ASSYMETRIC BRAKE FORCE DISTRIBUTION-CAUSING MECHANISMS AND THE EFFECT ON STRAIGHT LINE RUNNING STABILITY AND HANDLING DURING BRAKING

The investigation consists of two studies, one concerning brake defects and one concerning the effect of asymmetric brake force distribution on straight line running stability and handling during braking. The brake defect investigation concerned change in brake efficiency due to locked wheel brake cylinders and water, brake fluid or transmission oil contaminated brake linings. The tests were carried out on a large diameter roller type brake tester. The brakes were mounted on vehicles. Tested brake types were disc brakes and duo servo duplex and simples drum brakes on four Swedish cars. The results showed that considerable changes in brake efficiency both upwards and downwards can occur. The investigation concerning the effects of asymmetric brake force distribution was carried out with four cars with different weight distribution. The tests were straight line braking tests on dry asphalt from 80 km/h. The vehicles were braked with an automatic braking device. The tests were performed with locked handwheel, steering correction from the driver and steering correction by an automatic steering device. The results showed that asymmetric brake force distribution can give course deviations in spite of the drivers corrective efforts which are judged as a traffic hazard. Front wheel brake asymmetry gave the largest effects in combination with high load on the rear wheels. Steering effects from the rear axle due to elasticities in the suspension also turned out to be a potential hazard. /Author/