Trrl Lr 803

1000 cars as used on the roads and 100 cars in breaker yards were examined for brake system defects by an engineer of Automotive Products Ltd under contract to the Laboratory. The object was to indicate the extent of defects occuring in different components of the systems and the factoras which may contribute to the number of defects. 28 percent of the 1000 cars had one or more wheels considered to be out of adjustment or to have inoperative adjusters and 40 percent had other defects. None of 584 cars given a performance test however failed to reach the legal minimum requirement for the service brake of 0.5g. Of the factors considered age, mileageand periodic servicing appeared to affect the number of defects. The frequency of periodic servicing however, did not appear significant. The effects of these defects on brake performance and stability are considered and suggestions are made for reducing their frequency. Conclusions are reached on the necessity for improvements for improving safety by comparing these findings with those of cars involved in accidents. An accident study suggested three percent of accidents might be attributed to poor braking and these were mostly loss of control. This report suggests that a higher standard for braking deceleration in service would lead to reductions in impact speeds in many accidents