UN R75 Supplement 21 (00 series) · UNECE Regulation No. 75 (ECE R75) — Uniform provisions concerning the approval of pneumatic tyres for L-category vehicles.
UN R75 — Supplement 21 to the 00 series of amendments
Supplement 20 → 21
- What changed
- The category of use “special tyre” is now “special-use tyre”, and new paragraph 2.33.1. defines “Normal tyre” as a tyre intended for normal, on-road use.
- For sizes not included in Annex 5, the overall width percentages now list moped tyres together with normal tyres and snow tyres (para. 6.1.4.2.).
- In Annex 9, snow and special-use tyres with speed-category symbol V/W now have the H dyn value H × 1.21.
- Why
- The proposal is to align the categories of use with UN Regulations Nos. 30 and 54 and to introduce a definition of “normal tyre”.
- The proposal is to add provisions for the dimensional requirements of moped tyres.
- The proposal is to add a factor for the centrifugal radius of snow tyres and special-use tyres with a speed category above 210 km/h.
Q1What changed88 changes
Category of use: “Normal tyre” and “Special-use tyre” (paras. 2.1., 2.33. and 3.1.10.)
Item (c) of paragraph 2.1. now lists the categories of use as normal tyre, snow tyre, special-use tyre, moped tyre and all terrain (AT) tyre. New paragraph 2.33. reads “Category of use:”, and new paragraph 2.33.1. defines “Normal tyre” as a tyre intended for normal, on-road use. Former paragraph 2.40. is now paragraph 2.33.3., and its defined term “Special tyre” is now “Special-use tyre”. Former paragraph 2.34., which said that “MST” means “multiservice tyre”, suitable both on and off road, is deleted. Paragraph 3.1.10. now gives the inscription “MST” in the case of special-use tyres, in place of “in the case of multiservice tyres”. Paragraphs 3.1.9., 4.1.3. and 4.1.3.1., Annex 1 item 4.2 and footnotes of Annex 5, Tables 1(a), 2, 3 and 4 now use the new names.
Nominal rim diameter (paras. 2.20.5., 2.21. and 2.21.1.)
Paragraph 2.21. now defines “Nominal rim diameter” as a conventional number denoting the diameter of the rim on which a tyre is designed to be mounted. The diameter of the rim is expressed either by code (numbers below 100) or in millimetres (numbers above 100) but not both. Before, paragraph 2.21. defined “Nominal rim diameter (d)” as the diameter of the rim on which a tyre is designed to be mounted. Paragraph 2.20.5. now reads “the nominal rim diameter;”, in place of a description of the conventional number “d”. Former paragraph 2.20.5.1. is now paragraph 2.21.1. It gives the values of the “d” symbol in millimetres when the nominal rim diameter is expressed by code.
The suffix “M/C” in Annex 3 and in Annex 5, Table 7 (para. 2.20.6.)
Paragraph 2.20.6. covers the suffix “M/C” for tyres intended to be fitted on rims designed for motorcycles. The suffix now comes after the nominal rim diameter, as shown in the example in Annex 3. Item (a) of Annex 3 now gives the grouped example as “100/80 B l8 M/C”, in place of “100/80Bl8”. The Annex 3 example now also includes the line “b = 4 mm min.”. The Table 7 footnote now says that tyres in bias-belted construction must be identified by the letter “B” in place of “-”. In Table 7, rows MU90-15, MV90-15, MU85-16 and MV85-15 no longer show “M/C” in the tyre-size designation.
Section width and the Annex 5 table values (paras. 2.24., 6.1.1.1., 6.1.1.2. and 6.1.2.2.)
Paragraph 6.1.1.1. now names the section width S of a tyre fitted on the measuring rim. The calculated section width must now be rounded to the nearest millimetre. Paragraphs 6.1.1.2. and 6.1.2.2. cover tyres whose tyre-size designation is shown in the first column of the Annex 5 tables. For these tyres, the section width and the outer diameter now must be the values given opposite the tyre-size designation in the tables. Before, the text said that these values were allowed. In the “Measuring rim” definition (para. 2.24.), the words “for size measurements” are now “for the measurement of the tyre dimensions”.
Overall width and outer diameter by category of use (paras. 6.1.4. and 6.1.5.)
Paragraph 6.1.4. now has the title “Tyre overall width specifications”. For sizes not included in Annex 5, item (b) of paragraph 6.1.4.2. now gives the percentages in a table by category of use. For normal tyres, snow tyres and moped tyres, the percentage is 8 % (rim diameter code 12 and below) or 10 % (code 13 and above). For special-use tyres, it is 25 %. Before, paragraph 6.1.4.2.2. gave 25 per cent for special service tyres which are suitable for limited road use and are marked MST. In the tables for the factors a and b (paras. 6.1.5.2.1. and 6.1.5.2.2.), moped tyres now have the values of normal tyres.
H dyn values for the centrifugal growth test (Annex 9)
The Annex 9 table gives the limit values H dyn for the enveloping curve of the centrifugal growth test. For speed-category symbols V/W, snow and special-use tyres now have the value H × 1.21. Before, the table had a row “Over 210 km/h” with no value (“-”) for snow and special tyres. The heading of the first column is now “Speed-Category Symbol”, and the values use “×” and a decimal point.
