EFFECT OF RATE OF CHANGE OF SLIP ON THE PEAK BRAKING COEFFICIENT OF PASSENGER CAR TIRES

The peak braking coefficient was measured for five tires at six rates of change of slip on three wet surfaces, and a slick tire was tested on dry asphalt. The difference in braking coefficient for a tire-pavement combination over the range of rates of change of slip varied from 3.6 to 33.6 percent. In general, the effect of rate of change of slip was more pronounced with slick tires and low coefficient surfaces. In cases where statistically significant differences existed on wet surfaces, the highest coefficients occurred most often at intermediate rates of change of slip (between 36%/sec and 100%/sec), and the lower coefficients were usually measured at both very fast and very slow rates of change of slip. It is hypothesized that a reduction in the rate of change of slip causes an increase in the peak braking coefficient on a dry surface but increases the probability of partial hydroplaning on a wet surface. The balance between these two conflicting effects causes the peak braking coefficient to be maximum at intermediate rates of change of slip on many wet surfaces.

• Supplemental Notes:
  • Prepared in cooperation with Maryland Univ., College Park. Dept. of Mechanical Engineering.
• Corporate Authors:

  National Highway Traffic Safety Administration

  Safety Research Lab, 6501 Lafayette Avenue, Bldg 2
  Riverdale, MD  United States  20840

  University of Maryland, College Park

  Department of Mechanical Engineering
  College Park, MD  United States  20742
• Authors:
  • BOYD, P L
  • Walston, WHJ
• Publication Date: 1977-8

Media Info

• Pagination: 75 p.

Subject/Index Terms

• TRT Terms: Automobiles; Brakes; Braking; Coefficients; Hydroplaning; Passenger vehicles; Pavements; Skid resistance; Slip (Fluid mechanics); Tires; Traction; Wet weather
• Uncontrolled Terms: Wet pavements
• Old TRIS Terms: Slip coefficient
• Subject Areas: Highways; Pavements; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00167042
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: DOT-HS-802513 Tech Rpt., T-1018
• Files: NTIS, TRIS, USDOT
• Created Date: Oct 29 1978 12:00AM