UN R117 Supplement 2 (04 series) · UNECE Regulation No. 117 (ECE R117) — Uniform provisions concerning the approval of tyres with regard to rolling sound emissions and/or to adhesion on wet surfaces and/or to rolling resistance.
UN R117 — Supplement 2 to the 04 series of amendments
Supplement 1 → 2
- What changed
- The Regulation now also applies to C1 tyres in new state with regard to their tyre abrasion, as defined in paragraph 1.3. Starting from 1 January 2027, the manufacturer must communicate the abrasion level during the approval of new types of class C1 tyres.
- Paragraph 2.18. adds the reference tyres “SRTT19.5 siped” and “SRTT22.5 siped”. The wet grip index of class C2 and C3 tyres and the snow grip index in paragraph 4.8.4. now include a factor f.
- As from 7 July 2025, Contracting Parties grant rolling sound type approvals only with the new temperature correction formula of Annex 3, paragraph 4.2.2.
- Why
- The aim is to introduce a methodology to measure tyre abrasion of C1 tyres. No limit is proposed, as a market assessment is required to define any performance level.
- The main goal of the new siped C3 reference tyres is to improve the reproducibility of the snow grip test method.
- The noise proposal aims to reduce variability; it says a dedicated 3PMSF temperature correction reduces the measurement uncertainty for class C1 tyres.
Q1What changed966 changes
Tyre abrasion information for class C1 tyres (paras. 1.1., 1.3., 2.21. and 5.7. to 5.10.)
Paragraph 1.1. now also covers C1 tyres in new state with regard to their tyre abrasion as defined in paragraph 1.3. New paragraph 1.3. excludes ice grip tyres and tyres having a nominal rim diameter code ≤ 13. For other class C1 tyres, approval must be supplemented with abrasion level information according to paragraphs 5.7 to 5.9. For new class C1 tyre types, the abrasion level may be determined upon request of the applicant until 31 December 2026 (paragraphs 5.7. and 5.8.). From 1 January 2027, the manufacturer must communicate the tyre type's abrasion level during the approval of new class C1 tyre types (paragraph 5.9.). Abrasion tests are not required for extensions of existing type approvals first granted before 1 January 2027 (paragraph 5.10.).
New Annex 10: procedure for determining the abrasion performance of tyres of class C1
New Annex 10 gives the procedure for determining the abrasion performance of tyres of class C1. The abrasion level of the candidate tyre is compared to the abrasion level of a standard reference test tyre. It is measured with test method (a), using a vehicle on public open roads, or test method (b), using an indoor drum. Both methods apply to C1 tyres in scope of this Regulation except ice grip tyres and tyres having a nominal rim diameter code ≤ 13. Annex 10 uses the reference tyres SRTT17S and SRTT17W. Its six appendices cover accelerations calculation, test report examples, the input of test cycle, test equipment tolerances and replacement of the sandpaper surface.
New siped reference tyres, ASTM updates and snow grip tests (paras. 2.18., 6.5.1. and 8.3.2.1., Annex 7)
Paragraph 2.18. now also defines “SRTT19.5 siped” (ASTM F3678 – 23, size 245/70R19.5) and “SRTT22.5 siped” (ASTM F3677 – 23, size 315/70R22.5). For SRTT14, SRTT16, SRTT16C, SRTT19.5 and SRTT22.5, the paragraph now refers to newer editions of the ASTM standards. In the table of paragraph 6.5.1., the reference tyres “SRTT19.5, SRTT22.5” now also include “SRTT19.5 siped, SRTT22.5 siped”. The paragraph 4.8.4. snow grip index now has factor f: 1.000 for SRTT19.5 and SRTT22.5, 1.570 for SRTT19.5 siped, 1.680 for SRTT22.5 siped. In paragraph 4.9.2., f also applies to SG1, and the test report in Annex 7, Appendix 3, Part 5 has a new row for f. On the tyre manufacturer's request, class C3 verification tests under paragraph 6.5.1. may use the same reference tyre as the original approval (new paragraph 8.3.2.1.).
