The peak and sliding braking force coefficients for radial- and bias-ply tires were compared at car speeds between 30 and 80 mph on a range of wet surfaces. Both winter and normal, siped (all-purpose) treads were used. The differences produced by the type of tire construction were not greatly influenced by the type of tread. The radial-ply tires gave higher peak braking force coefficient on all surfaces than did the bias-ply tires. Generally, the differences were independent of speed and were least on coarse-textured surfaces and greatest on fine-textured surfaces. (the differences ranged from almost 0 to 0.1.) The sliding braking-force coefficients were higher for the radial-ply tires than for the bias-ply tires on the fine- textured surfaces for the bias-ply tires on the fine- surfaces but lower (worse) on the coarse-textured surfaces. The maximum difference was about 0.05. The peak values of braking force were obtained before sliding began, the difference between the peak and sliding values being particularly marked at the high speeds. This emphasizes the potential value of anti-locking brakes.
Samenvatting