UN R117 Base text (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 — 04 series of amendments
Changes from 03 series of amendments (supplement 1)
- What changed
- Paragraphs 6.2.1. to 6.2.3. add stage 2 wet grip limits for tyres in new state, and paragraph 6.3. adds stage 3 rolling resistance limits.
- New paragraph 3. of Annex 9 and new paragraphs 6.4.2. and 6.4.3. add wet grip in worn state for class C2 and C3 tyres.
- From 7 July 2024, Contracting Parties applying this Regulation need not accept type approvals to any preceding series first issued after 7 July 2024.
- Why
- Tighter rolling resistance limits can contribute to the further reduction of CO2 emissions and/or increase the range of battery electric vehicles.
- Tighter wet grip limits at new stage can help to reduce road accidents.
- For class C2 and C3 tyres, the Kworn factor reflects the wet grip drop of performance between tyres in new state and in worn state.
Q1What changed118 changes
Wet grip in new state: stage 1 and new stage 2 limits (paras. 6.2.1. to 6.2.3.)
Paragraphs 6.2.1. to 6.2.3. now give wet grip index (G) limits for tyres in new state at stage 1 and at a new stage 2. At stage 2, normal tyres of class C1 need G ≥ 1.2, instead of G ≥ 1.1 at stage 1. In classes C2 and C3, stage 2 raises the normal tyre limit (other than traction tyres) to G ≥ 1.10 and G ≥ 0.95. Stage 2 also gives G ≥ 1.1 for class C1 special use tyres, which have no limit at stage 1. For special use tyres, Annex 5 now gives test temperature ranges and, in tables 2 and 4, the coefficients a, b, c and d. Before, these cells said “not applicable” or “not defined”.
Rolling resistance: stage 2 and new stage 3 limits (para. 6.3.)
Paragraph 6.3. now has stage 2 rolling resistance coefficient (Cr) limits of 10.5, 9.0 and 6.5 N/kN for classes C1, C2 and C3. At stage 3, class C1 has 10.0 N/kN for load capacity index < 87, Run Flat Tyres, Extended Mobility Tyres and special use tyres. With load capacity index ≥ 87, tyres other than Run Flat Tyres or Extended Mobility Tyres have 9.0 N/kN. Tyres with a nominal aspect ratio ≤ 40 and suitable for speeds ≥ 300 km/h also have 10.0 N/kN. Class C2 tyres have 8.5 N/kN (traction tyres 9.0), and class C3 tyres 6.0 N/kN (tyres marked “C”, “CP” or “LT” 6.5). For snow tyres classified as tyres for use in severe snow conditions, the limits at both stages are increased by 1 N/kN.
Stage suffixes in approval marks (paras. 4.3.1., 5.2.2., 5.3.1.2. and 5.4.3., Annexes 1 and 2)
Under paragraph 5.2.2., W is now followed by 1 or 2, and R by 2 or 3, for compliance to the matching stage. Before, the paragraph said that S and R will be followed by the suffix “2” for compliance to stage 2. The suffix list in paragraph 5.4.3. now has W1 and W2 (wet adhesion level in new state at stages 1 and 2) and R3. The examples in paragraphs 4.3.1. and 5.3.1.2. now refer to the 04 series and use markings such as 04S2W2R3B. Annex 1, item 8., now lists wet adhesion in new state at (stage 1/stage 2) and rolling resistance at (stage 2/stage 3). The approval mark examples in Annex 2, Appendices 1 to 4, now refer to the 04 series.
Wet grip in worn state: class C1 table and new limits for classes C2 and C3 (paras. 6.4.1. to 6.4.3., Annex 9)
New paragraph 3. of Annex 9 evaluates GB in worn state of class C2 and C3 tyres from G in new state. GB is G times the performance drop factor Kworn: 0.87 for class C2 and 0.83 for class C3. New paragraphs 6.4.2. and 6.4.3. set GB limits, for example ≥ 0.82 (C2) and ≥ 0.66 (C3) for normal tyres other than traction tyres. For class C1 in paragraph 6.4.1., snow tyres now need GB ≥ 0.88 instead of ≥ 0.80, and special use tyres GB ≥ 0.80. Tyres with nominal aspect ratio ≤ 40, section width ≥ 235 mm and suitable for speeds ≥ 300 km/h now need GB ≥ 0.80. Before, a note decreased the limit by 0.08 for normal tyres with speed category ≥ 300 km/h and aspect ratio ≤ 40.
