The art of double declutching mostly died out when synchromesh gearboxes were invented, so what place does it have in modern driving? Well, have you ever changed into a lower gear and felt that kick as the engine braking comes in? Double declutching helps to smooth out your gear changes by matching the engine speed to the transmission speed to avoid that mismatch as you engage the clutch.
Double declutching is particularly useful when you need to drop a gear (or two) in order to provide a quick surge of power; for when climbing hills for instance or when you are about to overtake. You can change down and accelerate without that unpleasant jolt you would normally feel.
So how do you do it?
As you press the clutch down and take your foot from the gas, you put the gear lever momentarily into neutral and release the clutch. Next, a quick ‘blip’ of the gas pedal is needed to increase the engine speed. You should then declutch for the second time and engage the required gear. How much extra gas you need to give will depend on whether you are changing down one or two gears.
You need to carry out these movements pretty quickly, too slow and you will lose momentum. Double declutching will need quite a bit of practise; I guarantee that you will get into a bit of a tangle the first few times you try it. For this reason, I would recommend that you practise on an empty road to start with. Give yourself a chance to become competent and confident of the technique before you attempt to do it when overtaking.
Overtaking is probably the time when double declutching comes into its own. When you are following another vehicle and you sense a passing opportunity is about to present itself; changing down to second or third gear to increase your engine speed a few moments before you pull out will give you that all important extra surge of acceleration.
It is also useful for when you are driving up a steep hill. If you find yourself losing momentum, double declutching to a lower gear will give you extra power for the climb. It will also smooth out the transition into a lower gear giving you and your passengers a better driving experience.