UN R30 Supplement 27 (02 series) · UNECE Regulation No. 30 (ECE R30) — Uniform provisions concerning the approval of pneumatic tyres for motor vehicles and their trailers.
UN R30 — Supplement 27 to the 02 series of amendments
Supplement 26 → 27
- What changed
- On run flat or self-supporting tyres suitable for speeds above 240 km/h but not above 300 km/h, “ZRF” may replace “RF”. Above 300 km/h, “ZRF” must replace “RF”.
- The “principal grooves” definition no longer refers to tread-wear indicators. The central zone is now defined as the area of 75 per cent of the tread width, measured symmetrically from the centre line.
- New paragraph 2.39. defines “tread depth” as the depth of the principal grooves.
- Why
- The proposal clarifies the structure indication “ZRF” in the size designation of run flat or self-supporting tyres above 240 km/h.
- The proposal changes the principal grooves definition to remove the circular reference between this definition and the position of tread wear indicators.
- The requirements for special use and professional off-road tyres use the new “tread depth” definition.
Q1What changed22 changes
“ZRF” marking on run flat or self-supporting tyres above 240 km/h (para. 2.25.3.4.1.)
New paragraph 2.25.3.4.1. covers run flat or self-supporting tyres for speeds above 240 km/h. Up to 300 km/h (speed-category symbol “W” or “Y”), the inscription “ZRF” may replace the letters “RF” before the nominal rim diameter. Above 300 km/h, “ZRF” must replace “RF”. The former paragraphs 2.25.3.2. to 2.25.3.5. have new numbers. Their text does not change.
Groove and tread depth definitions (paras. 2.19., 2.19.1., 2.19.2. and 2.39.)
Paragraph 2.19. now defines “tread groove” as the space between two adjacent ribs and/or blocks in the tread pattern. The old term was “tread pattern groove”, and the old text said “ribs or blocks”. “Principal grooves” are now the wide tread grooves in the central zone: 75 per cent of the tread width, measured symmetrically from the centre line. Before, they were the wide circumferential grooves in the central zone, with the tread-wear indicators in their base. The principal and secondary groove definitions move from paragraphs 2.39.1. and 2.39.2. to 2.19.1. and 2.19.2. The former text “Tread pattern grooves” of paragraph 2.39. is deleted, and new paragraph 2.39. defines “tread depth” as the depth of the principal grooves.
Nominal rim diameter (paras. 2.25.4., 2.26. and 2.26.1.)
Paragraph 2.26. now defines the nominal rim diameter as a conventional number that denotes the diameter of the rim. The number is a code (below 100) or a value in millimetres (above 100), but not both. Before, paragraph 2.25.4. gave the codes and millimetres explanation, and paragraph 2.26. defined it as “the diameter of the rim on which a tyre is designed to be mounted”. Paragraph 2.25.4. now only says “the nominal rim diameter”. In paragraph 2.26.1., the millimetre values are now the values of the “d” symbol when the nominal rim diameter is expressed by code. Before, they were the values of the nominal rim diameters for code-designated rims.
Section width and overall width specifications (paras. 6.1.1.1. and 6.1.4.)
Paragraph 6.1.1.1. now says that the formula calculates “the section width S of a tyre fitted on the measuring rim”. Before, the text said only “the section width”. The old line “S is the section width rounded to the nearest millimetre” now reads “and rounded to the nearest millimetre”. The definition of S1 now says “in millimetres” and “sidewall” in place of “(in mm)” and “side wall”. The new S1 text and the capital “W” in “Where:” come from editorial corrections that WP.29 made before the AC.1 vote. Paragraph 6.1.4. now reads “Tyre overall width specifications” in place of “Tyre section width specifications”.
Maximum outer diameter of snow tyres (para. 6.1.5.4.)
For snow tyres, paragraph 6.1.5.4. limits the outer diameter to Dmax,snow = 1.01 • Dmax, rounded to the nearest mm. In this formula, Dmax is now the maximum outer diameter established for normal use tyres. Before, the text did not say “for normal use tyres”.
Speed category of professional off-road tyres (para. 6.3.2.)
Item (c) of paragraph 6.3.2. now reads “a speed category less than or equal to 160 km/h (speed category symbol Q)”. Before, it read “a speed category ≤ 160 km/h”. The limit of 160 km/h does not change.
