Who knows what double clutching is ? The correct method od double clutching is as below and not the misconception of firing your foot onto the clutch once a gear ahs been engaged whilst still accelerating to get the infamous extra revs! BTW (Vin Diesel in the fast and Furious says "granny shifting, not double clutching like you should..."). .
First: Dont watch the fast and the furious and think it has anything to do with cars. Anything they say about cars in that movie should be assumed faulty until proven correct.
Now, double clutching is done for downshifts only. You NEVER double clutch when you upshift. It makes no sense.
Proper double clutch procedure (downshifting!):
Push clutch in.
Move shifter to neutral.
Rev engine to a slightly higher rpm than what the engine will be in the lower gear.
Push clutch back in
Move shifter to lower gear.
So what does it do? It revs the tranny input shaft to the rpm where it will be in the lower gear. That means that when you attempt to move the shifter to the lower gear everything is already spinning at the proper rpm. Done right this pretty much eliminates wear on the synchronizers.
Yes, this was mandatory on old trannies that were not synchronized. It is still useful for downshifting multiple gears. For instance, I will often coast down in high gear to maybe 1200-1400 rpm. Then I need to accelerate and want 2nd gear. A quick double clutch will make 2nd just fall in place with no effort on the shifter lever.
I find it even more useful going into 1st gear while rolling. In many cars it is very difficult to get 1st gear while rolling. A double clutch will make the most stubborn tranny go into 1st.
Here endith the lesson.................works a treat by the way through the forest stages............