Double De-clutching - Idiots guide?
Discussion
Clutch in - blip the throttle to match the revs for the next gear - clutch out.
It makes the whole process smoother - avoids locking the wheels on powerful rear drive cars and makes you feel like some sort of driving genius.
Largely pointless on modern cars but it's nice to be able to do it. Once you have mastered it you can start doing heal and toe - which is equally pointless but actually convinces you that you are a driving genius.
It makes the whole process smoother - avoids locking the wheels on powerful rear drive cars and makes you feel like some sort of driving genius.
Largely pointless on modern cars but it's nice to be able to do it. Once you have mastered it you can start doing heal and toe - which is equally pointless but actually convinces you that you are a driving genius.
Edited by brum on Thursday 7th August 16:09
OllieBirmingham said:
Can anyone explain to me (simply) what this double de-clutching malarkey is all about? Something to do with rev matching when changing down gears?
Double de-clutching is when you take the car out of gear and raise the revs whilst you are in neutral. For example if you are doing 60mph in 4th and you wanted to go into 3rd, you would dip the clutch, push the gears into neutral, release the clutch back up, match the revs to wherever they would be in 3rd at 60, keep them there whilst you dip the clutch back in, select 3rd and let the clutch back out.Some people think it reduces wear and tear on your clutch/syncros.
No you can do a basic rev match with your foot on the clutch so can be different - double de clutching is specifically when you have to be in the neutral with you foot off the clutch when you blip, then you clutch down again to move into the gear you want - it means 2 presses of the clutch pedal, hence the double, one to bring you into neutral and one to go back into the next gear.
Edited by touching cloth on Thursday 7th August 16:24
touching cloth said:
No you can do a basic rev match with your foot on the clutch so can be different - double de clutching is specifically when you have to be in the neutral with you foot off the clutch when you blip, then you clutch down again to move into the gear you want - it means 2 presses of the clutch pedal, hence the double, one to bring you into neutral and one to go back into the next gear.
What he said ^^Edited by touching cloth on Thursday 7th August 16:24
Weird question but I'm sure i remember seeing a lot of classic race and rally cars don't have synchro so are those drivers always double de clutching or can you get away without it. Afraid i'm from the bulletproof, get away with virtually anything gearbox generation although my Dad always mentioned how he had to double de clutch back in the day!
OP - before getting into techniqus of *how* to do this, it's useful to think about *why* and *what* you are doing. The way to visualise it is that there are three separate sections - *roughly* - the engine, the gearbox and the wheels.
There is an interface between each which can be broken and reconnected. (The clutch between the engine and the gearbox, the gear selection between the (front of the) gearbox and the wheels) Where a break and reconnection happens, it is more sympathetic to make sure the components are spinning together with similar torques before engaging or disengaging them.
Most drivers don't manage either interface.
Simple rev matching - getting the engine revs up or down to speed prior to releasing the clutch is managing the first interface -- between the engine and the gearbox. This is a big step forward in sympathy since the shunt that the engine can give the (engaged) gearbox and hence wheels is really big.
DDC is managing the second interface - between the gearbox and the wheels. It's a finer point as
i) the rotational inertia of the gearbox is much smaller than that of the engine
ii) synchro rings help this happen.
There is an interface between each which can be broken and reconnected. (The clutch between the engine and the gearbox, the gear selection between the (front of the) gearbox and the wheels) Where a break and reconnection happens, it is more sympathetic to make sure the components are spinning together with similar torques before engaging or disengaging them.
Most drivers don't manage either interface.
Simple rev matching - getting the engine revs up or down to speed prior to releasing the clutch is managing the first interface -- between the engine and the gearbox. This is a big step forward in sympathy since the shunt that the engine can give the (engaged) gearbox and hence wheels is really big.
DDC is managing the second interface - between the gearbox and the wheels. It's a finer point as
i) the rotational inertia of the gearbox is much smaller than that of the engine
ii) synchro rings help this happen.
Stedman said:
discoman said:
Where I live some of the idiots who talk about double de-clutching think it is simply pressing the clutch in again whilst accelerating to get a little boost 
WHO YOU CALLING AN IDIOT?! Edited by discoman on Friday 8th August 00:46
I have to DDC into 5th as I damaged the 5th gear syncro and it clunks a bit of I dont DDC.
As its been like this for ages I do it naturally and its no slower than changing gear normally.
But as I still have a half working syncro if I dont get it perfect the gear still goes in ok, its just not as smooth.
Although im pretty good at DDCing I dont bother for any other changes as its not needed. My 5th gear syncro only broke as they are weak on these cars anyway and I was (very) clumsy one day selecting 5th instead of 3rd by accident.
As its been like this for ages I do it naturally and its no slower than changing gear normally.
But as I still have a half working syncro if I dont get it perfect the gear still goes in ok, its just not as smooth.
Although im pretty good at DDCing I dont bother for any other changes as its not needed. My 5th gear syncro only broke as they are weak on these cars anyway and I was (very) clumsy one day selecting 5th instead of 3rd by accident.
jammy_basturd said:
If you get the revs right, you can change gear without a clutch, brutal if you get it wrong though! You can do that with any type of gearbox.
This was very common practice amoungst competiton drivers and many ordinary road drivers in the days of only crashboxes. Interestingly, it was these drivers that also developed heel and toe so they could brake and rev the engine to get the thing down a cog or two when needed. - Pretty much the only way you could change down if on a steep decent especially if, as was often the case, engine braking played an important part to avoid cooking the brakes. discoman said:
Where I live some of the idiots who talk about double de-clutching think it is simply pressing the clutch in again whilst accelerating to get a little boost
No, that's cadence clutching!Edited by discoman on Friday 8th August 00:46
IIRC a lot of talk about double de-clutching came about within 'those' circles because of 'The Fast & Furious', where the guy had the piss taken out of him for not doing it on the upshift! Er...
7db said:
OP - before getting into techniqus of *how* to do this, it's useful to think about *why* and *what* you are doing. The way to visualise it is that there are three separate sections - *roughly* - the engine, the gearbox and the wheels.
There is an interface between each which can be broken and reconnected. (The clutch between the engine and the gearbox, the gear selection between the (front of the) gearbox and the wheels) Where a break and reconnection happens, it is more sympathetic to make sure the components are spinning together with similar torques before engaging or disengaging them.
Most drivers don't manage either interface.
Simple rev matching - getting the engine revs up or down to speed prior to releasing the clutch is managing the first interface -- between the engine and the gearbox. This is a big step forward in sympathy since the shunt that the engine can give the (engaged) gearbox and hence wheels is really big.
DDC is managing the second interface - between the gearbox and the wheels. It's a finer point as
i) the rotational inertia of the gearbox is much smaller than that of the engine
ii) synchro rings help this happen.
interesting...There is an interface between each which can be broken and reconnected. (The clutch between the engine and the gearbox, the gear selection between the (front of the) gearbox and the wheels) Where a break and reconnection happens, it is more sympathetic to make sure the components are spinning together with similar torques before engaging or disengaging them.
Most drivers don't manage either interface.
Simple rev matching - getting the engine revs up or down to speed prior to releasing the clutch is managing the first interface -- between the engine and the gearbox. This is a big step forward in sympathy since the shunt that the engine can give the (engaged) gearbox and hence wheels is really big.
DDC is managing the second interface - between the gearbox and the wheels. It's a finer point as
i) the rotational inertia of the gearbox is much smaller than that of the engine
ii) synchro rings help this happen.
it would appear that im able to partly do the first interface..i had no idea what DDC was before reading this post, however I have got into the habit of blipping the throttle when shifting down a gear (whilst the clutch is engaged). I found that it greatly smoothed out changes in my old car (a 350z) and ive continued to do it by habit in my current car (a focus ST), as it still offers a little more degree of smoothness.
heel and toeing i know i cant do as ive tried and tried in vain. i think i would be correct in saying that if one could manage this then interface 2 you speak of would occur as you are slowing the car down and matching engine speed thus linking the "3 sections" of the car you speak of?
ETA that ive just read the heel and toeing thread however.. i must confess that i find the pedals on my ST too far apart to manage it
Edited by red_zed on Tuesday 12th August 13:43
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