Wet grip tests of class C2 and C3 tyres (Annex 5, Part (B))
Under paragraph 1.1.1., the class of the candidate tyre and the method (trailer or vehicle) now decide how the wetted track friction is established. A new table gives the friction range for each tyre class and reference tyre, for the trailer method (μpeak) and the vehicle method (BFC). New paragraph 1.1.1.2. adds a method using SRTT16C, SRTT19.5, SRTT22.5, SRTT19.5 siped and SRTT22.5 siped, with no temperature correction. In paragraphs 2.1.2.13. and 2.2.2.7.2., new item (b) requires the initial and final reference tyre averages of a test cycle within the paragraph 1.1.1. range. Paragraph 1.4. now lists SRTT19.5, SRTT22.5, SRTT19.5 siped or SRTT22.5 siped for class C3 tyres, instead of a “Narrow family” and a “Wide family”. The wet grip index formulas in paragraphs 2.1.2.14. and 2.2.2.7.5. now include a factor f: 1.02 for SRTT19.5 siped and SRTT22.5 siped, otherwise 1.
Rolling sound temperature correction and Annex 4 (paras. 8.3.4. and 12.18. to 12.20., Annex 3, paras. 4.2.1. and 4.2.2.)
New paragraph 4.2.2. gives a new temperature correction formula for rolling sound levels of class C1 and class C2 tyres (ϑref = 20 °C). Paragraph 4.2.1. applies until 6 July 2025 (paragraph 12.18.), and paragraph 4.2.2. from 7 July 2025 (paragraph 12.19.). Under paragraph 12.20., Contracting Parties continue to grant extensions of approvals first granted before 7 July 2025 with paragraph 4.2.1. A new test on a different representative tyre size for an extension after 6 July 2025 must use paragraph 4.2.2. New paragraph 8.3.4.: on the tyre manufacturer's request, verification tests for paragraph 6.1. approvals may use the same temperature correction formula as the original approval. Annex 4 “Specifications for the test site” is now “Reserved”, and the test site text no longer refers to Annex 4.
Transitional provisions for the C3 reference tyres (paras. 12.21. to 12.26.)
Under paragraphs 12.21. and 12.22., as from 1 September 2028, Contracting Parties are not obliged to accept certain approvals first issued after 31 August 2028. These are approvals to this supplement with Annex 5 wet adhesion tests in new state or Annex 7 snow performance tests using SRTT19.5 or SRTT22.5. Under paragraphs 12.23. and 12.24., extensions of class C3 approvals first granted before 1 September 2028 with SRTT19.5 or SRTT22.5 continue to be granted. Supplement 2 approvals first issued before 1 September 2028 are accepted until 31 August 2028 if listed tyres establish wet adhesion track characteristics (paragraph 12.25.). Paragraph 12.26. names the reference tyres from 1 September 2028: SRTT16C (class C2), SRTT19.5 siped or SRTT22.5 siped (class C3). Contracting Parties are not obliged to accept approvals to this supplement if the track characteristics are not established with these tyres.
Snow tyre definition, title of paragraph 6. and editorial updates (paras. 2.13. and 6.)
In the “Snow tyre” definition of paragraph 2.13., “structure” is now “construction”, and “in snow conditions” is now “in mud and/or snow conditions”. The tyre's ability to “initiate or maintain” vehicle motion is now its ability to “initiate and control” vehicle motion. The title of paragraph 6. is now “Requirements” instead of “Specifications”. Paragraph 8.3.2., Annex 7, paragraph 2. and Annex 8, paragraph 2.4.5.1.2. now refer to paragraph 6.5. or 6.5.2. instead of 6.4. or 6.4.2. References to ISO standards are updated, and the unit is now written “newtons” instead of “newton”. Footnote 1 now refers to the Consolidated Resolution on the Construction of Vehicles (R.E.3) without a document number or web address.
