Braking with the gear box
To brake with the gear box means to pass from gear to gear and make the most of the engine’s slowing down possibility at the maximum torque zone. It’s important to know this for light and, especially, for heavy vehicles.
Firstly, it’s necessary to identify which are the speeds that the vehicle reaches at each gear when the engine is working at its torque (for this, check the user manual). We will exemplify this with a vehicle with 5 gears, like the VW GOL 1.8, with its maximum torque at 2750rpm. The graph below shows the hypothetic speeds that the manufacturer says it can reach.
(Illustrative values. They vary with vehicle’s type and model)
Let’s suppose that we are driving in gear 4, with the engine running at 2750rpm. The speed is of 84km/h approximately. The first braking action is to lift the foot of the accelerator pedal, thus we feel that the engine slows down the vehicle. When the speed goes down to 56km/h, we get close to the advisable speed for 3rd gear. So, we push the clutch brake, change from 4th to 3rd, and release gently the pedal. We’ll see that the engine places itself in a value near 2750rpm, its maximum braking power. The vehicle’s speed will continue to slow down and when it reaches 37km/h, we change from 3rd to 2nd.
This procedure is done in a descent way for each change. It’s not necessary to follow the changes order, e.g. we can pass from 5th to 3rd, but only when the engine is on the right regime for that change. If not, we damage the clutch or the engine.
Driving Techniques