Summer, frankly, went to our experimental pretty cold - plus 3-5 ° C, but it is even more interesting to compare tires in unusual conditions.
All world tire leaders - Bridgestone, Continental, Goodyear, Michelin, Pirelli and, of course, Nokian - have responded to our offer to participate in an unusual test. Recently, this brand has been strong not only in winter, but also in good summer tires.
The scene is the Continental summer training ground we rented. This led to some customs difficulties, but allowed to carry out such interesting tests as longitudinal and transverse aquaplaning. They first appear on the pages of ZR, so let's talk about them in more detail.
Longitudinal aquaplaning. The car moves on the water with its left wheels - a special bathtub has been made for it with a water supply system (layer thickness 8 mm), and with the right wheels on wet asphalt. The sensors on the wheels determine their speed. As soon as the difference in the sides reaches 15%, the speed of the car is fixed - this is the beginning of the ascent of the wheels above the road on a water wedge.
Cross aquaplaning is essentially the same, but when cornering. The speed of the car during the passage of the bath (here the depth is 7 mm), as well as the turning radius, is constant, the “step” of speed increase is 5 km / h. In addition to speed, the value of lateral acceleration of the car is also fixed by the accelerometer. However, the speed of ascent onset alone is not enough for a complete picture of the car’s behavior “in a puddle”. It is necessary to trace how it behaves at different speeds, how much it deviates from a given trajectory, how quickly the wheels lose traction, etc. In general, there are many criteria and therefore use one comprehensive (integrated) one. According to the test results, a graph is built of the dependence of lateral acceleration (coupling properties) on the cornering speed. Each tire manufacturer uses the obtained results in his own way, and complex indicators are somewhat different.
We applied the Continental technique, which focuses on the average lateral acceleration in the speed range 65–95 km / h. But Michelin, for example, sets the range of measurements in other coordinates - from 0.2 g for speed gain to 0.15 g for lower grip. And as a complex criterion, it takes not the average value of acceleration in this section, but the integral (the area of the figure between the obtained curve and the axis of speed limited by two values of accelerations) …