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Originally Posted by petrohead Im afraid you got it wrong malcolm! Let me explain how.
Double clutching was once a required technique. It was used to sync the engine and transmission speed. In older cars without double clutching you were unable to shift (you even had to double clutch to up shift). However, in new transmissions synchromesh gears do most of that work. While the synchromesh gears reduce the need for double clutching, they don’t handle the large changes in speed that go with down shifts very well. Double clutching makes the downshifts smoother and saves wear on the transmission by reducing the amount of work done by the synchromesh units. So go out and practice a double clutch down shift (in a safe place), it’ll save you precious money on your transmission.
The hardest part is figuring out how much to raise the engine revs. It depends on how fast you’re going and your transmission’s gearing. Got to get that by practice.
I caught up with a video in Youtube and practiced double clutching, its fun when you really go out for a fast ride  |
I have been riding / driving for about 3 decades now. I have seen them all, the constant mesh, the partly syncromesh, the fully syncromesh gear boxes, the 'semi-automatic' (no clutch) boxes, automatics (no gear lever / clutch - UGH!) to the latest 'DSG'.
One thing has not changed over the years - in manual gearboxes, you need to use the clutch in different ways to shift up/down depending on the conditions (vehicle condition, load, road speed, engine speed etc.).
Clutching fell into four broad categories:
1. Normal or single clutch (as one does when starting from stop) - when one wanted to shift up/down one depressed the clutch and shifted from gear to gear (often without halting in neutral).
2. "No clutch" shifts - experienced drivers who knew their vehicles intimately did not depress the clutch at all when shifting up, relying merely on their ears and feel (feedback via the gear lever) to ease the vehicle into one gear from another. Incidentally bus drivers are past masters at this courtesy the light vehicle load and their long hours behind the wheel. Drag racers at signals too used this to move up and down the gears quickly. WARNING - If you do not get it right, you can bust your box or worse, have a bad spill! Downshifting without using the clutch was particularly tricky as one had to match and time the use of brake pedal and gear shift perfectly.
3. Partial clutch - a neat compromise between the first two where the driver depresses the clutch partly to provide a cushion to accomodate any 'margin of error' in matching the engine speeds.
4. Double de-clutching was required only when there was a sticky shift on the offing i.e. the gear lever kinda balked at the thought of moving into another gear, this the driver felt as a resistance in his palm when trying to shift. Double de-clutching was also the method of choice when one had to ensure a fool proof shift eg. on a ghat road or when overtaking at high speed (with a full load) with heavy on coming traffic.
I have used every one of these techniques on the vehicles I have owned - Ambassodar, Padmini, Herald, Lambretta, Jawa, Suzuki-Supra, 118NE, Opel Corsa, I however lay off the no-clutch technique on my Laura as there is no need and, the box is too expensive to replace!
