How will you achieve the greatest efficiency of engine braking if you drive a combination vehicle consisting of a tractor and a trailer?
Show the correct answer
Correct answer
C. I will put the vehicle in the lowest gear possible, taking into account the rotations of the engine.
Explanation
In the photo, a red tractor with a cab is standing on wet asphalt with a small trailer connected. You get the greatest engine braking effect by engaging the lowest possible gear, taking the engine speed into account - answer C.
Engine braking means that after you take your foot off the accelerator, the resistance of the engine, transferred through the gearbox, slows the wheels down. The lower the gear, the faster the engine turns at a given speed and the harder it brakes. However, you have to watch the engine speed: changing down at too high a speed can rev the engine beyond the permitted range and damage it, and a sudden jerk can make the wheels skid. A higher gear (answer A) weakens engine braking. A pressed clutch (answer B) completely disconnects the engine from the wheels - the combination then rolls freely and speeds up downhill. On a long descent with a heavy trailer, engine braking takes the load off the service brakes and protects them from overheating.
Legal basis: Art. 19 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)