Traction tyres: new traction element rule (paras. 6.6. to 6.6.2.3. and 12.14. to 12.16.)
A tyre is now classified as a traction tyre if it meets at least one of the conditions of paragraph 6.6.1. or 6.6.2. Paragraph 6.6.1. keeps its tread pattern rule but no longer mentions an alternative physical test option at a later stage. New paragraph 6.6.2. requires a number of traction elements (nTE) at or above a limit based on the tread pattern deformation potential (Pdef). Paragraphs 6.6.2.1. to 6.6.2.3. give formulas for Pdef, nTE and the limits for class C2 and class C3 tyres. Approvals to the 04 series first issued after 7 July 2024 need not be accepted if a C2 or C3 traction tyre fails paragraph 6.6.2. Such approvals first issued before 7 July 2024 must be accepted until 31 August 2030.
Transitional provisions for the 04 series (paras. 12.1. to 12.13.)
From 7 July 2024, Contracting Parties applying this Regulation need not accept type approvals to any preceding series first issued after 7 July 2024. Until 6 July 2026, they must accept type approvals to the 02 or the 03 series first issued before 7 July 2024. From 7 July 2026, they need not accept type approvals to any preceding series. Paragraphs 12.3., 12.6. and 12.7. cover 04 series approvals not complying with stage 2 wet adhesion (new state) and stage 3 rolling resistance. Such approvals first issued after 7 July 2024 need not be accepted. Those first issued before must be accepted until 6 July 2026 for class C1 and until 31 August 2028 for classes C2 and C3.
Scope date (para. 1.1.7.) and class C1 special use tyres (para. 6.7.)
Paragraph 1.1.7. now refers to tyres designed only for vehicles registered for the first time before 1 October 2000, instead of 1 October 1990. A class C1 special use tyre now needs a tread depth ≥ 9 mm and a void to fill ratio ≥ 30 per cent. Before, these values were ≥ 11 mm and ≥ 35 per cent.
Q2Why it changed
- Proposed by
- Experts from the European Commission; Informal Working Group on Wet Grip Performance for Tyres in a Worn State; experts from the European Tyre and Rim Technical Organisation
- Working party
- GRBP, 76th session (September 2022)
Reasons
Tighter rolling resistance limits can contribute to the further reduction of CO2 emissions and/or increase the range of battery electric vehicles. According to studies, limits could be strengthened by up to 15 per cent (car tyres), 5 per cent (vans) and 8 per cent (trucks).
Sources (3)
“For rolling resistance, tighter limits can contribute to the further reduction of CO2 emissions and/or increase the range of battery electric vehicles.”
“According to studies for car tyres (84 per cent of tyre sales) limits could be strengthened by up to 15 per cent.”
“For vans (9 per cent of tyre sales) limits could be strengthened by up to 5 per cent and for trucks (7 per cent of tyre sales) limits could be strengthened by up to 8 per cent”
Tighter wet grip limits at new stage can help to reduce road accidents. This is important for the Vision Zero objective, as the average mass of vehicles tends to increase (battery electric vehicles, SUVs).
Sources (2)
“For wet grip, tighter limits at new stage can help reducing road accidents.”
“This is important to achieve the Vision Zero objective in a context where the average mass of vehicles tend to increase (battery electric vehicles, sport utility vehicles - SUVs).”
Class C1 tyres with aspect ratio ≤ 40, width ≥ 235 mm and speeds ≥ 300 km/h are usually designed for high performance cars. The hydroplaning effect is more pronounced on wider tyres than on normal tyres. All-terrain tyres of class C1 are also used in a more aggressive and abrasive environment than normal roads. So the C1 special use tyre category was revised, and special use tyres got worn-state prescriptions with a GB threshold of 0.80.
