre. Uneven wear often shows on one edge only, so check the inner and outer shoulders too.
- Run a hand round the sidewall. Tears, bulges and lumps are the structure giving way and are a dangerous defect at the test. A bulge means the tyre needs replacing, not watching.
- Look into any cut. If you can see cord or fabric in the bottom of a cut without touching the tyre, the manual treats that as a fail.
- Set the pressures cold. The Highway Code says to check them weekly, before a journey, to the maker's figure for the load. Low pressure wears the shoulders and lengthens wet stopping distances.
What this does not mean
These are fleet figures: the share of millions of tests in each age band that carried a note. They say nothing about any single car. A ten-year-old car with four new tyres carries no tread advisory; a three-year-old car on its original tyres may. The shares also describe what testers recorded, and advisories involve the tester's judgement, so a note on one car's history is a prompt to look, not a verdict. The dataset has no tyre brand, no mileage per tyre and no record of why a tyre wore as it did, so this article does not say what causes the pattern, only that it exists.
Frequently asked questions
No. An advisory is recorded on a pass. GOV.UK describes advisories as problems to monitor or fix in the future. A tyre only fails when the tread is below the legal requirement, or the tyre has a cut reaching the cords, a lump, bulge or tear, or another defect listed in the manual.
At least 1.6 mm across the central three-quarters of the tread and around the entire circumference, according to the Highway Code. Tread below that is a dangerous defect at the MOT, and driving with a dangerous defect can bring a fine of up to £2,500, a ban and 3 penalty points.
Tread depth, by a wide margin. In tests carried out 2021 to 2025 it was recorded on 12.9% of first tests on cars aged 3 to 5, rising to 18.1% on cars aged 10 to 14. Tears in the tyre structure are second, at 6.2% to 9.5% depending on age.
More tread and tear notes, yes, though tread notes ease slightly on cars aged 15 and over. Cut and bulge notes are a little less common on older cars. The data records what was found at the test, not why, so it cannot say whether that is down to mileage, driving or how tyres are replaced.
Sources and method
Each figure is the number of class 4 first tests in an age band that recorded the named tyre item as an ADVISORY, divided by all first tests in that band, test years 2021 to 2025 pooled; age is test year minus first-used year. Bands hold 33,793,352 (aged 3-5), 50,103,915 (6-9), 44,980,002 (10-14) and 31,405,150 (15 and over) first tests. Items are per test, so a test with two tyre notes counts in two rows. A second tread wording in the dataset (tread pattern not visible where the minimum is 1.0mm) and the valve-stem items are omitted; nothing is added together. Advisories are the tester's judgement and the dataset records what was noted, not why.
- DVSA anonymised MOT results, class 4 first tests, 2021-2025
- GOV.UK: Check the MOT history of a vehicle
- GOV.UK: The Highway Code, Annex 6 vehicle maintenance
- GOV.UK: MOT inspection manual, section 5 (tyres)
- GOV.UK: After the MOT test
About these figures. Figures are computed by SortedCars from the DVSA anonymised MOT results dataset (class 4, first tests only, test years 2021-2025), published under the Open Government Licence v3.0. Pass rate = passes divided by first tests, with pass-after-rectification counted as a fail. No figure is shown for any group with fewer than 500 tests. Test class 4 only, first tests only; retests are excluded. Pass rates describe fleets, not individual machines: they reflect how cars were driven, maintained and used as well as how they were built, and beyond recorded mileage none of that is in the data. A well-kept example of a model with a weak average can still pass; a neglected example of a strong one can still fail. Alias spellings of a make are counted under one make name and all trims of a model under one model name, using SortedCars' grouping tables.
This article is general information drawn from published test records. It is not professional, mechanical or legal advice, and an MOT pass or a clean MOT history does not guarantee that a car is roadworthy today. If you are unsure about a car, have it inspected by a qualified mechanic. You can check any vehicle's MOT history free on the official GOV.UK MOT history service.
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