UN R172 Base text (01 series) · UNECE Regulation No. 172 (ECE R172) — Uniform provisions concerning the approval of retreaded tyres with regard to their snow performance and/or classification as traction tyre.
UN R172 — 01 series of amendments
Changes from 00 series of amendments (supplement 1)
- What changed
- A retreaded tyre can now also be classified as a “traction tyre” under new paragraph 6.2.2., by its number of traction elements and deformation potential (Pdef).
- Paragraphs 12.5. to 12.7. cover tyres of classes C2 and C3 classified as traction tyre that do not comply with paragraph 6.2.2. Their 01 series approvals need not be accepted if first issued after 1 September 2028, and in all cases as from 1 September 2032.
- New item (a) of paragraph 6.4. sets requirements for class C1 tyres to be classified as a 'professional off-road tyre'.
- Why
- To make sure retreaded and new tyres are consistent, the requirements for the traction tyre classification are aligned to UN Regulation No. 117.
- The transitional provisions make the switch from paragraph 6.2.1. to paragraph 6.2.2. follow the same rules and a timeline equivalent to UN Regulation No. 117.
- The C1 professional off-road tyre requirements were erroneously cancelled by Supplement 1 to the original version; the amendment confirms them for the 01 series.
Q1What changed44 changes
Traction tyre classification by traction elements (paras. 6.2. to 6.2.2.2.)
To be classified as a “traction tyre”, a retreaded tyre must now meet at least one of the conditions of paragraph 6.2.1. or 6.2.2. Before, it had to meet the conditions that are now in paragraph 6.2.1. New paragraph 6.2.2. requires a total number of traction elements (nTE) equal to or greater than a limit based on the deformation potential (Pdef). Pdef = Rvoid · dtr³; Rvoid is the void to fill ratio of the tread pattern, and dtr is the maximum of the tread depths in millimetres. The total nTE is ½ · (nTE,50 + nTE,70). Here, nTE,50 and nTE,70 count the traction elements separated by grooves/sipes with a depth of at least 50% and 70% of the maximum tread depth.
Minimum number of traction elements for class C2 and C3 tyres (para. 6.2.2.3.)
Paragraph 6.2.2.3. sets the minimum nTE for a traction tyre by tyre class and, for class C3 tyres, nominal rim diameter. For class C2 tyres: nTE ≥ −2/(25 mm3) · Pdef + 100. For class C3 tyres with nominal rim diameter code less than 20: nTE ≥ −1/(10 mm3) · Pdef + 200. For class C3 tyres with nominal rim diameter code equal to or greater than 20, if Pdef < 1400 mm3: nTE ≥ −17/(70 mm3) · Pdef + 400. For the same tyres, if Pdef ≥ 1400 mm3: nTE ≥ −1/(10 mm3) · Pdef + 200.
Professional off-road tyres of class C1 (para. 6.4.)
Paragraph 6.4. has a new item (a) for class C1 tyres to be classified as a 'professional off-road tyre'. For these tyres, it requires a tread depth ≥ 11 mm and a void-to-fill ratio ≥ 35 per cent. It also requires a speed category less than or equal to 160 km/h (speed category symbol Q). The former items (a) and (b) are now items (b) and (c).
Transitional provisions (paras. 12.1. to 12.7.)
Under new paragraph 12.1., no Contracting Party may refuse to grant or accept 01 series type approvals from its entry into force. Paragraph 12.2., on snow tests with SRTT19.5 and SRTT22.5, now says “shall not be obliged to grant” instead of “shall not grant”. Paragraph 12.4. now also covers the acceptance of existing type approvals of class C3 tyres, first issued before 1 September 2030. Paragraphs 12.5. to 12.7. cover tyres of classes C2 and C3 classified as traction tyre that do not comply with paragraph 6.2.2. For such 01 series approvals first issued after 1 September 2028, acceptance is not obliged as from 1 September 2028. Approvals first issued before 1 September 2028 must be accepted and extended until 31 August 2032; as from 1 September 2032, acceptance is not obliged.
Supplier of the tread (para. 2.2.), conformity of production (para. 8.) and Annex 1
In the definition of “Supplier of the tread used for retreading process”, the supplier is now responsible for the conformity of production “of the supplied tread”. Paragraph 8. now refers to Schedule 1 of the Agreement instead of Appendix 1. In Annex 1, “Extension No.:” is deleted after “Approval No.:”.
Q2Why it changed
- Proposed by
- Experts from the European Tyre and Rim Technical Organization (ETRTO)
- Working party
- GRBP, 83rd session (February 2026)
Reasons
To make sure retreaded and new tyres are consistent, the requirements for the traction tyre classification are aligned to UN Regulation No. 117.