References to ISO 4000-1 and R.E.3 (para. 2.10. and note to para. 5.4.1.)
The definition of “Reinforced” or “Extra Load” tyres in paragraph 2.10. now refers to ISO 4000-1:2024 in place of ISO 4000-1:2021. The note to paragraph 5.4.1. no longer lists the distinguishing numbers of the Contracting Parties. It now refers to Annex 3 to the Consolidated Resolution on the Construction of Vehicles (R.E.3) for these numbers.
Q2Why it changed
- Proposed by
- Experts from the European Tyre and Rim Technical Organization (ETRTO)
- Working party
- GRBP, 81st session (February 2025)
Reasons
The proposal clarifies the structure indication in the size designation of run flat or self-supporting tyres for speeds above 240 km/h (inscription “ZRF”).
Source
“Clarification is provided for structure indication within the tyre size designation for the run flat or self-supporting tyres suitable for speeds in excess of 240 km/h (inscription "ZRF").”
The proposal changes the definition of principal grooves to remove the circular reference between this definition and the position of the tread wear indicators.
Source
“An amendment is proposed for the definition of principal grooves by eliminating the circular reference between this definition and the position of tread wear indicators.”
The definition of tread depth is new. The requirements for special use and professional off-road tyres use it.
Source
“The definition of tread depth is introduced, which is used in the requirements for special use and professional off-road tyres.”
The proposal clarifies the definition of nominal rim diameter, the calculation of tyre section width and the Dmax requirement for snow tyres.
Sources (3)
“The definition on nominal rim diameter is clarified.”
“The calculation of tyre section width is clarified.”
“The Dmax requirement for snow tyres is clarified.”
The reference to ISO 4000-1 is updated to the latest edition, ISO 4000-1:2024, which was published in March 2024.
Source
“The reference to the latest International Standard ISO 4000-1:2024 (published in March 2024) is updated.”
Document trail
- 2024-12ProposalECE/TRANS/WP.29/GRBP/2025/9Proposal by ETRTO
- —Amended in sessionGRBP-81-05-Rev.1Revised proposal transmitted by ETRTO at the 81st GRBP session
- —Working party adoptsECE/TRANS/WP.29/GRBP/79Session report, para. 12
- 2025-04Sent to WP.29ECE/TRANS/WP.29/2025/68Text that GRBP sent to WP.29 and AC.1
- —Amended in sessionECE/TRANS/WP.29/1186WP.29 editorial corrections to para. 6.1.1.1. before the AC.1 vote
- 2025-06WP.29 adoptsECE/TRANS/WP.29/1186Adopted at the 196th session (session report, para. 111)
- 2026-01-11In forceC.N.22.2026.TREATIES-XI.B.16.30UN depositary notification
Q3Who is affected
Vehicle manufacturer
- Compare the tyre size designations in your vehicle documents with the “ZRF” inscription of paragraph 2.25.3.4.1.
- Update vehicle documents that quote ISO 4000-1:2021 for “Reinforced” or “Extra Load” tyres.
Component supplier
- Mark run flat or self-supporting tyres for speeds above 300 km/h with “ZRF” in place of “RF” (para. 2.25.3.4.1.).
- For run flat or self-supporting tyres with speed-category symbol “W” or “Y”, choose “RF” or “ZRF” (para. 2.25.3.4.1.).
- Make sure that you calculate the section width S for the tyre fitted on the measuring rim (para. 6.1.1.1.).
- When you calculate Dmax,snow for snow tyres, use the Dmax established for normal use tyres.
- Update your technical documents to the new definitions in paragraphs 2.19., 2.19.1., 2.19.2. and 2.39.
Technical service / Approval authority
- During approval, compare the “RF” or “ZRF” inscription with the speed category of the tyre (para. 2.25.3.4.1.).
- Use the central zone definition in paragraph 2.19.1. to identify principal grooves.
- Measure the tread depth as the depth of the principal grooves (para. 2.39.).
- For “Reinforced” or “Extra Load” tyres, take the standard inflation pressure of the corresponding standard version tyre from ISO 4000-1:2024.
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ⓘ This report gives advice only. It is not legal or type-approval advice.