[new_sti_lvr]

Ever driven a manual trans without synchro's? SM465 is an old cast GM transmission used in their 3/4 and 1 ton trucks during the 70's mostly (although used before and after for a bit as well). In any event, double clutching is a way of life with those, its certainly easier on todays synchro's as well because there work is for the most part elminiated. Driving an SM465 and not having the gears grind between 2nd and 3rd (there's 4 gears, but the first is a granny that you never use unless offroad) is a challenge. Give it a try sometime, its certainly an experience compared with the wonderful transmissions we have now a days. I've got an old '78 1 ton to play around in and pull the car trailer.

[pgetchell]

Originally Posted by 4MLA1FN

i don't think people need to double-clutch anymore. we've got synchros that make changing gears effortless. i guess double-clutching would make life easier on the synchros, in theory.

that is what I have heard, you really do not need to, you can simply match the revs and let the synchros do the trick. makes it quicker than the clutch-neutral-unclutch-rev-clutch...or whatever.

But, on the other hand, double clutching may theoretically be easier on the tranny's innards.

[SnowbordrWRX]

I split off the F&F idiocies discussion into Off-Topic if you were looking for it. Splits oughta have shadows...

[Goose]

As stated, double clutching is essential when the synchro is crap or not there at all... I drove a escort cosworth in Ireland that had the worst synchro I've ever seen... (What do you expect from a ford) You couldn't down gear without double clutching...

[CloNeGTS]

Double clutching IS essential in some cars, but it does serve a very real purpose in today's cars as well.

Now, this doesn't mean you need to double clutch going UP the gears as stated in FnF and in that damn RSX-S commercial. All that does is make lots of cool engine noise.

Down shifting is a different story. You save your synchros a great deal of wear by double clutching. This isn't the same as rev matching. Double clutching gets all of the gears in the transmission up to speed so that when you do rev match as you shift into gear, everything meshes perfectly. Otherwise, the synchro is responsible for spinning up your entire transmission (not just the gear you are going into).

This pic should help.



If you are in gear, with the clutch disengaged, all of the gears in the transmission are spinning at the speed of the wheels. This is why you can't get into reverse cleanly when rolling. With the clutch disengaged and not in gear, the gears are free to spin down. If you are out of gear with the clutch engaged, the gears will spin at the speed of the engine. This is where double clutching is great. Spin those gears up, get back into the right gear without using the synchro, and then match the engine to the tranny's speed.

Ahhh.....there is nothing like a perfectly executed double clutch downshift.

Oh yeah, and when you are good at it, it doesn't take but an instant longer...but you should be slowing down if you are down shifting anyway, so why does it matter? You can keep braking.

[CloNeGTS]

Oh....and as for the smoothness of shifting a la rev matching, double clutching or neither.....it is essential in most forms of racing, especially autox with street cars, that you can downshift without effecting the balance of the car AT ALL. Rev matching is the first step to getting this. When you can rev match and you can continue to slow down perfectly linearly as if you weren't in gear at all and just using the brakes, you've got it. Once at that point, now work to get double clutching just as smooth. I double clutch every day on the street...it takes a while to get smooth at, but it is very easy to do with practice.

[rx4fun]

You can blip the throttle to match revs with the DBW on the STi.