Abstract
ABSTRACT - CITA Working Group 5, is responsible for the development and communication of the expertise in brake testing procedures during periodic inspection. Main working items: Brake performance of heavy good vehicles, Interrogation to the electronic systems, Additional checks, CITA Recom No. 8 & CITA Brake Questionnaire The WG is responsible for the CITA Recommendation No.8 on Brake Testing that, when applicable, makes reference to international standards (e.g. ISO) Assessment of Brake performance of Heavy Vehicles. Brake type approval consist of a number of dynamic brake test mostly with laden vehicle. The brake test procedures for PTI have to verify in a cost-effective manner, the actual brake performance of the in-use vehicle compared to the approval requirements. The realistic method would be the fully laden roller test, but in many cases / countries, testing laden vehicles is not possible. (the system do work in some countries) Alternative methods have to allow the assessment of the laden brake performance by measuring the unladen vehicle by calculations or extrapolations (All extrapolation methods require the simultaneous measure of air pressure in the brake cylinder): Existing methods to be used in PTI on Roller Brake Tester: Fully Laden vehicle test, One point extrapolation, Two point extrapolation, Multipoint extrapolation, Reference brake forces According to ECE Reg. No.13 for Brake system homologation, the reference brake forces system was defined: At the time of type approval, the vehicle manufacturer declares the brake forces in the tyre periphery vs the air pressure in the brake cylinder. No need to extrapolate. Brake assessment is a direct comparison between actual measurements and reference values. Brake compatibility between tractor and trailer during PTI. Differences in the brake force between tractor and trailer axles for a given brake signal by the driver can be due to illegal manipulation or deterioration of the air system. Predominance is checked by measure of brake signal (e.g. air pressure in the front axle cylinder) vs the pressure sent to the trailer after the control trailer valve (signal coupling head).
KEYWORDS – Brake test, Roller bench tester, Reference brake forces, Extrapolation methods, Braking compatibility