Source
“To ensure consistency between retreaded tyres and new tyres, the requirements for the classification as “traction tyre” has been aligned to the ones given in the regulation No. 117.”
The transitional provisions make the switch from paragraph 6.2.1. to paragraph 6.2.2. follow the same rules and a timeline equivalent to UN Regulation No. 117. This aims to minimize the type approvals to be updated and the moulds to be modified. It also avoids retreaded and new tyres with the same tread pattern being classified differently as “traction tyre”.
Sources (5)
“Transitional provisions have been introduced to ensure that the switch from the requirements given in paragraph 6.2.1. to the ones given in the paragraph 6.2.2. will be required”
“with the same rules and with a timeline equivalent to the one implemented in UN Regulation No. 117.”
“Minimize the amount of type approvals pursuant the original version of regulation No. 172 to be then updated to the 01 series of amendments,”
“Minimize number of moulds to be modified due to the change in the series of amendments,”
“Avoid the situation where retreaded tyres would be classified as “traction tyre” whereas new tyres would not be classified as “traction tyre” and vice versa even if they have the same tread pattern.”
The requirements for the classification of special use tyres of class C1 as “professional off-road tyre” were erroneously cancelled by Supplement 1 to the original version. The amendment confirms these requirements also for the 01 series of amendments.
Sources (2)
“The requirements for the classification of special use tyres of class C1 as “professional off-road tyre” were erroneously cancelled by the amendments of the paragraph 6.4. made by Supplement 1 to the original version of UN Regulation No. 172.”
“The proposed amendment confirms such requirements also for the 01 series of amendments to Regulation No. 172”
The definition of the supplier of the tread is amended to clarify that it is responsible for the conformity of production of the supplied tread. The conformity of production procedures are in Schedule 1 of the 1958 Agreement, not in Appendix 1. Based on Revision 3 of the 1958 Agreement, the extension number is already included in the approval number. The transitional provisions on the SRTTs from Supplement 1 are amended to refer to the new series of amendments.
Sources (4)
“has been amended to clarify that he is responsible to assure the conformity of production of the supplied tread”
“However, the Conformity of production procedures are contained in Schedule 1 of that Agreement.”
“Based on Revision 3 of the 1958 Agreement, the extension number is already included in the approval number.”
“have been amended to refer to the new series of amendments.”
Proposer's reason (informal document GRBP-83-16-Rev.1)
Former paragraph 12.1., renumbered as 12.2., is amended because it is up to the Contracting Parties to decide whether to grant the type approvals. Former paragraph 12.3., renumbered as 12.4., now also considers the acceptance of existing type approvals in addition to their extension.
Submitted by Experts of ETRTO. Working party adoption: ECE/TRANS/WP.29/GRBP/83, para. 30.
Sources (2)
“It is proposed to amend the paragraph 12.1. (former), renumbered as 12.2., by considering that is up to the Contracting Parties deciding whether grant or not the type approvals.”
“Amendment to paragraph 12.3. (former), renumbered as 12.4., has been tuned by considering the acceptance of existing type approvals in addition to grant their extension.”
Document trail
- 2025-11ProposalECE/TRANS/WP.29/GRBP/2026/10Proposal by the experts from ETRTO
- —RevisedGRBP-83-15-Rev.1Shortened version to replace GRBP/2026/10
- —RevisedGRBP-83-16-Rev.1Expanded version to replace GRBP/2026/10
- —Working party adoptsECE/TRANS/WP.29/GRBP/83GRBP session report, para. 30
- 2026-04Sent to WP.29ECE/TRANS/WP.29/2026/100Text that GRBP sent to WP.29 and AC.1
- 2026-06-24WP.29 adoptsECE/TRANS/WP.29/1192Adopted at the 199th session (session report, para. 103)
- PendingIn forceDate not yet known
Q3Who is affected
Vehicle manufacturer
- No direct action for this role.
Component supplier
- For C2 and C3 traction tyres, calculate Pdef and nTE of your tread patterns to paragraphs 6.2.2.1. and 6.2.2.2.
- Check that C2 and C3 traction tyres meet the paragraph 6.2.2.3. limits for approvals first issued after 1 September 2028.
- For C1 professional off-road tyres, check tread depth ≥ 11 mm, void-to-fill ratio ≥ 35 per cent and speed category ≤ 160 km/h.
Technical service / Approval authority
- Be ready to check the counted traction elements and the Pdef calculation for C2 and C3 traction tyres (para. 6.2.2.).
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ⓘ This report gives advice only. It is not legal or type-approval advice.