IF NOT, BUT VERY WANTED
In winter, even the roads are covered with snow and ice. Measurement results of accelerating and braking dynamics of the car, in contrast to those obtained on dry asphalt concrete, are now valid only for specific test conditions. After all, the coating on the winter road is unstable, temperature and humidity in the cold season also change very often. The coefficient of adhesion of tires on a snowy or icy test track not only decreases significantly, but also “floats” in a very wide range - from about 0.2 to 0.6. It is clear that the acceleration time to 100 km / h or the elasticity of the car will be completely different than on dry asphalt.
Of course, by creating ideal, or rather, equal conditions, machines can be compared: on completely flat ice, with absolutely identical tires … So what do we get? We define the best in the “hockey player” nomination … Moreover, measurements of acceleration and braking dynamics in winter characterize not only the capabilities of the car, but also the characteristics of the tires and the level of driver training.
By the way, on the familiar snow-salt substance that covers general roads, the coefficient of adhesion varies in an even wider range, and not only depending on temperature and humidity, but also on traffic intensity. Naturally, a car even on good winter tires becomes poorly predictable, especially for inexperienced drivers. However, enough reasoning. Let’s do the testing. It’s better to see once …
The editorial Toyota Corolla is invited to the ice and snow of a dynamometer road! We have already talked about the requirements for the tester (ЗР, 2004, No. 10). For example, in five races on a dry road, the spread of indicators should be no more than 5%. On heterogeneous snow and ice, it is quite difficult to achieve this even for a professional.
So, the tire pressure (studded winter) is checked, the equipment is tuned …. Temperature - minus 9, coating - rough ice with snow. And now the car flies along the road, "twirling snow whirls." Beautiful, of course! And what do the appliances show?
Up to 100 km / h the car accelerates more than two times slower than in summer (see table). Up to 40 km / h - 4.2 times! It would be nice to remember this when crossing an unregulated intersection or overtaking. But the most significant is the braking dynamics. Toyota lost to herself more than … 113 m! We hope this experience is useful to someone.
But not for comparative tests of cars, where we want to understand their maximum capabilities. One car will slip on 153 m, the other on 155 - so we will more likely assess the danger of a dashing ride.
So, we repeat: for testing according to the standard program, you will have to wait for spring. But in the cold we carry out special tests: winter tires, four-wheel drive transmissions of various designs, ABS, traction control and other modern systems designed to "show the class" in such conditions. It is important that these tests are comparative.
For winter tests, they prepare a section of the road with the most uniform coating, whether it is ice, rolled or loose snow. By the way, abroad there are special winter training grounds. For example, in the polar Finnish town of Ivalo, where climatic conditions are relatively stable and low temperatures persist for a long time.
The expert qualification requirements are also more stringent than in summer. After all, the number of races is limited, because the state of coverage is changing rapidly. Well, of course, the driver is faced with the task of saving the car … when there is bare ice under the wheels. Slippery roads dictate original measurement methods. For example, in comparative tests of tires, acceleration dynamics are estimated in the range from 0 to 30 km / h or even from 5 to 35–40 km / h. This reduces the likelihood of expert driver errors and shortens the test section of the road. In addition, depending on external conditions, the measurement results sometimes have to be corrected by comparing the data on the tested tires with a conditionally standard set - the “stove” of a particular test. The braking distance is measured not from the “summer” 100 or even 80, but from 50 km / h.