How Michelin Tests Its Tyres for Safety

For a tyre to be sold in the UK, it must have passed a safety test. So when brands talk about their own own testing, the question worth asking is what does the manufacturer test that isn't required by law?

For Michelin there's a clear answer. They are big proponenets of testing their tyres when they're worn. Not just when they're new.

In this piece we'll have a look at what that means, why it matters and what Michelin's claims don't tell you.

How does Michelin test its tyres?

Michelin designs and tests its tyres to keep performing to high levels in as the tread wears down. Not only when they're new.

They pushed for worn-tyre testing to become a legal requirement across Europe. This then became a requirement in July 2024.

Its worn-tyre results are measured by independent laboratories - at 2 mm of tread, not at the 1.6 mm UK legal limit.

Are all tyres safety tested before they're sold?

Yes. No tyre can be sold in the UK without passing type approval. That includes a minimum wet grip test.

There are two key pieces of regulatation that cover this:

• UN Regulation 30. Which covers how a tyre is built - size, load, speed rating.
• UN Regulation 117. That takes care of the performance: wet grip, rolling resistance and noise.

Since Brexit, the UK still uses these systems - with the Vehicle Certification Agency being the UK's approval authority.

The thing to understand is that type approval is a floor, not a score.

Passing it means a tyre isn't dangerous. However, it does not necessarily mean that it's going to deliver a high level of performance.

That's where the tyre label comes in to help consumers make sense of a lot of data.

The wet grip letter comes from the same test - it tells you how far above the minimum the tyre cleared, rather than simply that it did.

Why does Michelin test worn tyres?

Worn tyres. And they were big proponents of doing this before it was required. Michelin understood that a tyre doesn't perform the same way all its life.

Some things could be considered to actually get better as it wears. I.e. rolling resistance drops, and it gets quieter as tread wears down. However, you will find that wet braking goes the other way.

For years, the legal wet grip test only ever looked at a brand new tyre. Which meant a tyre could be approved on a performance it would not meet for much of it's lifespan. 

Michelin's argument, in its own words, is that tests shouldn't be limited to new tyres because wet braking is exactly the performance that fades.

They lobbied for stricter rules on this for years, and claimed that 99.5% of their own tyres would pass the ‘worn test’.

What is the worn tyre test and when did it become law?

Since July 2024, to gain approval a car tyre has to prove - through testing - that it still stops decisively in the wet - when it's close the legal tread depth limit.

To test for this, the tyre is machined down. Then it is tested from 80 to 20 kph on a wet surface with 1 mm of water. It gets a score based against the performance of a reference tyre.

As this is a fairly new piece of legislation, not every tyre on sale today has passed it. The rule applies to new tyre approvals, not to tyres made after July 2024. So a tyre manufactured today can still be on an approval granted years ago, before the worn test existed.

There's also a run-off period. Tyres approved under the older rules, and manufactured before 7 July 2026, can still be fitted to a vehicle until 6 January 2029.

How to check if a tyre was tested when worn

Look for the letter B in the approval mark on the sidewall. Every tyre that has passed a test carries an approval mark, and it uses a letter for each thing the tyre was tested on.

A mark reading 04S2W2R3B breaks down as:

• S for noise
• W for wet grip when new
• R for rolling resistance
• B for wet grip when worn.

You can find this in the small print near the bottom edge of the tyre. The rules say it must be on at least one sidewall, moulded into the rubber.

To pass, a normal car tyre has to score at least 0.88 on the worn wet grip index. Measured against a worn reference tyre.

Where does Michelin test its tyres?

Michelin test at their own facilities for the most part. These include:

• Ladoux, France. The main site, just outside Clermont-Ferrand with 450 hectares, 20 test tracks, 45 km of tarmac. It includes a 7.8 km high-speed circuit.
• Almería, Spain.4,500 hectares of dry-weather and high-temperature testing.
• Ivalo, Finland. An Arctic proving ground 300 km above the Arctic Circle for ice and snow work.

Michelin are heavily invested in their testing and research. With almost €1.2 billion a year in R&D and around 6,000 researchers spent by the French manufacturer.

Who tests Michelin tyres independently?

Independent laboratories are used to check results:

• Its worn-braking claims come from TÜV SÜD
• Its mileage claims from DEKRA

Both are published with the date, the tyre size and the car, so you can see exactly what was tested.

The headline example, from Michelin UK - a TÜV SÜD test in July 2024, 205/55 R16 on a VW Golf 8, braking from 80 to 20 kph in low-grip conditions.

To understand the table, it's important to remember that are index scores. Not braking distances. Each column is scored separately with the Primacy 5 set at 100 baseline.

So, the rows don’t tell us that the Primacy 4+ stops better worn than new. Every tyre's wet braking degrades as it wears. However, it shows that the gap between the two tyres closes over time.

When new, the Primacy 4+ is 8.6 points behind the Primacy 5. When it is worn, it's within a score of 0.8.

Michelin's claim is about how the newer tyre compares to the older one.

So interestingly, the older Primacy 4+ nearly catches up when worn, which shows that it held up well over time as well. Making for a strong generational improvement claim.

EV approved tyres: electric vehicle (EV) tyres are a category of car tyre that has been developed by several manufacturers to meet the specific requirements of an electric vehicle.

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What Michelin's testing claims don't tell you

Three things worth knowing before you take any of it at face value.

• Last mile is tested at 2 mm, not 1.6 mm. Michelin's own footnotes on their website define worn testing as buffed to 2 mm of tread. While noting the UK legal limit is 1.6 mm. That's the standard everyone uses for worn testing.
• Michelin paid for the tests. The labs are independent and reputable. The choice of size, car and comparison tyre made by Michelin. One size on a Golf and one on a Tesla is two data points, not a range.
• Independent group tests are the real cross-check. ADAC, Auto Bild, Auto Express and Tyre Reviews all run comparative programmes. Where every brand is tested side by side on the same day. 

Does any of this matter day to day?

Type approval and brand testing set what a tyre is capable of. What hurts people is tyres that have run well past the point where any of the safety features work.

Department for Transport figures, published in Reported Road Casualties Great Britain, show there is much to be done still in regards to safety and awareness.

Tyre-related deaths or seriously injured casualties rose from 169 in 2024 to 201 in 2025. With total casualties up 14% to 667.

On top of this, more than two million cars fail their MOT every year on tyre defects.

No testing or factory can help to fix that. The raising of awareness if key. This is why it's incredibly importanat that you do the following:

• Check your tread depth regularly. The UK legal minimum is 1.6 mm across the middle three-quarters of the tyre -  Regulation 27 of the Construction and Use Regulations and Annex 6 of the Highway Code. 
• Check your pressures monthly. Under-inflation sits alongside illegal and defective tyres in that casualty data. It's the cheapest safety fix there is.
• Read the wet grip letter when you buy. It's the one on the label that maps to stopping distance.