baH.. i just explained what double clutching was at the beginning of the thread.. let me show you guys a few scenarios

first scenario, you're approaching a turn going about 40mph and you're in 4th gear.. you want to down shift into second gear so you can accelerate through the turn. this is when you double clutch: push the clutch down, shift into neutral, release clutch, rev engine to high RPM, push clutch down, shift into second, accelerate through turn... you should notice a smooth transition from 4th to 2nd.. this is good for your tranny

second scenario, if you didn't use double clutching: approaching turn going 40mph in 4th gear, you push the clutch down, shift from 4th to 2nd, release clutch, the car jerks forward like a ***** and it's bad for your tranny and your RPMs just jumped about 4k all of a sudden.. this is what happens when you downshift and don't double clutch

end of discussion.