STUDY ON THE EFFECTIVENESS OF WINTER TIRES IN SUMMER CONDUCTED BY CAA-QUEBEC

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Fay Boone
7 years ago
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1 STUDY ON THE EFFECTIVENESS OF WINTER TIRES IN SUMMER CONDUCTED BY CAA-QUEBEC September 2008

2 1. Introduction The study aimed to assess as accurately as possible the effectiveness of winter tires used in summer in comparison with that of all-season tires used in the same period. The results of the study were derived from two different tests the avoidance test and the emergency braking test conducted at the PMG Technologies Test and Research Centre at Blainville. 2. Protocol Tires All tests were conducted using the same car, with the same driver always at the wheel. The car was equipped first with four new all-season tires inflated to the pressure recommended by the manufacturer. Once the tests were completed on the all-season tires, these were replaced by new winter tires with a speed rating identical to that of the all-season tires just tested, and inflated to the same pressure. Surfaces The tests were conducted on two different surfaces at two different locations of the test centre: on dry pavement and wet pavement. In both cases, the width of the test corridor was equal to the normal width of a traffic lane. Both surfaces were flat and almost perfectly even, though it should be noted that the wet pavement had a special type of coating that, even when dry, is slightly more slippery than ordinary asphalt. We did not take this variable into account in the test results, since readings from wet and dry pavement were never compared directly in the study. Conditions During the trials, the weather was dry and sunny, with a few windy episodes. The temperature was about 20 C. For the emergency braking tests, the braking distance measurements were taken using a computer specifically designed for this type of study, a Vericom VC3000. Throughout the test, the car s fuel tank was kept at its fullest level. - 1/5 -

3 3. The testing process The session began with avoidance tests using all-season tires on dry pavement. The driver had to reach a speed of 50 km/h before conducting the avoidance manoeuvre. The test was repeated several times, each time at a slightly higher speed. The same test was then conducted on wet pavement. After that, the car was equipped with winter tires, and the avoidance tests were redone under the same conditions as with the all-season tires. The braking tests involved reaching a pre-established speed stabilized by means of a speed regulator and validated with a GPS before hitting the brakes hard and using the Vericom VC3000 to measure the distance covered by the car before it came to a full stop. Here as well, the exercises were conducted with both types of tire and on both types of pavement. The emergency braking measurements were taken at speeds of 50, 70, 90 and 100 km/h. 4. Results and observations BRAKING IN METRES DRY WET km/h all-season winter difference % all-season winter difference % (2) (1) AVERAGE 2.4 (3) 9.8 (3) 11.9 (4) 26.2 (4) (1) The greater disparity can be attributed to differences in the surface texture, even using the same four-metre-wide lane, and to variations in the functioning of the ABS system. (2) The greatest disparity can be attributed to differences in the surface texture, even using the same four-metre-wide lane, to variations in the functioning of the ABS system, and to a water layer that was thicker because the wind had stopped blowing during this test. (3) Does not take account of the test at 90 km/h. (4) Does not take account of the test at 70 km/h. - 2/5 -

4 AVOIDANCE DRY WET km/h all-reason winter all-season winter 50 OK 55 OK 60 OK 65 OK 70 OK 75 OK already some instability instability instability 80 OK 1 becoming harder to control OK; 1 the car starts sliding, especially at the rear OK; 1 almost loss of control and a cone knocked over OK OK OK 1 OK, 1 but a sense of being near the limit OK, 1 but a sense of being near the limit already some instability instability instability instability and instability and and a cone knocked over 1 Difficult to do this manoeuvre. - 3/5 -

5 5. Conclusion Winter tires are clearly less well adapted to summer use, since they have longer braking distances and make avoidance manoeuvres more difficult in emergencies. Moreover, the results were recorded at an outdoor temperature of 20 C, which is lower than temperatures encountered during the warmer summer months. - 4/5 -

Tyre Awareness Training

Tyre Awareness Training Tyre Law Tread depth Tyres on cars, light vans (not exceeding 3,500kg gross weight) and light trailers must have a tread depth of at least 1.6mm across the central three-quarters