Double-declutching...

[TomM]

Can someone explain the concept behind this? I've asked loads of people, and have recieved several different explainations!

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Driving a Citroen AX 1.4D... mmm mmm!

[Sal]

The way i understand it , to change gear you would have to :

clutch in and take it out of gear.
in neutral rev the engine to the appropriate speeed and then put the clutch back in and select the next gear.

might be a load of old bollards but you never know, I am sometimes right on the button ???

Sal

[davidra]

To double - declutch:

Press clutch down
Put gearbox into neutral
Let clutch up
Pause
Put clutch down
Put gearbox into new gear
Let clutch up

You should feel that this is smoother than normal changing i.e. less notchy. I think its because you allow more time for the synchro to adjust and when you're engaging gear the speeds are more similar. someone correct me?!

I don't think it really has any benefit any more, unless your gearbox is wrecked.

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stock 200SX S13, dark blue
Broken wipers, leaks brake fluid. Clutch on way out, gearbox notchy. Some rust / shoddy welding.
Smelly tree nasal enhancement.

[Sal]

I thought this was a technique used on old vehicles that did not have a synchro so you could not change gear without doing it, but in vehicles with the synchro its not needed ?

Sal

[AshT_200]

Straight cut gears.


Originally posted by Sal:
I thought this was a technique used on old vehicles that did not have a synchro so you could not change gear without doing it, but in vehicles with the synchro its not needed ?

Sal

[Chris_Lacey]

How in gods name could that be done quickly?! Must add seconds to a 1/4 mile time...

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'92 S13 200SX Silver Blue Metallic.
7 Spoke Nissan Alloys, bonus rusted tailgate for weight reduction :-)

[Billy]

It's about matching engine and gearbox speeds. It takes longer to explain than to do, and it won't affect your 0-60 times, 'cause you only do it on the way down the box. When changing up, the engine revs drop to gearbox speed anyway (unless you go in for full throttle shifts).

It's a useful technique for when your syncro's goosed, and matching engine/gearbox speeds is useful when your clutch hydraulics run dry/cable snaps, but otherwise it just sounds good. (The automatic throttle blip on downshift is the best part of the Alfa selespeed system!)

Of course, (takes life in hands here!) you'll be needing a clutch pedal.....

[Sal]

careful billy !

[Chris_Lacey]

I'm okay then :-) Not that I would post a message like "2 pedals good, 3 pedals better :-) "

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'92 S13 200SX Silver Blue Metallic.
7 Spoke Nissan Alloys, bonus rusted tailgate for weight reduction :-)

[docwra]

try practicing changing gear without using the clutch - its much easier on the way down than up - you should be able to feel where the change is
Unfortunately I dont have the bottle to do this while travelling quickly - more a party trick than anything else (although it came in handy when the clutch cable on my last motor went)


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92 200SX, grey
K+N 57i (Im ready for max power now!!)
Bit of ICE, cant be arsed to take the dash off to put more in
Manual, for I have the stick in the middle of my car and in the middle of my legs
Never refuse a challenge!!
gentlemen prefer blondes ......

[TomM]

Originally posted by docwra:
try practicing changing gear without using the clutch

I used to be able to do this all the time (in my AX http://300zx.co.uk/200sx/ubb/smile.gif ) but now the gearbox has gone really ****e, so I just have to nurse it... http://300zx.co.uk/200sx/ubb/frown.gif

THinking about it, is the effect of double-declutching any different from just doing a long clutch-in, with a slow gear-change?

[Jez]

Originally posted by Sal:
I thought this was a technique used on old vehicles that did not have a synchro so you could not change gear without doing it, but in vehicles with the synchro its not needed ?

Sal

Sal's right - double de-clutching is only required on really old 'boxes without synchromesh. Its not worth doing it on modern gearboxes - it will cost you a lot of time.

Theres also another technique call heal and toeing which Im sure you've all heard of so I wont bore you with the details

[TomM]

Originally posted by Jez:
Theres also another technique call heal and toeing which Im sure you've all heard of so I wont bore you with the details

A ha! That was the other technique I was wondering about... isn't it something to do with keeping the revs up whilst down-shifting (or am I way way out?)

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Driving a Citroen AX 1.4D... mmm mmm!

[Paul_Ralph]

helped 0-60 times on the ol' Bedford 4 tonne !!!! luverly diesel

[turbo pete]

Do a search on this.

I posted a big reply as did many others tothis very same question.

Turbo pete

[davidra]

Concluding note:

(IMHO) don't try changing gear without the clutch! I've tried it on old bangers but it doesn't do the gearbox any good. The clutch allows the gearbox / engine combo to adjust speed gradually, whereas without it the 'straight cut cogs' will try to bind immediately (and could break).

(Also IMHO) Double - declutching may make things easier than normal gearchanges, but maybe just because it takes you so long...

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stock 200SX S13, dark blue
Broken wipers, leaks brake fluid. Clutch on way out, gearbox notchy. Some rust / shoddy welding.
Smelly tree nasal enhancement.

[andyf]

Quick note: Heel + Toe / Double Declutching done mainly by heroic race drivers who wish to have the ultimate weight balance control of their cars, as downshifting without getting the revs right when already braking like a lunatic can cause the wheels to lock, which is less than perfect (but makes for great TV, especially if it's the touring cars)

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Site Admin of Silvia-S13.Net (http://www.silvia-s13.net) and BB (http://www.silvia-s13.net/board)
Big Garrett powered S13

[Sideways Stanley]

How can you down shift quickly without heel & toeing?!?
from experience I've found that not doing it properly leads to character building shift lock (esp on track days!).
but mabybe it because I've been doing it for so long, I'd have to think to not doing it;-)


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'90 grey S13
plus tweaks

[J595HAS]

Have I logged into eddiestobart.co.uk by accident ????