Sources (4)
“a section width equal to or higher than 235 mm and suitable for speeds equal to or greater than 300 km/h, usually designed to fit high performance cars”
“Hydroplaning effect is more pronounced on wider tyres than on normal tyres.”
“For all-terrain tyres of class C1 that are also used in a more aggressive and abrasive environment than normal roads and therefore require a specific tread design and compound with possible trade-offs on wet grip”
“For this reason, we introduce the prescriptions for wet grip in worn state also for special use tyres with a threshold for the wet grip index (GB) at 0.80.”
For C2 and C3 tyres, the concept of informal document GRBP-75-26-Rev.1 was transposed in a new paragraph 3 of Annex 9. The Kworn factor reflects the wet grip drop of performance between tyres in new state and in worn state. The GB limits are set based on the current wet grip limits in new state.
Sources (3)
“For C2 and C3 tyres, the concept presented in informal document GRBP-75-26-Rev.1 was transposed in a new paragraph 3 of Annex 9.”
“The concept of kworn factor was introduced to reflect the wet grip drop of performance between tyres in new state and in worn state.”
“The wet grip index GB limits are set based on the current wet grip limits in new state.”
The tyre industry investigated a test procedure to characterize traction tyres, but test reproducibility is very low, especially for soft soils. It was therefore decided to change from the current pure geometrical approach to a more mechanical approach.
Sources (2)
“the tyre industry investigated the possibility of a test procedure to characterize traction tyres. However, test reproducibility is very low especially for soft soils.”
“it was decided to change from the current pure geometrical approach to a more mechanical approach.”
Document trail
- 2022-06ProposalECE/TRANS/WP.29/GRBP/2022/12Proposal for the 04 series by the experts from the European Commission
- 2022-06ProposalECE/TRANS/WP.29/GRBP/2022/17Traction tyre proposal by the experts from ETRTO
- 2022-06ProposalECE/TRANS/WP.29/GRBP/2022/18Special use tyre proposal by the experts from ETRTO
- 2022-06ProposalECE/TRANS/WP.29/GRBP/2022/23Worn-state wet grip proposal by the IWG on Wet Grip Performance for Tyres in a Worn State
- —Working party adoptsECE/TRANS/WP.29/GRBP/74Session report, paras. 16, 22, 23 and 26
- 2022-12Sent to WP.29ECE/TRANS/WP.29/2023/8Text that GRBP sent to WP.29 and AC.1
- 2023-03WP.29 adoptsECE/TRANS/WP.29/1171Adopted at the 189th session (session report, para. 127)
- 2023-09-24In forceC.N.423.2023.TREATIES-XI.B.16.117UN depositary notification
Q3Who is affected
Vehicle manufacturer
- No direct action for this role.
Component supplier
- Check your tyres against the stage 2 wet grip limits of paragraphs 6.2.1. to 6.2.3.
- Check your tyres against the stage 3 rolling resistance limits of paragraph 6.3.
- For class C2 and C3 tyres, check GB = Kworn × G against the limits of paragraphs 6.4.2. and 6.4.3.
- Check whether your class C2 and C3 traction tyres meet the traction element rule of paragraph 6.6.2.
- For class C1 special use tyres, check the tread depth ≥ 9 mm and void to fill ratio ≥ 30 per cent.
Technical service / Approval authority
- For class C2 and C3 tyres in worn state, evaluate GB with Kworn as in Annex 9, paragraph 3.
- For Annex 5 tests of special use tyres, use the new temperature ranges and tables 2 and 4.
- Check class C1 results in worn state against the changed limits, for example GB ≥ 0.88 for snow tyres.
- When you check class C2 and C3 traction tyres, count traction elements as paragraph 6.6.2.2. describes.
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ⓘ This report gives advice only. It is not legal or type-approval advice.