1. Home
  2. TRID
  3. View Record
https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

ACCIDENT HAZARDS AND BRAKE FORCE DISTRIBUTION IN PASSENGER CARS

OLYCKSRISKER OCH BROMSKRAFTFOERDELNING I PERSONBILAR

In rear wheel lock up before the front ones during braking, the car will spin around by itself. Therefore, car chassis designers distribute the brake force to prevent this kind of instability with normal tyres and road surface conditions. The demands are specified in vehicle regulations. However, the brake force distribution may vary when brake linings are changed or due to corrosion and insufficient maintenance. Many skidding accidents seem to have been triggered by violations of the stability requirements in legislation. It has not been possible to check the wheel lock sequence in the periodic vehicle inspection, since the plants of ASB (Motor Vehicle Inspection Company) only have low speed roller dynamometers measuring the brake forces separately on front and rear axles with stationary vehicle. Therefore, ASB installed a computerized four-platform tester at their Linkoeping plant. It was used to measure and record both braking and normal forces from all four wheels simultaneously at average speeds in the interval 10-50 km/h. More than 1000 passenger cars were sampled randomly from the ordinary inspections. While driven on the platforms by specially trained inspectors, the cars were braked at two different deceleration levels. In addition, 160 light trucks were tested. More than 10% of the passenger cars and almost 40% of the light trucks had a rear biased brake force distribution even at a moderate deceleration (average about 0.5 g i.e. 50% of gravity). For these vehicles, the risk of spinning around is considerable, for example on wet asphalt. With harder braking and greater road friction the unstable portion of the vehicle population would probably be even greater due to the increase in dynamic load transfer from the rear wheels.

Language

  • Swedish

Media Info

  • Features: References;
  • Pagination: 25 p.
  • Serial:
    • VTI MEDDELANDE
    • Issue Number: 768
    • Publisher: Swedish National Road and Transport Research Institute (VTI)
    • ISSN: 0347-6049

Subject/Index Terms

Filing Info

  • Accession Number: 00749413
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Files: ITRD
  • Created Date: Jun 26 1998 12:00AM