Why is double clutching used

Read on to find out more about how double-clutching works and in which scenarios double-clutching proves the most useful. While regular shifting describes the process of methodically sequencing up or down through the gears, other techniques exist for changing gears in certain situations, which can speed up or otherwise improve changing gears for more speed. One of these techniques is double-clutching, which engages the clutch twice in a row while changing gears.

It isn't used to shift up because the process involves matching the engine speed with the desired gear as a goal. For upshifts, the process of pressing the clutch and lifting off the accelerator drops the engine's speed sufficiently, followed by continued acceleration with a nearly unchanged transmission speed.

While the wheels are still traveling nearly as fast as before, the reduction of engine speed matches the wheels to the gear desired to engage. For downshifts, the speed of your engine needs to be higher than that of the wheels and transmission. This is when double-clutching proves ideal , instead of immediately shifting into the next gear, drivers would put it in neutral and release the clutch.

Then tap the accelerator to increase both the engine and clutch speed , followed by the usual clutch press and gear selection.

When practiced properly, the whole technique only takes about half a second. Most modern cars are equipped with devices called synchronizers that help match the speed of the transmission with that of the engine, which effectively eliminates the need for double clutching.

Some large trucks, however, have so many gears that synchronizers are inefficient; in addition, race-car drivers can get more power out of the engine without them. Double clutching can aid high-performance driving because it can give the driver more control of a vehicle as he or she slows to go through a turn.

Without the maneuver, a vehicle has a tendency to fishtail when going around a sharp turn and decelerating from a high speed, because jamming on the brakes tends to abruptly throw the weight of the vehicle forward. By downshifting, a driver can also slow the vehicle with the engine, taking some pressure off the brakes. This can be particularly important for heavily laden commercial trucks descending steep downgrades, where burning out brakes can create a serious hazard.

Sometimes the driver of a regular manual transmission car may want to make use of double clutching. Downshifting, shifting into a lower gear, has advantages in slippery conditions; rather than brake and skid, a car with a manual transmission can make use of the engine to slow down, making a skid less likely.

In lower gears, the engine will spin fast relative to the transmission output shaft. In high gears, the transmission output shaft will spin quickly relative to the engine. Double clutching, although slightly time consuming, eases gear selection when an extended delay or variance exists between engine and transmission speeds, and delays the wearing on the synchronizers, which are just brass cone clutches themselves, and wear out slightly a little bit every time they are used to equalize the transmission revs with the output revs.

The first declutching is simply to make taking the transmission out of gear easier. In fact, considering it would have taken him longer to shift into the next gear — since he would have had to push the clutch in twice — he probably would have lost the race anyway.

What is double clutching?