Proposal for acceleration calculation based on GNSS data to amend document GRBP/2025/27.

Guidance document on the Procedure for Demonstrating Equivalence of Vehicle Test and Indoor Drum Test Facilities for Tyre Abrasion and Determining the Transfer Function for Indoor Drum Test Facilities

Procedure for Demonstrating Equivalence of Vehicle Test and Indoor Drum Test Facilities for Tyre Abrasion and Determining the Transfer Function for Indoor Drum Test Facilities

The document establishes procedures for demonstrating equivalence between vehicle circuit and indoor drum test facilities. It defines requirements for selecting exercise tyres and participating facilities, establishing baseline values from multiple facilities, and comparing facility results against baselines. For indoor drum facilities, transfer functions mathematically relate drum results to vehicle results, either as generic (fixed coefficient) or specific (facility-determined coefficient). Facilities must meet statistical criteria including result deviation limits and root mean square deviation thresholds to demonstrate equivalence.

The 47th session of the Task Force on Tyre Abrasion convened on 2 April 2026. The review committee prepared final consolidation of a new UN Regulation on Tyre Abrasion for WP.29. TFTA reviewed the workplan including data assessment, tyre batch use, and equivalence assessment governance. For C2, ETRTO presented findings on the vehicle test method at 10,000 km, while JASIC reported on indoor drum test development. Discussion on C3 Heavy-Duty Vehicle tyre applications was deferred. The next session is scheduled for 11 May 2026.

ETRTO proposed three ways to estimate service life (TA-36-04): tread depth measurements, initial tread depth and abrasion index, and tread mass. JRC presented a service life index (TA-32-04) based on tread depth measurements and conducted a preliminary assessment of the second concept. Service life is estimated by linear extrapolation to 1.6 mm from tread measurements at test start and end. The Service life index is calculated as the ratio of candidate to reference tyre service life. Next steps include confirming the equation for service life via tyre characteristics and clarifying which tyre characteristics are needed.

The agenda includes discussion of status of the work plan 2026 including the ITTAC proposal on tyre abrasion Convoy Method -Dual-Normalisation Framework (TA-45-08/Rev.1) and UTAC Tyre abrasion timeline Gantt (TA-46-03/Rev.1), development of the C1 tyre mileage potential metric and tread depth measurement prescription, and test method development status under C2 and C3.

Existing C1 tyre-abrasion test methods cannot be directly applied to C3 tyres because vehicles equipped with C3 tyres are used differently. Japan is developing a vehicle test method using WHVC mode and plans to develop a drum test method based on test conditions and results. Test conditions will convert vehicle driving conditions representing the world into indoor drum test settings. C2 test method uses driving mode based on WLTP with fixed test load details, with verification tests using reference tyres. For C3, driving modes and test conditions are under preliminary investigation, with verification tests to be planned.

DEKRA Test Center examined whether vehicles fitted with SRTT impact tyre abrasion rates. Tests DEKRA #104 and DEKRA #41 compared SRTT Summer as candidate against SRTT Winter as reference, with abrasion indices of 1.18 and 1.19 respectively, showing no vehicle impact. Tests DEKRA 8 and DEKRA 9 showed abrasion rates of 45.1 mg/km/T and 45.0 mg/km/T respectively with no difference despite different vehicles. A 2024 convoy test with two Golf vehicles fitted with identical SRTT Summer showed a difference of 1 gram cumulated weight loss after 7,962 km (0.07 mg/km/T). DEKRA concludes the impact on abrasion level of the reference vehicle using SRTT is low or very low.

The document presents a European heavy-duty vehicle and tyre market overview and C3 test method development status. The C3 tyre market is complex and diversified, with applications including long haul, regional, on/off road, winter, and urban use. A test concept has been developed focusing on road usage with 22.5" tyres, using convoys of up to four vehicles with defined acceleration standards, road distribution of 60% motorway and 40% regional roads, and tests per axle comparing candidate tyres to reference tyres. Current activities include assessment of reference tyres strategy, temperature sensitivity evaluation, and confirmation of test parameters for heavy trucks in N₃/O₃ configuration, with tests reaching 30,000 to 45,000 kilometres.

TA-48-02 updates TA-47-02. C2 tyre abrasion rate index vehicle method uses a convoy of up to 4 vehicles with single tyres, GVW up to 3.5T, FWD, loaded 60%–74% of tyre nominal load with 50/50 front/rear distribution. Test distance is 10000 km at 80% nominal pressure. Reference tyres use 2 sets of test runs with C2 candidate SRTT and existing C1 SRTTs. 2025 testing in 235/65R16C and 205/65R16C sizes showed C2 tyres sensitivity to temperature similar to C1 tyres. 2026 plan repeats and extends 2025 testing to confirm reference tyres strategy, assess temperature sensitivity and pressure impact, and define validation plan.

