How is grip on wet road surface established?

What you must do concretely

What is expected of you

Grip on wet road surface is determined using the test method from the tyre labelling regulation

Regulation (EU) 2020/740 sets out how grip on wet road surface (the "wet grip" class) is determined and classified in classes on the tyre label. For a company with 10 to 100 employees, this means in practice that the class shown on the label is not calculated or estimated by the company itself: it comes from the manufacturer or importer, based on the test method laid down in that regulation. Anyone who imports or trades in tyres takes over this class as supplied. No re-testing takes place, and no independent assessment is made based on experience with a particular brand or tread pattern.

The relationship with the product passport is established via the same underlying data

The product passport for tyres will build on data that largely already exists from labelling. The wet grip class is a good example of this: the same value that appears on the label will appear in the passport. How these two relate to each other precisely, and where they may diverge in form or level of detail, is described on the page about how the tyre label relates to the product passport. For practical purposes, it is important to know that measurement does not take place twice separately: one test result, two places where it appears.

The method for future measurements follows from Article 39 of the ESPR

For the broader product passports falling under the ESPR (Regulation (EU) 2024/1781), Article 39 determines that test, measurement and calculation methods are laid down by delegated act. For tyres, the measurement method for grip on wet road surface is already fixed via Regulation (EU) 2020/740, but for any new or additional requirements that come under the ESPR, the method is determined via that route. A company that compiles the passport does not need to interpret or choose that method itself: it is fixed at EU level. More on how this interplay of methods for different values works is on the page about the method by which the values for the passport are measured.

The supplied value is taken over, not recalculated

For companies that compile the passport on the basis of manufacturer data, this means that the wet grip class is a given that is taken over, checked for plausibility and placed in the correct place in the passport. No independent test report is drawn up, unless a company is itself a manufacturer or importer that has commissioned the original test. Anyone who doubts whether a stated class is realistic for a particular tyre type is well advised to check this with the party that supplied the data, rather than making an assessment themselves.

Where things go wrong in practice

A first situation that often occurs: an importer takes over a wet grip class from a supplier document that is no longer up-to-date, while the tyre is meanwhile being supplied in a new production run with adjusted rubber compound. The class on the label and in the passport is then no longer correct for the current tyre.

A second situation: with private label tyres (the same tyre, different brand), it is assumed that the wet grip class is automatically the same as that of the underlying model. This is usually the case, but is not always explicitly confirmed by the manufacturer, which leads to confusion as soon as someone asks for substantiation.

A third situation arises with seasonal tyres. Winter tyres and summer tyres are tested under different class classifications and with different expectations, and anyone who treats a winter tyre with the same documentation structure as a summer tyre runs the risk of putting incorrect or missing data in the passport. What differs in this regard is described on the page about seasonal tires and specifications.

A fourth situation: a wholesaler wants to adjust the wet grip class after the passport has already been published, because a new test round produced a different result. Without an established procedure for modifications, it becomes unclear which version of the passport is valid and from when.

A fifth situation applies to fleet managers who do not themselves import tyres, but do account for the chosen tyres to clients or financiers. They sometimes assume that every class on the label is traceable to a public test report, while the underlying test data from the manufacturer is not always freely accessible. What may and may not be shared in that regard is linked to the question of who may view which data from the product passport, as explained on the page about who may view which data from the product passport.

What you can record

• The original test document or the manufacturer's declaration of conformity in which the wet grip class is established, including date and tyre type
• An overview per tyre model of the test method used and the class that results from it, so that this does not have to be looked up repeatedly
• Agreements with suppliers on when a reassessment of the wet grip class is necessary, for example in case of changes to rubber composition or tread
• An established procedure for the event that a class is subsequently adjusted, including how that is implemented in an already published passport — the approach for this is described on the page about amending data after publication
• A brief internal explanation for staff who receive customer questions about the meaning of the wet grip class, so that not everyone interprets it differently
• An overview of which tyre models are private label and from which base model the test data have been taken, together with the manufacturer's supporting documentation