Is it possible to “on the fingers” explain how to drive, using the full 100% potential of tire adhesion to the road surface? Can!
To do this, we represent the forces acting on the car in turn with the help of the so-called “traction circle”, that is, the graphic circle of the clutch. To do this, draw a cross and circle it equally distant from the center. In fact, this is a graph of accelerations G in each phase of the turn: braking, moving along an arc and accelerating. Suppose that in all three phases of the tire has the same coefficient of friction, allowing you to develop lateral acceleration in 1.1G. If you exceed it, the tire will begin to slide, and this, as you know, slows down the car. In our graph, these are the points of intersection of the straight lines of the cross and the circle. The upper part of the vertical line is braking, the lower is acceleration.
The horizontal line to the right and to the left of the center is the forces in the turn. On the other hand, if the driver does not use all the tire grip capabilities, he will not be fast enough. If you fully use the ability to grip tires in turn, then the graph of lateral accelerations becomes like a circle. The trick is to carry the 1.1 G lateral acceleration through transition phases: from deceleration to movement along an arc and then into the acceleration phase, that is, on our graph exactly around the circle. In order for his first phase to flow into the second without loss, experienced riders use the “trail breaking” technique. Let me remind you that the so-called braking with a smooth release of the brake pedal simultaneously with the steering at the entrance to the turn. If during the transition from the braking phase to the phase of motion along the arc, the speed drops, even for an instant, then the value of the lateral acceleration will also fall. The potential of the tires at this point, and hence the clutch margin, will not be fully utilized 100%. An attempt to catch up in this phase of rotation is likely to be doomed to failure. Moreover, even an early depression of the gas pedal will most likely cause excessive tire slip and it will not be possible to achieve the optimal lateral acceleration value of 1.1G in the turn. The whole secret is to catch and use the optimum grip of the tires already on the braking, then smoothly move it in motion along the arc and save during acceleration in the final phase of the turn. So, to go really fast, you need to be able to use the tire grip potential at 100% in each phase of the turn. How this happens and shows our graph – the grip circumference.
Recall that a racing tire develops maximum grip when driving with a corner of 8–12%, which means that it is at the very beginning of the slip. It should be so, but in what phase of the rotation does this slide begin? At the beginning racer, as a rule, only at the exit from the turn. In the “pros” – already at the entrance.
Even earlier, on braking. “Treshold bracking” is a method of aggressive braking, in which the wheels are not locked, but turn much slower. Their slippage at this point provides maximum traction mode. All the art of a top-class racer is that from that moment on and up to the exit of the turn, the tires are in exactly this state (we are talking about ninety degrees of turns and close to them on the slope). The minimum correction by the wheel, gas and brakes allows you to maintain the optimum angle of withdrawal, that is, to keep the tires in maximum clutch mode in all phases of the turn. This is movement on the edge or in the optimal mode. On the brink of which dream newcomers and which is very clearly seen from the coach or attentive fan. In the first turn of the slow ligament, it is clearly seen that the leaders’ cars “drive” a little (or slightly rearrange) from the point of entry into the turn and to its top. This is the effect of correctly accepting the entrance into a turn along the so-called “slow down” trajectory, which means continuing braking almost to the turn apex. Machines of slower pursuers are “driven”, as a rule, only in the second part of the turn, that is, at the exit from it, and that is another matter.
It is easy for one rider to feel the tire grip limit, for another it can be a big problem. In other words, one racer can use 100% tire grip in the optimum mode for as long as possible in absolute terms. Then you can slide as little as possible and, what is very important, drive the car at the limit, that is, on the verge, even if not along the optimal trajectory. That is, in each phase of each turn throughout the race. This is a special racing talent, God’s gift, if you want. And the other (or others) it does not always work, but occasionally, depending on the circumstances. The first driver is none other than Michael Schumacher, and the given example is the secret of his victories. For the above reason, its speed in the initial phase of the entrance to the turn and in the average is 1-2 km / h higher than that of the other racers, therefore, acceleration starts a little earlier. As a result, the speed of exit from turns and at the end of each straight line rises.