# Commission Delegated Regulation (EU) 2015/68 of 15 October 2014 supplementing Regulation (EU) No 167/2013 of the European Parliament and of the Council with regard to vehicle braking requirements for the approval of agricultural and forestry vehicles (Text with EEA relevance), Division 2.4: Symbols valid for hydraulic-transmission braking systems (see Figure 8 of Appendix 1)

Extent: E+W+S+N.I.

2.4.1. ih reduction ratio between travel of coupling head and travel of piston in master cylinder;
2.4.2. i′g reduction ratio between travel of cylinder thrust point and lift (application travel) of brake-shoe centre;
2.4.3. FRZ surface area of piston of one wheel cylinder for drum brake(s); for disc brake(s), sum of the surface area of the caliper piston(s) on one side of the disc;
2.4.4. FHZ surface area of piston in master cylinder;
2.4.5. p hydraulic pressure in brake cylinder;
2.4.6. po retraction pressure in the brake cylinder when the towed vehicle moves forward; i.e., in graph of M = f(p), the value of the pressure p at the point of intersection of the extrapolation of this function with the abscissa (see Figure 7 of Appendix 1);
2.4.6.1. por brake retraction pressure when the towed vehicle moves rearward (see Figure 7 of Appendix 1 );
2.4.7. p* hydraulic pressure in the brake cylinder to produce the braking force B*;
2.4.8. pT test pressure according to point 6.2.1:
2.4.9. ρ′ characteristic of the brake when the towed vehicle moves forward as defined from:
M = ρ′ (p – po)
2.4.9.1. ρ′r characteristic of the brake when the towed vehicle moves rearward as defined from:
Mr = ρ′r (pr – por)

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Source: https://www.legislation.gov.uk/eur/2015/68/annex/VIII/division/2/division/2.4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2015-68/annex-VIII/division-2/division-2.4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.