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WGWT-03-01 rev1

3 rd session of the GRBP Informal Working Group

on Wet Grip on Worn Tyres (WGWT), September 10 th - 11 th (am) 2019




World Forum for Harmonization of Vehicle Regulations (WP.29)

Working Party on Noise and Tyres (GRBP)

Working Group on Wet Grip on Worn Tyres (WGWT), September 10th - 11th (am) 2019


Agenda of the 3 rd session of the Informal Working Group WGWT

September 10 th (9:00- 17:30) - 11 th 2019 (9.00-12.30) CET

At the Palais des Nations, Room XV, Geneva




Working Documents


Welcome and opening remarks



Introduction of participants and organizations



Adoption of the agenda and the minutes of previous meeting



Objective of the meeting






Action item WT-02-03

ETRTO will share the draft Excel workplan (Step 1) proposal
IWG members are invited to assess the draft proposal and to provide comments for September meeting.


Action item WT-02-04

ETRTO is requested to provide by next IWG meeting a detailed workplan including a time table.


Action item WT-02-05

IWG members that are candidate to perform tests or to provide are asked to inform the IWG by next meeting in September.


Action WT-01-11

France will provide more details on the test performed and presented

IWG experts will give their technical feedback and/or opposable/additional tests.

WT-02-02 rev2














Definition of worn tyre


  1. Tread depth


Action item WT01-01

IWG agreed to the requirements (to be included in the standard) on 4 points in the circumference:

-           Individual tread-depth: 2,0 +/- 0,4mm

-           Average tread-depth in principal groove: 2,0 +/- 0,3mm

-           Average tread-depth total measurements: 2,0 +/- 0,2 mm



Action item WT01-02

IWG experts will make the assessment on the buffing tolerance of their buffing equipment. Buffing target is 2 mm for this study (determination of α based on the proposal above).


  1. Wear profile
  1. Principal grooves

Flat profile (scenario 1 = worst case, to be further assess) and Offset (scenario 2) of the new profile.


Action item WT-02-01

IWG will reflect internally on the scenario 1 and 2 on what need to be considered or assessed in order to have an agreement during September session.


  1. Shoulder area

IWG agreed on the concept proposed in slide 9 of document WT-02-02-rev2


Action item WT-02-01

Industry is requested to finalize the shoulder wear profile definition. The proposal shall include a specific definition e.g. a k-factor table for the connection point”. Deadline: September


  1. Ageing


Action item WT-01-05

France will provide national data on the medium vehicle mileage per year.

OICA will try to have a more global data.


Action item WT-01-06

Tyre industry will investigate what could be the criteria to define the medium ageing of tyres (needs the outcome of action item WT-01-05)


Action item WT-01-07

EC will provide more information with already existing information: use, recommendation…


  1. Buffing Roughness definition


Action item WT-01-08

The buffing roughness is less significant but can be kept in the workplan.


WT-02-02 rev2



Tyre preparation (buffing method)


Action item WT-03-xx

ETRTO will present this draft procedure to prepare a worn tyre for September meeting.




Testing condition


Action item WT-03-xx

ETRTO will share the logic and principles of the new wet grip procedure (revised ISO test method) to the IWG.




Follow up of work 

-           Key elements / Planning

-           Measurement campaigns

WT-02-02 rev2


Any Other Business

-           Agenda for next meetings

-           Proposal from Russian Federation



Next meeting(s)


  •   Official sessions of IWG WGWT:

         Web conference?

         4 th Meeting: 27-28 (am) January GRBP – Geneva

         5 th Meeting: March 2020 – TBD

         6 th Meeting: May 2020 – TBD






All documents of this IWG WT are/will be available via the UNECE website: