Am I the only one who double clutches?

scardeal wrote: I'm still at a loss as to how holding the clutch in the whole time vs letting it go in the middle and pushing it in again makes any difference whatsoever in wear and tear. If you're rev-matching, isn't THAT what relieves the synchros? Can someone 'splain it to someone without an intimate knowledge of manual transmission internals?

When you double clutch (double declutch), blipping the throttle while the clutch is engaged in Neutral spins up the rotating assembly.

A rev-matched single-clutched downshift and a non rev matched downshift are the same thing as far as the synchros are concerned - the synchro has to do the job of spinning up everything upstream of it. A double-(de)clutched downshift spins the transmission up with the engine.

Bluntly, a rev matched downshift is good for chassis stability, a double-clutched downshift is good for the transmission.

I double clutch/ rev match in my rx-8, otherwise it doesn't like to down shift into 2nd. I think the po was rough on the transmission.

DaewooOfDeath wrote: All of my mechanical sympathy is bleeding!

No sympathy for the devil.

Does non-rev matched shifting really help you get the car rotated? It seems like a slightly less precise equivalent to yanking the hand brake to me.

The handbrake doesn't upset the chassis enough, and the effect's time is different. Different tools for different circumstances.

David S. Wallens wrote: Frank Bullitt double clutches.

Frank Bullitt's sound track double clutched. They dubbed in the sound of an early GT40 for the movie.

pimpm3 wrote: I do and I have for as long as I can remember. Now it just feels wrong if I don't. I have to agree if you heel toe while double clutching it should not effect your braking.

X2

Brought up on British synchros made of hardened cheese, and it is second nature - even do it in my modern sports cars.

In racing, it doesn't slow you - heel and toe and there is no reason to do it early - do it late in the turn just before you need the lower gear and after you're through the serious braking and into set up - trailing braking phase. That often means a shift from 4th to 2nd.

If you are braking hard enough you don't need nor want any additional deceleration - if you do and it works, you weren't braking hard enough. If you were braking hard enough, you'll lock the rears and scare yourself - and maybe those behind you as well.

For those that don't think the ability to double clutch ever comes in handy, I can advise you of one time when my clutch slave grenaded istelf part way through the race on a track with huge elevation changes and very tight turns. Double clutching enabled me to finish the race and not lose time. It didn't impress the pit worker in the pit lane when I was coming in, mind you. He just held his hand up and stepped in front of me, confidently expecting me to stop. Almost nerfed him but stopped in time and shut it off and told him I couldn't move again unless he and his buddies pushed me in. Failed to impress him, apparently but they did push me in to get me out of the way (half the pack was sitting behind me overheating).

A rev-matched single-clutched downshift and a non rev matched downshift are the same thing as far as the synchros are concerned - the synchro has to do the job of spinning up everything upstream of it. A double-(de)clutched downshift spins the transmission up with the engine. Bluntly, a rev matched downshift is good for chassis stability, a double-clutched downshift is good for the transmission.

Best/most concise 2 paragraphs in the thread.

I double clutch rev match downshift on the street constantly. For me, there are two MAIN reasons why i do it:

1. Getting into 1st at any speed (that it will do), any time. I dont have the patience for what 2nd feels like at 10-25 mph in most small-motor cars. But, double clutch rev matched downshifting into 1st completely fixes that. I do it probably a dozen or two times on an average day. If i DIDNT do it and still went to 1st, id have several ruined transmissions right now. I do it on my 337k mile original Insight transmission and though i am feeling it get worse over the last 50k miles, it probably would have munched 1st synchro in a week if i didnt shift that way.

2. Getting into 3rd on the highway. I dont have the patience for what 4th feels like at 65 mph in most cars.. etc etc etc.

I rarely do it to get into 2nd or 4th. I just dont spend a lot of time in the 2nd gear speed range and 5-4 just doesnt need it, imo.

I have double dated, double dribbled and chewed double mint gum twice. As for the double dutch double clutch routine that is reserved for either non synchro or worn synchro transmissions. It was required for the 40s and 50s farm trucks I grew up with. And is semi required for second gear downshifts on my old Saab convert.

David S. Wallens wrote: And Roy Scheider was such a bad-ass that he could double-clutch an automatic: http://youtu.be/9vACWV5sRcY

holy awesomesauce batman: http://www.youtube.com/watch?v=Vf7rqRBIC8g&feature=related (side link)

On my audi I rarely use the clutch. Nice well designed gearbox and synchros. On my MR2 turbo clutch all the time, but never double. Double clutching is for inferior english gearboxes or a transmission with issues.

Since i used to work in a transmission shop i lol a little about this 'double clutching is only for messed up transmissions' thing, because, you know, it's a self-fulfilling prophecy.

I mean, i completely understand not caring on certain things. In my k-cars i never keep one thing put together long enough in terms of miles to care much about durability.

But i do have some rare cars and transmissions and a 300k+ mile DD that i would like NOT to break.. and the good news is it doesnt cost me a damn thing to take synchro wear out of the equation.

I use it only for the very infrequent 2-1 (non-synchronized) downshift in the Sprite and even then it's not seamless.

I do heel-toe downshift in the M3 and Miata nearly always.

For upshifts I use "feel" and "mechanical sensitivity". Particularly in the M3 an upshift has a motion not dissimilar from playing 2 notes with a single stroke on a snare drum - the arm makes a single motion and the wrist divides it into 2 parts: Clutch in, snap it out of gear and ease the effort and speed while feeling it into the next - your fingers and wrist are completing the shift, not the energy stored in the mass of your arm. FEEL IT.

You can do this quite quickly on track. I tell students at HPDEs about this with the suggestion that while shifting not to think you're moving a lever from bottom left to top right, but that you're moving shift forks on shafts and forcing gears apart and back together.

I don't double-clutch. I maybe should, at least getting into 1st gear while moving (like in traffic), because the synchro is getting noisy.

Before synchros, it was a lot more badass to be able to rip off fast shifts.

The sound of a good double-clutch shift is great - the double whoop of the Seven coming in to turn 1 while threshold braking at our local track was awesome.

If you want to get really good at it, try dropping into 1st gear low range in an old Land Rover. No synchro safety net and a big speed change. Heck, that truck likes a quick clutch dip on the 1-2 upshift. No synchro safety net there either.

Nah, I never bother. I don't even really rev match carefully anymore. I throw the revs up higher than needed and dump out with a little trailing throttle. It really doesn't seem to tear up the hardware and it's faster for me to execute.

I know there isn't much lap time to gain in a downshift but I hate to be spending more time in limbo than necessary - if I need to react to something like the car in front over braking or spinning or some slippy juice in the brake zone I want to be in gear so I can use the throttle right away.

Giant Purple Snorklewacker wrote: Nah, I never bother. I don't even really rev match carefully anymore. I throw the revs up higher than needed and dump out with a little trailing throttle. It really doesn't seem to tear up the hardware and it's faster for me to execute. I know there isn't much lap time to gain in a downshift but I hate to be spending more time in limbo than necessary - if I need to react to something like the car in front over braking or spinning or some slippy juice in the brake zone I want to be in gear so I can use the throttle right away.

This is pretty much what I do too. I was afraid to admit it, but if the Wacker does it...

I don't get what you guys are saying about slow double clutching. With a little double clutch rev match that i've been working on, my shifts are faster in my Jeep with an AX15 transmission. If I fight it into gear the "normal" way, it's just a big fight.

In my Astra, I'm just as fast. Maybe it's because my leg is quicker than yours? Then again, my wife does say that I have dancer's legs. Maybe I can just pedal push that fast? I dunno.

I don't think I have every double clutched while down shifting. I simply blip the throttle and hit a lower gear.

Is this the correct process for double clutch down shift?

clutch in, shifter to neutral

clutch out

clutch in, blip throttle, shifter to lower gear

Clutch in

Neutral

throttle

Clutch in

Next gear.

The idea is to re-engage the clutch in neutral to get everything up to speed again before the next gear.

smog7 wrote: I don't think I have every double clutched while down shifting. I simply blip the throttle and hit a lower gear. Is this the correct process for double clutch down shift? clutch in, shifter to neutral clutch out blip throttle clutch in, shifter to lower gear

Fixed.

what are you guys talking about?

By the way, thanks for this thread. I've now found something that distracts me more while driving, because I'm trying to perfect double-clutch downshifts.

And yes, that was sarcasm

However, can't really see the benefit while upshifting. It just feels like it upsets the transmission even more than just hitting the next gear normally.

Plus, I've also been wondering if the extra wear on the throw out bearing (engaging/disengaging the clutch and extra time each shift) negates saving the synchros. Both are a huge pain to fix if they wear out. Yea, you don't have to tear a transmission down to do a throw out bearing, but you still need to crack the trans off the engine...and that's sort of time-consuming, as well as other kinds of annoying.

Oh God don't double clutch on an upshift. Fast and the Furious is the only place that works!

plance1 wrote: what are you guys talking about?

http://www.youtube.com/watch?v=HfTMJlM7Yi8