UN R90 Supplement 8 (02 series) · UNECE Regulation No. 90 (ECE R90) — Uniform provisions concerning the approval of replacement brake lining assemblies, drum-brake linings and discs and drums for power-driven vehicles and their trailers.
UN R90 — Supplement 8 to the 02 series of amendments
Supplement 7 → 8
- What changed
- Annex 15 has new definitions of “bell mounting face” (para. 1.5.) and “reference disc” (para. 1.6.).
- Braking surface lightening (para. 2.3.) now depends on the ratio of vehicle kinetic energy to the mass of the disc braking surface. This ratio must be the same or higher than the reference disc, with tolerance of – 20 per cent maximum.
- The disc diameter ranges in the paragraph 2.9. table and in Table A14/2.2.5. are now ≥ 150 < 250 mm and ≥ 250 < 350 mm.
- Why
- According to the proposal, Annex 15 is complex to implement. The contextual application of its nine criteria generates a huge number of disc groups, some consisting of only a single disc.
- The proposal aims at simplifying the definition of disc groups and reducing their number, while providing the same guarantees from a technical point of view.
- According to the proposal, Annex 15 does not clearly define how to choose the reference disc for disc grouping.
Q1What changed24 changes
Tangential force by disc diameter (Annex 14, Table A14/2.2.5.)
Table A14/2.2.5. now has two disc diameter ranges: ≥ 150 < 250 mm and ≥ 250 < 350 mm. Before, it had four: ≥ 150 < 200, ≥ 200 < 250, ≥ 250 < 300 and ≥ 300 < 350 mm. The new ≥ 150 < 250 mm range uses the thickness bands and minimum tangential forces that applied before to ≥ 200 < 250 mm discs. The new ≥ 250 < 350 mm range uses those that applied before to ≥ 300 < 350 mm discs.
New definition of bell mounting face (Annex 15, para. 1.5.)
Annex 15 has a new paragraph 1.5. It defines “Bell mounting face” as the surface of a brake disc that goes in contact with wheel hub. The mounting surface is calculated between the disc inner diameter T(i) and a diameter T(o). T(o) is the max diameter of area subjected to flatness restrictions as indicated on disc drawing. In case indications on the drawing are missing, T(o) = T(k) + B + 10mm. A new Figure 1 is part of paragraph 1.5.
New definition of reference disc (Annex 15, para. 1.6.)
Annex 15 has a new paragraph 1.6. that defines the reference disc within each discs group. It is the disc with the highest ratio of kinetic energy (considering all the replacement applications foreseen) and its mass, as described in paragraph 5.3.6.
Braking surface lightening (Annex 15, para. 2.3.)
Braking surface lightening under paragraph 2.3. now depends on the ratio of vehicle kinetic energy to the mass of the disc braking surface. This ratio must be the same or higher than the reference disc, with tolerance of – 20 per cent maximum. Any lightening solution (holes, slots, wave, etc.) is still allowed, provided that this ratio condition is met. A new example shows how to calculate the Braking Surface Mass (BSM) and the Braking Surface Lightening (BSL) ratio (K.E. / BSM).
Spokes of the bell (Annex 15, para. 2.6.)
Paragraph 2.6. still measures the full/empty ratio of the bell spokes on the average circumference. This circumference is now taken between end of the mounting face and max. diameter of the bell. Before, the end point was the beginning of the braking surface. The full/empty ratio is now same or higher than the reference disc (with a tolerance of -20 per cent max.). The thickness is now same or higher than the reference disc (with a tolerance of -15 per cent max). Before, the ratio was within the range ± 20 per cent and the thickness within the range (+ 30 per cent) ÷ (– 10 per cent).
Outer diameter ranges (Annex 15, para. 2.9.)
Paragraph 2.9. now reads “Outer diameter included in the range of 100 mm”. Before, the range was 50 mm. The table in paragraph 2.9. now has two ranges, ≥ 150 < 250 mm and ≥ 250 < 350 mm, instead of four. Each range still applies to one piece, composite fixed and floating discs.
Q2Why it changed
- Proposed by
- Expert from Italy
- Working party
- GRVA, 11th session (September 2021)
Reasons
Some important shortcomings were found while implementing UN Regulation No. 90 for the approval of replacement discs for motorcycles. Annex 15, which defines criteria for the discs grouping, is complex to implement. The contextual application of the nine criteria generates a huge number of groups, some consisting of only a single disc.
Sources (2)
“Some important shortcomings were found, while implementing UN Regulation No. 90 (for the approval of replacement discs for motorcycles).”
“the contextual application of the nine criteria for the definition of disc groups generates a huge number of groups (some consisting of only a single disc).”
The expert from Italy introduced the proposal at GRVA. He explained that Annex 15 was leading to a high number of groups to be tested. Due to the grouping criteria, this was inducing an overproportioned test workload.
Source
“He explained that Annex 15 was leading to a high number of groups to be tested and therefore was inducing an overproportioned test workload due to the grouping criteria.”
The proposal keeps the same nine criteria. It also allows discs with a different geometry in the same group. This applies as long as the disc itself is subject to lower thermal and mechanical stresses than the reference disc. It aims at simplifying the definition of disc groups and reducing their number, while providing the same guarantees from a technical point of view.
Sources (2)
“This proposal, while maintaining the same nine criteria, also allows discs with a different geometry to be included in the same group as long as the disc itself is subject to lower thermal and mechanical stresses than the reference disc.”
“This proposal therefore aims at simplifying the definition of disk groups, reducing their number, while providing the same guarantees from a technical point of view.”
Annex 15 does not clearly define how to choose the reference disc for disc grouping. The disc to be tested could be different from the reference disc used for disc group definition. The condition is that the tested disc is the one subject to the highest braking torque and to the largest energy to be absorbed.
Sources (2)
“Annex 15 does not clearly define how to choose the reference disc for disc grouping”
“The disc to be tested could be different from the reference disc used for disc group definition, provided that it is the one subject to “the highest braking torque and to the largest energy to be absorbed”.”
Document trail
- 2021-07ProposalECE/TRANS/WP.29/GRVA/2021/28Proposal by the expert from Italy
- —Working party adoptsECE/TRANS/WP.29/GRVA/11Session report, para. 101
- 2021-12Sent to WP.29ECE/TRANS/WP.29/2022/17Text that GRVA sent to WP.29 and AC.1
- 2022-03WP.29 adoptsECE/TRANS/WP.29/1164Adopted at the 186th session (session report, para. 132)
- 2022-10-08In forceC.N.346.2022.TREATIES-XI.B.16.90UN depositary notification
Q3Who is affected
Vehicle manufacturer
- No direct action for this role.
Component supplier
- Identify the reference disc of each disc group as defined in Annex 15, paragraph 1.6.
- Review your disc groups against the changed criteria in Annex 15, paragraphs 2.3., 2.6. and 2.9.
Technical service / Approval authority
- Use the changed Table A14/2.2.5. for force F in Annex 14.
- Be ready to assess disc groups under the changed Annex 15 criteria in paragraphs 2.3., 2.6. and 2.9.
See every change side by side
RegVault customers compare every version of UN regulations, read the consolidated text and download the PDF.
ⓘ This report gives advice only. It is not legal or type-approval advice.