The new FAQ on the front page for double clutching is great. I have never seen it explained so well. So the past few days I have been trying it and I have noticed something and need someone to tell me where I am wrong. I don't notice a difference between double clutching and putting the clutch in and reving to the appropriate RPM on the way to my downshift gear. Both feel the exact same to me as far as the re-entry into the gear. Is this normal...is there that big of a differnce between double clutching and the technique I am used to using??? I assume double clutching saves the syncro's more or something?

Thanks!

 

Anyone??? TTT

 

ok i tried the same thing and i notice something....correct me on this one..aren't syncros designed to match your layshaft speed with your gears? anyway, driving at 40 MPH i pushed the clutch in while in higher gear.....and went into second like i would....but not going into the gear all the way...half way it stopped me and i kept slight pressure on it til seconds later it went in smoothly. That's when i knew the syncro did it's job....then revved matched it and it was smooth....when i did that i could hear the sound of the syncro speeding up....a high pitch whistling sound...you know like when you slow down to stop....and you try to put it in first gear and hear that sound? im pretty sure that's the syncro working. So i dont think there's a need to double clutch unless you want to downshift quickly and you do it the old way. But i think it's just awkward as heck trying to do that compare to just letting the syncro matches the speed for you. Unless you're so used to it.

 

If you rev the engine with the clutch depressed and match the engine speed to your road speed then when you release the clutch in the new (lower) gear you will have a smooth transition without a jerk. BUT that is not a double clutch. The advantage of the true double clutch is that by reving the engine with the clutch pedal out you match the speed of the xmission input shaft to the speed of the output shaft, thus saving the wear and tear on your synchros. The pedal must be out because with the pedal depressed the engine is not connected to the xmission input shaft.

In fact, when you do it right you can feel the gear lever just slip in SO smoothly w/o any resistance. Also if you learn how to double clutch right you can shift WITHOUT USING THE CLUTCH AT ALL w/o hurting the xmission. In this case you are not actually "double clutching" (you don't use the clutch at all). Instead you pull it out of gear, rev the engine to match speeds (holding the proper revs) and then slip it into the lower gear. I have driven many a car this way when I broke a clutch cable or lost a clutch slave cylinder. If you have to stop you just slip it in neutral and turn off the engine. Then put it in first and when ready to go hit the starter and lurch away and then shift up and down as needed.

 

Other than added wear and tear on the throwout bearing, the clutch actuation points and your leg, there is no benefit. The syncro's do the work all you have to do is match rev's for clean down shifting.

One other thing clutchless downshifting is not very beneficial to longevity of the drivetrain. The clutch being the first problem. I don't advise doing this for any reason. With the short throw of the gear lever and the close ratio gear box there's no need. Please don't confuse the use in F-1 racing. The clutch is only used at the start because the transmission works like a semi automatic.

 

Just do it ... Definitely sounds professional outside if you have your exhaust changed, or at high revs it does sound different to the others. Not many know how to do that, so it's a good skill to learn. Nothing bad for the car, so why not?

 

Bottom line is that double-clutching isn't needed, but I think that to get a little more performance out of the car, it helps. I feel that I can downshift faster when double-clutching than not. And the motion from neutral into the what ever gear I'm going into is quicker. I don't have to wait for the syncros to do their job. Sometimes there is hesitation if the shaft speeds aren't close enough. But with double-clutching done right, there is absolutely no hesitation. Plus ripping through all the gears from 6th to second for a slow corner sounds awesome.

 

Double clutching helps in the following ways:
1) it saves your synchros the hard work of having to match potentially 3000 revs of difference going from 1-2.
2) it slows down your shift fractionally enough to give you a well timed rev match.

In any event, DO NOT shift without the clutch or rush the shift unless you want a transmission that will grind even when you don't rush it.

 

Cool FAQ, just went and spent an hour practicing.