Double clutching is a driving technique that is usually employed when driving a truck or high performance racecars. But this is a technique that can be used on any car as long as it has a manual transmission.
When driving a manual transmission car, shifting gears is a simple, no-fuss affair. The clutch is depressed then the shifter is moved to go to the next gear (higher or lower), then when the correct gear has been reached the clutch is released, which puts the car back in gear. With a little practice, this becomes one seamless movement every time one switches gears.
With double clutching a third step is added into the process of shifting gears. The clutch is depressed and then the shifter, instead of being placed into the next gear, goes in and stops at neutral when the clutch is released. This is done in order to let the engine slow down or speed up by tapping the gas when downshifting gears. Putting it in neutral will make the transition to the next gear smoother. The driver will then depress the clutch another time and then make the shift to the proper gear before finally releasing clutch. The engine sped will match the gear’s speed in just a split second, so the double clutching process is done in one fluid sequence.
Sychronizers have been equipped on most modern cars. These help in synchronizing the speed of the gearbox to the engine. The synchronizers eliminate the need for double clutching. But there are some vehicles – like large trucks – that have so many gears that synchronizers will not work. Racecars, on the other hand, can get more power out of the engine without a synchronizer.
There are some purists who think that double clutching is still the best way of shifting.