Project: Development of a Test Procedure for Measurement of Vehicle Tyre Grip Phases 1 and 1A

Reference: S340D/VD

Last update: 02/12/2003 10:00:12


This project will contribute to the development of a test procedure for measuring the wet grip of both car and truck tyres, which can be readily and economically applied by a type approval authority or other test agency.

In considering the economics, the project will examine the option of using a specially developed trailer for regulatory testing of the wet grip of tyres and will compare this against the possible variability of results achieved using a standard vehicle.

The prime objective of this research project is to provide information that will assist in the development of a test procedure to allow for the regulatory control of tyre grip, that will ensure at the very least, current levels of grip are maintained.


Tyre design is a compromise between many performance factors. Traditionally the manufacturer has had the freedom to establish the balance between these factors without any regulatory control. However, with the recent adoption of the EU Directive 2001/43/EC to introduce regulatory control of tyre to road noise emissions, there is concern that this could lead to an imbalance in the design compromise. The major concern relates to tyre grip, particularly in wet conditions, which may be adversely affected and up to the present time there has not been any regulatory control of this aspect. However, the Directive contains a commitment for the European Union Commission to adopt provisions for the regulatory control of tyre grip in order to maintain at least the current levels of adhesion in the future.

The Directive also indicates that there may be future regulatory control of other aspects of tyre performance, for example, rolling resistance, and the development of tyre grip test procedures is important to preserve what is the major function of the tyre, to provide grip for braking and cornering.

This part of the project funds UK involvement in collaborative research with TUV of Germany and the Netherlands to conduct comparative testing of the wet grip of car tyres at a number of European test sites. This will contribute to the development of a test procedure that can be applied by type approval authorities.


TUV Automative
24 Bennetts Hill, Birmingham, B2 5QP
(44) 0121 634 8000

Contract details

Cost to the Department: £53,709.00

Actual start date: 01 September 2000

Actual completion date: 31 May 2003


UBA-FB 201 54 112. Determination of the State-of-the-Art Concerning Rolling Noise, Rolling Resistance and Safety Properties of Modern Passenger Car Tyres - Final Report
Author: TUV Atomotive GmbH
Publication date: 15/12/2002
Source: Contact

UBA-FB 201 54 112. Wet Braking Performance of Selected Passenger Car Tyres - Addendum Report
Author: TUV Automotive GmbH
Publication date: 01/05/2003
Source: Contact

Summary of results

  1. Summarising the outcome of the research, the following conclusions can be drawn:

    The existing wide spread in wet braking performance among the same types of tyres definitely conflicts with the efforts to increase the safety of road users. With the purchaser / driver being unable to determine whether he has a product from the top or the low end of the range regarding wet grip ability, (the tyre make and purchase price are not necessarily a reliable criterion), a reasonable limit for the minimum performance is required.

    Tests with more than 400 market available passenger car tyres have shown a considerable spread of wet braking ability among tyres of the same type. To a certain extent, this divergence has to be regarded as tolerable, particularly in view of the individual development preferences of the manufacturers and in order to ensure sufficient scope for the optimisation of other tyre properties such as comfort, rolling noise, rolling resistance endurance, etc. However, performance differences of up to 30% have appeared in some tyre groups, which cannot be tolerated, particularly with regard to the consequences for traffic and driving safety. Under real road conditions, with the achieved absolute decelerations, this would result in a braking distance from 80 km/h to stop, on a wet road, of up to 10 meters longer for a vehicle equipped with the badly performing tyres. It would still be travelling at a speed of almost 40 km/h when a vehicle with the best tyre of the same size and range of use would have managed to come to a standstill. Yet, this very bad tyre performs over 10% better than the Standard Reference Test Tyre (SRTT) when being tested in the suggested method.