The SWG on data assessment defines its scope as organisational matters for the Confirmation plan 2026, data anonymisation, governance and data storage to be defined. Its mandate includes preparation of tyre selection for the Confirmation plan, informing and collecting information from candidate test facilities, organizing tyre availability and shipments, and preparing data for TAPP data assessment including data collection and compilation.

The agenda includes status updates on the Convoy Method Dual-Normalisation Framework, tyre abrasion timeline, and test method development for mileage potential metric, tread depth measurement, and C3 tyre abrasion. Action items include ETRTO uploading acceleration calculation examples to the TFTA wiki, TFTA reviewing the Gantt chart, and the SWG on data assessment redefining its scope by the 49th session.

• ETRTO to check feasibility to upload acceleration calculation examples on TFTA wiki,
• SWG on data assessment to define scope and mandate by 49th session,
• ITTAC proposal (TA-45-8v1) on Convoy Method Dual-Normalisation Framework deferred to next session,
• UTAC Gantt timeline reviewed; ETRTO regulatory experts reviewed proposal; technical experts review pending,
• Tyres Europe stated EU Tire Industry funded over 3m for C1 activities and will provide over 1m additional financing for C2 and C3 work; requested TFTA co-financing,
• EC will escalate request; JRC will participate with 2 convoys for C2 in 2026 and C3 in 2027,
• SWG on data assessment to define scope, mandate, and leader for next session,
• DEKRA presentation on vehicle impact with SRTT; vehicle effect neutralized through tyre rotation for correlation purposes,
• JRC service life update presented; analysis planned for end of 2026,
• ETRTO C2 test method development restarted May 2026; temperature impact observed for winter SRTT requiring 2026 workplan verification,
• GRBP Working Document delivery for C2 test method postponed to February 2027,
• ETRTO and JASIC C3 presentations deferred for comments next session.

The document presents reflections on equivalence criteria for C2 tyres under Annex 4. C1 and C2 protocols are expected to remain very similar, with most changes having no impact on ALI and facility correlation. Key differences include tyre load and inflation pressure specifications. The main hypothesis states that if final C2 methods remain closely aligned to C1 methods, the existing equivalence framework for C1 could be maintained and extended to C2 testing, with already equivalent facilities receiving automatic equivalence or minor validation, and new facilities requiring amendment of Annex 4 to accept a mix of C1 and C2 tyres for demonstration of equivalence.

The Tyre Abrasion Task Force has completed tyre selection for the Confirmation plan 2026 and informed candidate test facilities. Tyre availability and shipments remain ongoing. Data collection and compilation for data assessment awaits test commencement. The SWG on Data Assessment has agreed to transfer discussions regarding exclusion criterion for high variability tyres and acceleration corrections to TAPP upon its resumption of meetings.

Draft minutes of the 49th session of the Task Force on Tyre Abrasion (TFTA), held June 3rd, 2026 (9:00–12:00 CET). Previous meeting minutes were approved. Action item TA-48-1: ETRTO to check feasibility to upload acceleration calculation examples on TFTA wiki. ETRTO confirmed feasibility assessment completed; example files could be moved to TFTA wiki with a disclaimer that TFTA is not responsible for example content. Action item TA-49-1: ETRTO will prepare disclaimer to be reviewed and validated by TFTA during 50th session. Agenda adopted. ETRTO presented comments on updated Gantt prepared by UTAC per document TA-49-03. TFTA agreed to evaluate data analysis per tyre segment when data available. JASIC requested more time to review and provide feedback next session. ETRTO and JATMA tyre manufacturers ready to make selected tyres available; first orders and deliveries started last week of May. Training session on best practices organized 2nd half of June. Action item TA-48-2: SWG on data assessment to redefine scope and mandate. SWG leader presented amendment proposal per document TA-49-02. TFTA agreed with SWG scope and mandate per TA-49-02/Rev.1. ETRTO stated mileage potential work should address all TFTA members and tyre manufacturers associations at UN level. JRC studying tread depth divided by abrasion index approach. Topic readdressed next TFTA. ETRTO noted test campaign running; final results expected Q4 2026 including 2nd set Normal and 3PMSF temperature behavior tests and pressure impact test. Action item TA-49-2: EC and JRC will reflect by next TFTA session how annex 4 would be impacted considering C2 tyres. TFTA co-chair suggested extraordinary brainstorming session end September/beginning October 2026 for C3 tyre abrasion test method development. Next meetings: 50th session July 6 (9:00–12:00 CET); 51st session August 25 (9:00–12:00 CET).

Draft agenda of the 50th session of the Task Force on Tyre Abrasion, scheduled for July 6th, 2026 (9:00-12:00 CET). The session will address the status of the 2026 workplan, organizational matters, workplan updates, best practice meetings with test facilities, ITTAC proposal on tyre abrasion Convoy Method Dual-Normalisation Framework, UTAC tyre abrasion timeline, TFTA activities financing, development of the mileage potential metric, test method development status for C1, C2, and C3 tyres, preparation of supplement 1 to UN Regulation No. 186, and improvements to test methods.