An Evaluation of European Peak Mu and Braking Efficiency Test Procedures

Efforts to develope a harmonized brake standard have led to the developement and evaluation of procedures for measuring the brake balance and braking efficiency of passenger cars. The European braking regulations include a procedure for direct measurment of the braking efficiency of a vehicle equiped with an antilock system (ECE Regulation No. 13. Annex 13/EEC Directive 71/320 Annex X). The procedure is a two step process including the measurement of the peak coefficient of friction (mu) for the vehicle tire on the test surface, and then finding the maximum deceleration of the vehicle on the test surface for calculation of the braking efficiency. Tests were conducted to evaluate the feasibility of using this procedure for vehicles not equiped with ABS. Comparisons were made between the peak coefficient of friction as measured by the Annex 13 procedure and as measured by a traction trailer with the vehicle tires installed. Comparisons were also made between the Annex 13 braking efficiency and the braking efficiency determined by measuring the brake distribution usine a Road Transducer Plate (RTP) facility and using this information in conjunction with traction trailer data and rigid body calculations.