Q2Why it changed
- Proposed by
- Informal Working Group on Measurement Uncertainties (IWG MU); experts from the European Tyre and Rim Technical Organization (ETRTO); Task Force on Tyres Abrasion
- Working party
- GRBP, 78th session (August–September 2023) and 79th session (February 2024)
Reasons
The Task Force on Tyre Abrasion proposes a new methodology to measure tyre abrasion of C1 tyres. Two methods are proposed: a vehicle test method on public open roads and an indoor drum test method. No limit for tyre abrasion is proposed, as a market assessment is required to define any performance level. The approach has two steps: first the test methods for C1 tyres, then, at a later stage, limits to comply with. Ice grip tyres are expected to have different use and behaviour, so the proposal does not consider them.
Sources (5)
“TFTA is proposing to introduce a new methodology to measure tyre abrasion of C1 tyres in UN Regulation No. 117.”
“two methods are proposed: a vehicle test method on public open roads and an indoor drum test method.”
“No limit for tyre abrasion is proposed in the current text as a market assessment is required to define any performance level.”
“the introduction of the tyre abrasion in the Regulation is a two steps approach: implementation of the test methods for C1 tyres to introduce, at a later stage, limits to comply with”
“ice grip tyres. The latter are expected to have different use and behaviour and thus are not considered in the current proposal.”
The Informal Working Group on Measurement Uncertainties proposed measures to reduce variability. The proposal states that a dedicated three-mountain-peak snowflake (3PMSF) temperature correction reduces the measurement uncertainty for class C1 tyres. The change from a bi-linear to a logarithmic function is in line with the temperature behaviour of rubber. For class C2 3PMSF tyres and class C3 tyres, no necessity for a temperature correction formula was observed, due to their low temperature sensitivity. As conformity of production can occur much later, manufacturers may use the old or new temperature correction at that time. The proposal gives a 6-month transitional provision because of the accreditation of technical services according to ISO 17025.
Sources (6)
“prepared by the experts of the Informal Working Group on Measurement Uncertainties (IWG MU) in order to introduce measures to reduce variability.”
“the proposed introduction of a dedicated three-mountain-peak snowflake (3PMSF) temperature correction reduces the measurement uncertainty for class C1 tyres.”
“The proposed update from a bi-linear towards a logarithmic function for the temperature correction is in line with the temperature behaviour of rubber”
“For class C2 3PMSF tyres, and similarly to C3 tyres, no necessity to introduce a temperature correction formula was observed due to their low temperature sensitivity.”
“this proposal will give each manufacturer the opportunity to use the old or new temperature correction, depending on the acquisition and elaboration system available at the time of COP”
“Considering the accreditation of technical services according to standard ISO 17025, a 6-month transitional provision”
The main goal is to improve the reproducibility of the snow grip test method. To do this, the proposal replaces the current C3 reference tyres SRTT19.5 and SRTT22.5 with new siped versions. For the wet grip test, SRTT19.5 and SRTT22.5 were not interchangeable, which caused uncertainty in testing and logistic difficulties. The proposal validates the C2 and C3 track and each test session with the same method and reference tyres as the test. The transitional provisions let technical services adapt the test tracks, if needed, and avoid premature disposal of the current SRTT19.5 and SRTT22.5.
Sources (6)
“the main goal of this supplement is to improve the reproducibility of the snow grip test method by replacing the current reference tyres C3 SRTTs 19.5 and 22.5 with the new reference tyres C3 SRTTs 19.5 and 22.5 siped.”
“SRTTs 19.5 and 22.5 are currently not interchangeable for the wet grip index test, being their choice linked to the section width of the candidate tyre.”
“This provision generates uncertainty in testing and logistic difficulties”
“it is proposed to validate both the C2 and C3 track surface and the tests results of each test session using the same method and the same reference tyres used in the evaluation program itself.”
“Transitional provisions are introduced to ensure that technical services may adapt, if needed, the test tracks to the new requirements”
“to assure a smooth transition to the new SRTTs 19.5 and 22.5 siped without premature disposal of current SRTTs 19.5 and 22.5.”
The title of paragraph 6 is changed to “Requirements”, more in line with its content and with UN Regulations No. 30, 75 and 106. The reference to R.E.3 is simplified to avoid the need of continuous update with new revisions. The snow tyre definition is aligned to the one in UN Regulations No. 54 and 75. The references to ISO and ASTM standards are updated.
