Ok...now I've heard of this, but never really paid much attention to what's behind it all. Never had much stick shift driving before my MCS, being in the big cities and all. Too much of a pain. But this double shift technique keeps coming up here and there on tv or in the movies, and was wondering if anyone could spill the beans on how it's done, what it's all about, the benifits, and possible negative effects of it. I'm guessing it means a faster take off, or pertains to launching a car off the line quicker. How's it done? Maybe a stupid question, but hey. Like they say, when it comes to learning, there's no stupid questions. Thanx in advance for any light shed.
Cheers,

 

double clutching is done in down shifting.In the days before syncromesh it was neccesary to avoid grinding gears while downshifting.It involves putting the clutch in, shifting from the gear you're in to neutral,letting the clutch out in neutral and reving the engine to as close to the rpm's of the next gear down as you can get,putting the clutch in again and shifting to that next gear down and letting the cluch out again (all done as fast as you can do it).with the mini, it can be done to avoid the lurch of just plain down shifting,but again, the faster you can accomplish it ,the better.Sometimes refered to as heel/toe also. Hope this helps.

 

That's a pretty good description. It's like learning to type...a real pain til you aquire muscle memory But soooo worth learning I learned it while driving Semi's in my past life.

So what's with the sound effects when Steve McQueens double blipps the throttle while shifting in the
movie "Bullet"? I could never figure out what he was doing

 

aka (in the UK) as "de-clutching"

Nice explanation, Holden. At the risk of being pedantic (my daughter's favorite vocabulary word ), let me explain a little more about heel-toeing...

"Heel-toe" specifically refers to working the brake pedal and the gas pedal simultaneously with your right foot. You press on the brake with your right foot and then twist your ankle around to blip the gas pedal and increase the revs for the lower gear, while you continue to apply pressure to the brakes. It's kinda like juggling - working three pedals with only two feet. It depends on how the pedals are laid out and the size of your foot whether you use your heel for the gas and your toe for the brake or vice versa. I've been told there are cars where it's easier to do this with the heel on the brake and the toes on the gas, but I've never driven one. (I seem to recall seeing a film of a racing driver doing this a l-o-n-g time ago.)

Note that you can double-clutch without heel-toeing. For instance, when you're downshifting to pass (UK translation="overtake") someone. You certainly won't want to use the brake here, but if you had a car with lousy or no sychros, you'd want to double-clutch. Or shifting to a lower gear as you enter a speed zone. No need to brake here either, but you might double-clutch to make the downshift smoother.

Also note that you can heel-toe without double-clutching. You may be braking and want to get the revs up for the lower gear, but you don't bother shifting to neutral, letting out the clutch, revving, and then shifting into the lower gear. You just push in the clutch, blip the throttle to match the revs, and shift into the next gear. Very smooth downshift, but not a double-clutch.

While we're on the subject, I'll point out that this is a bit of an anchronism, a dying art. Double-clutching and heel-and-toeing used to be very important skills back in the days of crash-boxes and drum brakes. Fifty years ago, you used to have to rely on the engine to help slow you down because the brakes back then were crap. ("Engine braking" it was called.) And you had to be able to double-clutch to get the gears to engage before there was synchromesh. (If you've ever tried to downshift a non-synchro transmission without double-clutching, you'll know why they called them "crash boxes." Yee-ow, what a godawful noise!) Now that we have very good synchromesh (on all forward gears and reverse, even!)* and fade-resistant disc brakes, all this heel-and-toe, double-clutching, and engine braking isn't nearly as important.

As a very good (and honest!) mechanic pointed out to me once, brakes are a lot cheaper to replace than clutches and synchros. There's no reason under normal circumstances to use engine braking.

Unless you're trying to impress someone. And even then, they probably won't know what you're doing. Or if they do know what you're doing, they'll know you're trying to impress them. And they won't be impressed.

* Oh, my god, I just realized something - the MINI that I have on order is going to be my very first manual transmission car with synchro on all gears!. How cool is that!

 

Great explanation but why do you have to go and discourage this lost art by implying that people who practice this technique are showoffs? The point of heel and toe proceedure is to match engine/driveline speed and that's good for the clutch/gearbox/engine. Plus its good clean entertainment with a 6 speed. Hell, I heel/toe out in the boonies just to impress the trees

 

Whoa....thanx for the detailed lesson there all. That helps a lot. I knew about heel and toe, but the whole double clutch thing threw me.
Cheers,

 

Busted!

Why do I double-clutch? Because I can!

 

Actually the term double-clutch came from the time before synchro-mesh gearboxes and the technique req'd to successfully up-shift w/o grinding the gears. See this link....

http://www.cruzers.com/~twakeman/LR/FAQ_clutch.htm


and this one.......

http://www.urs4.com/technical/miscellaneous/Igor.html

 

My wife asked why there is only one clutch pedal....

 

That's true - you can double clutch on upshifts. But you don't really have to. You can simply push in the clutch, wait a sec for the engine and gears to spin down, and then shift. That's not an option when down-shifting.

 

Hee hee! My 1972 Fiat 128 Wagon didn't have synchromesh for first gear, and when first gear went out when I was in the mountains behind Santa Barbara, CA....it was only the most incredible luck that had me not have to stop at a single red light! THAT'S RIGHT! I drove more than 90 miles home to Venice Beach without having to come to a complete stop! HA HA HA! It's a famous story in my family!

As far as heel-toe shifting goes, due to my physical limitations, I am unable to execute such moves......DANG! Sounds like so much fun!

Clover

 

This was in the days before synchros. Try driving an old 30's or 40's farm truck with no synchros. You had to double-clutch to up-shift thru the gears.

 

Lombardstreet is right on the money here. The ONLY reason for letting up the clutch while the car is in neutral as you are in the middle of your shift is to stop some cogs spinning in the transmission that need to mesh. The invention of synchromesh gears has rendered this obsolete for 99% of all cars.

The ONLY modern car that may need to double clutch these days is one where the synchro gears are worn. A rapid shift on a worn synchro will cause the gears to crunch. This can be prevented by a slower shift or a double clutch.

As for the stuff you see on the likes of 2fast 2furious, it is fair to say that hitting a NOS button doesn't make the scenery go fuzzy either

 

Well, ScottinBend is right, too. I remember driving a friend's '32 Ford Model A. (I think that's what it was - that was almost 40 years ago!) No synchros, obviously. If you wanted to drive it in a "spirited" manner (everything's relative), you could speed up your shifts by double-clutching on the way up as well as down. Very funny feeling, sitting up that high, with those high pedals with the long curved shafts that went down through the floorboards - it almost felt like you were doing a jig! But you could also just kinda wait and feel when the gears were getting close and then slip it into the next gear.

This car had another wonderful feature - it was a three-on the floor H pattern with reverse at the upper left corner. You sat up really high, and the stick shift was really long with really long throws. Second was up near the dash - I seem to recall you actually had to lean forward to get it into position - and third was almost against the bench seat. But Bill's car had what apparently was one of the few extras available at the time. I don't remember the name, but it was something like a "necker's shift." Once you were in high, with the gearshift next to the seat, you could lift up on the shift lever, pulling straight up away from the gearbox, and the shift lever would actually disengage itself, and you could flop it up against the dash out of the way. Then your honey could slide over on the seat next to you. Outrageous and totally cool!

Reminds me of something my dad used to say: The problem with bucket seats is not everyone has the same size bucket!