What is the main factor determining the grip of a tractor's tyres on a dry road?
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Correct answer
B. The type of surface of such road.
Explanation
In the photo, it is a sunny day, the roadway is dry, and a blue agricultural tractor is driving in front of us. The grip of a tractor's tyres on a dry roadway depends mainly on the type of its surface - answer B.
Grip is the force with which a tyre "holds" the road - it determines whether the tractor will move off, turn and brake the way you want. Even in dry conditions, different surfaces grip differently: rough asphalt and concrete best, polished asphalt or old cobblestones clearly less well, and loose gravel or sand worst. The condition of the tread and the tyre pressure also count. The engine power (answer A) determines how hard the wheels can pull, but when the force exceeds the grip, the wheels simply spin. The efficiency of the steering system (answer C) affects the precision of turning, not how the tyre holds the roadway. When you drive from asphalt onto cobblestones or gravel, slow down and brake more gently.
Legal basis: Art. 19 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)