Sources (5)
“The title of paragraph 6 is changed to Requirements, more in line with its content and with UN Regulations No. 30, 75 and 106.”
“the reference to the Consolidated Resolution on the Construction of Vehicles (R.E.3) is simplified to avoid the need of continuous update with new revisions.”
“The snow tyre definition is now aligned to the one in UN Regulations No. 54 and 75.”
“The reference to ISO standards is updated in many paragraphs.”
“The updated reference to ASTM standards is provided in paragraph 2.18.”
Proposer's reason (informal document GRBP-79-21)
Paragraph 8.3.2.1. considers the availability of the C3 SRTTs when the conformity of production occurs. It gives each manufacturer the opportunity to use the same reference tyre as for the type approval.
Submitted by Experts of the European Tyre and Rim Technical Organisation. Working party adoption: ECE/TRANS/WP.29/GRBP/77, para. 22.
Sources (2)
“Paragraph 8.3.2.1. is introduced to consider the availability of the C3 SRTTs when the conformity of production (COP) occurs.”
“This proposal will give each manufacturer the opportunity to use the same reference tyre used for the type approval.”
Document trail
- 2023-06ProposalECE/TRANS/WP.29/GRBP/2023/19Proposal by the Informal Working Group on Measurement Uncertainties
- —RevisedGRBP-78-05IWG MU text that GRBP adopted
- —Working party adoptsECE/TRANS/WP.29/GRBP/76GRBP session report, para. 23
- 2023-11ProposalECE/TRANS/WP.29/GRBP/2024/4ETRTO proposal with editorial corrections
- 2023-11ProposalECE/TRANS/WP.29/GRBP/2024/6ETRTO proposal for the new C3 reference test tyres
- 2023-11ProposalECE/TRANS/WP.29/GRBP/2024/10Proposal by the Task Force on Tyres Abrasion
- —Amended in sessionGRBP-79-21ETRTO proposal to replace ECE/TRANS/WP.29/GRBP/2024/6
- —Amended in sessionGRBP-79-12-Rev.2Amendments to ECE/TRANS/WP.29/GRBP/2024/10
- —Working party adoptsECE/TRANS/WP.29/GRBP/77GRBP session report, paras. 22 and 29
- 2024-04Sent to WP.29ECE/TRANS/WP.29/2024/65Text that GRBP sent to WP.29 and AC.1
- 2024-06WP.29 adoptsECE/TRANS/WP.29/1179Adopted at the 193rd session (session report, para. 162)
- 2025-01-10In forceC.N.95.2025.TREATIES-XI.B.16.117UN depositary notification
Q3Who is affected
Vehicle manufacturer
- No direct action for this role.
Component supplier
- From 1 January 2027, communicate the Annex 10 abrasion level for new class C1 tyre types covered by paragraph 1.3.
- Until 31 December 2026, decide on requesting Annex 10 abrasion levels for new class C1 types (paragraphs 5.7. and 5.8.).
- For approvals first issued after 31 August 2028, plan Annex 5 and Annex 7 tests without SRTT19.5 or SRTT22.5.
- Check C1 and C2 rolling sound levels with the Annex 3, paragraph 4.2.2. correction for approvals from 7 July 2025.
- Under paragraph 8.3.2.1., decide whether to request the original reference tyre for paragraph 6.5.1. verification tests of class C3 tyres.
Technical service / Approval authority
- Be ready to run Annex 10 abrasion tests of class C1 tyres with test method (a) or test method (b).
- Check C2 and C3 wetted track friction against the range for the SRTT and method in the paragraph 1.1.1. table.
- For class C3 tyres tested against SRTT19.5 siped or SRTT22.5 siped, use f = 1.02 in the wet grip index.
- For snow grip tests against SRTT19.5 siped or SRTT22.5 siped, use f = 1.570 or f = 1.680 respectively.
- For type approvals from 7 July 2025, apply the Annex 3, paragraph 4.2.2. temperature correction to C1 and C2 tyres.
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ⓘ This report gives advice only. It is not legal or type-approval advice.