Principal grooves, terms, paragraph numbers and footnotes
Paragraph 2.14. now defines “Principal grooves” as the wide tread grooves of the tyre. Before, “Principal groove” meant the wide grooves situated in the central zone of the tread. Former paragraphs 2.37. to 2.37.6. are now paragraphs 2.35. to 2.35.6., and paragraph 6.2.1.1. and Annex 7 refer to the new numbers. Paragraphs 2.30., 2.36., 3.1.5.1., 3.1.5.2. and 6.2.1.1., and Annexes 7 and 8 now use the terms “load-capacity index”, “speed-category symbol” or “tyre-size designation”. The footnote on the distinguishing numbers now says that they are reproduced in Annex 3 to the Consolidated Resolution on the Construction of Vehicles (R.E.3). Before, it listed the number of each country.
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 is to align the categories of use to “normal tyre”, “snow tyre” and “special-use tyre” in line with UN Regulations Nos. 30 and 54. It is also to introduce a definition of “normal tyre” and to use the terms “snow tyre” and “special-use tyre” that are already defined.
Sources (2)
“It is proposed to align the categories of use to "normal tyre", "snow tyre" and "special-use tyre" in line with UN Regulations Nos. 30 and 54”
“to introduce a definition of "normal tyre" and consequently make use of the terms "snow tyre" and "special-use tyre" that are already defined.”
Annex 5, Table 7 does not present the tyre-size designations in a consistent way. It also does not consider that there may be tyres with bias-belted structure and an alphanumeric tyre-size designation. The proposal is to present them consistently and to state explicitly that they may also be used for tyres in bias-belted structure. It is also to include the suffix “M/C” in the Annex 3 figure of the sidewall markings, and to present the markings more clearly.
Sources (3)
“Annex 5, Table 7 does not present the tyre-size designations in a consistent way and does not consider that there may be tyres with bias-belted structure”
“present the tyre-size designations in a consistent way and to provide explicitly that tyre-size designations from this table may also be used for tyres in bias-belted structure.”
“in the figure illustrating the sidewall markings in Annex 3 and to present the markings in a clearer way.”
The proposal is to add provisions for the dimensional requirements of moped tyres. It is also to add a factor for the centrifugal radius of snow tyres and special-use tyres with a speed category above 210 km/h.
Sources (2)
“It is proposed to add provisions for the dimensional requirements of moped tyres.”
“It is proposed to add a factor for the centrifugal radius of snow tyres and special-use tyres with a speed category above 210 km/h.”
Proposer's reason (informal document GRBP-81-07-Rev.1)
For moped tyres, the proposal uses the same factors as for normal tyres, because it is the current practice for type approval. The proposed value for parameter H is the one standardised by ETRTO. It is in line with the criteria for the other speed-category symbols (+5% with respect to normal tyres).
Submitted by Experts of ETRTO. Working party adoption: ECE/TRANS/WP.29/GRBP/79, para. 14.
Sources (2)
“It is proposed to use the same factors as for normal tyres because it is the current practice for type approval.”
“The proposed value for parameter H is the one standardised by ETRTO and in in line with the criteria used for the other speed-category symbols (+5% with respect to normal tyres).”
Proposer's reason (informal document GRBP-81-07-Rev.1)
The proposal is to amend the definition of principal grooves to consider the specificity of motor cycle tyres. The definition of “MST” overlapped with the definition of “special tyre” (former paragraph 2.40), and the marking requirement overlapped with paragraph 3.1.10.
Submitted by Experts of ETRTO. Working party adoption: ECE/TRANS/WP.29/GRBP/79, para. 14.
Sources (3)
“It is proposed to amend the definition of principal grooves for considering the specificity of motor cycle tyres”
“The definition of "MST" overlapped with the definition of "special tyre" (Former paragraph 2.40).”
“The marking requirement overlapped with paragraph 3.1.10.”
Document trail
- 2024-12ProposalECE/TRANS/WP.29/GRBP/2025/11Proposal by ETRTO
- —Amended in sessionGRBP-81-07-Rev.1Revised proposal transmitted by ETRTO at the 81st GRBP session
- —Working party adoptsECE/TRANS/WP.29/GRBP/79Session report, para. 14
- 2025-04Sent to WP.29ECE/TRANS/WP.29/2025/72Text 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. and Annex 5, Table 7 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.29.2026.TREATIES-XI.B.16.75UN depositary notification
Q3Who is affected
Vehicle manufacturer
- No direct action for this role.
Component supplier
- Where you mark “M/C”, place it after the nominal rim diameter, as shown in the Annex 3 example (para. 2.20.6.).
- For Table 7 sizes in bias-belted construction, use “B” in place of “-” (for example MM90 B 19 M/C).
- Make sure that snow and special-use tyres with speed-category symbol V/W meet the new H dyn value H × 1.21.
Technical service / Approval authority
- Be ready to use H × 1.21 as the H dyn value for snow and special-use tyres with speed-category symbol V/W.
- Where “M/C” is marked, check that it comes after the nominal rim diameter (para. 2.20.6.).
- Check that Table 7 sizes in bias-belted construction use the letter “B” in place of “-”.
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ⓘ This report gives advice only. It is not legal or type-approval advice.