The effects of vehicle speed and type of road surface on tire longitudinal slip and on brake stopping distanceare investigated.The experimental work for measuring the tire longitudinal slip involved driving a passenger car for a distance of 500m on asphalt and earth roads at five different speeds varying from 20-100km/h. The number of wheel revolutions to travel this distance at each speed and on both roads was measured using a wheel revolution counter specially developed for this purpose. This data was used to calculate the tire longitudinal slip at each speed and on both roads.
The experimental work also involved measuring the brake stopping distance at five different vehicle speeds(similar to above) and on both roads. In addition to that, the effect of using Anti-lock Brake System (ABS) on the brake stopping distances was also investigated.
Test results indicate that the tire longitudinal slip and brake stopping distance are both directly proportional to vehicle speed, and they are significantly higher on earth road than they are on asphalt.
The increase of vehicle speed from 20 km/h to 100 km/h resulted in a massiveincrease in tire slip by approximately 3.6 times.For the same increase in vehicle speed, the increase in stopping distance is even more significant;it increased by approximately 15 and 18times on asphalt and earth roads respectively.
The effect of type of road surface is indicated by the fact that at 100 km/h the tire longitudinal slip and the brake stopping distance on earth road are higher than those on asphalt by 54% and 29% respectively.
Finally, test results indicate that the use of ABS has adverse effects on the brake stopping distance. At 100 km/h the stopping distance increased by 6.7% and 11.3% on asphalt and earth roads respectively as a result of using ABS.