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Technical bulletins

12 SARN brake data

Category: HVEK


  • This technical bulletin replaces Memo 86.
  • This technical bulletin covers the use of brake data derived from the Australian sub assembly registration number (commonly called SARN data).


Land Transport Rule: Heavy-vehicle brakes 2006: Schedule 5: Section 11: Clauses 11.1 through 11.3 require brake data to be provided by the axle manufacturer or brake manufacturer and that the data must be based on tests carried out in accordance with one of the standards in 2.5(2) of the Rule. ADR 38 is not one of the standards in 2.5(2).

However, SARN data derived under ADR 38 is being provided, and by organisations other than axle manufacturers or brake manufacturers, and this data is being used for some brake certifications. Feedback from HVEK Certifiers has increasingly highlighted a problem with the brake factor calculated using SARN data as being unrealistically low. HVEK Certifiers then have to come up with a best-guess brake factor, usually by making a comparison with a similar foundation brake, to complete certifications. To use the SARN data unmodified results in errors of up to 30%, resulting in over-braked axles and premature brake lining wear.

Short term solution

Where axle or brake manufacturer brake data is not available but SARN data to ADR 38 is:

  1. Apply for exemption from clauses 11.1, 11.2 and 11.3 as appropriate
  2. Derive brake data from a similar (Note 1) foundation brake and use that data
  3. Obtain confirmation that the friction material on the axle is equivalent to the friction material of the brake in 2.
  4. Enter appropriate comments on the LT400 and an expiry date of six months at which time the vehicle will require re-certification using correctly established brake data.

This short term solution can only be applied to vehicles fitted with an ABS function.

This approach is available to be applied to exemption applications received from the date of issue of this Memo until 30 November 2016. That is, exemptions will not be granted for applications received after 30 November 2016.

This approach does not need to be applied retrospectively to vehicles already certified.

Long term solution

From 1 December 2016 axle and brake manufacturers and retailers must comply with their responsibilities under Clause 10.5 of the Rule.

Note 1

Geometry needs to be the same (s-cam radius, drum radius, location of shoe pivot points, etc).

Page added 24 May 2016 (see amendment details)