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Whats the point of double clutching??

Shadowness

Shadowness

Well-Known Member
Joined
Jun 20, 2005
Messages
1,111
Location
Midlands, UK
Car(s)
Caged Clio 182 Track Car
Hi, my first post of FinalGear! Frequently visit here, the site's awesome, keep up the good work!
Anyway, my question: Why double clutch/declutch? Here's a good description of how it's done:
You do "double declutching" on the downshift:

lift off => depress the clutch => switch into neutral => release the clutch => [blip the throttle, increasing rpm in order to match the higher rpm of the secondary shaft in the gearbox needed for the bigger DIA lower gear] => depress the clutch => switch into a lower gear => release the clutch => step on the gas.
Click to expand...

My question is why go into neutral, whats the point, surely that takes loads of time and thinking to do!? Why cant u just blip the throttle when the clutch is in, why go to neutral?
thanks (sorry if this is a stupid question)
 
when you blip it with the clutch in, you rev up the engine, but not the gearbox caus your clutch is open, while in neutral, the clutch is closed and the gearbox spins as well, but without traversing it to the wheels

and the goal of clutchless shifting is that the gearbox shouldn't be having to much stress, that everything goes smooth, so you have to let go in neutral before it's effective, it works without as well, but doesn't change anything
 
The difference is that in heel-toe downshifting you also use the brake pedal.
You use double declutch if you just want to change down a gear and heel-toe downshifting if you really want to slow down like when coming to a corner.

Anyone correct this if it's wrong.
 
that's something completely different

heel-toe downshifting is when entering a corner, and you tip your brakes, you loose grip for a split second and the car goes a little sideways which gives better turn-in
 
you shouldn't be using it anymore with the invention of syncro rings it became a moot point

TF
 
as TF said... double-clutching is used on straight-cut gearboxes that do not have syncros where rev-matching is very important.... on modern manuals, its not so ;)
 
The importance of both techniques today is only in motorsports and sporty driving.
 
healtoe is for sporty rev matching and quick smooth shifts double clutching take to long i would never double clutch when i am driving fast

TF
 
The_Finn said:
you shouldn't be using it anymore with the invention of syncro rings it became a moot point

TF
Click to expand...
Unless you want to reduce synchro wear, cause they do wear out and then it's a pain in the ass to change gear. I used to double clutch my jeep cause the synchros were junk and it was easier and faster to double clutch. I do it in my saab cause it cause it feels much nicer when you do it right.
 
Raven18940 said:
The_Finn said:
you shouldn't be using it anymore with the invention of syncro rings it became a moot point

TF
Click to expand...
Unless you want to reduce synchro wear, cause they do wear out and then it's a pain in the ass to change gear. I used to double clutch my jeep cause the synchros were junk and it was easier and faster to double clutch. I do it in my saab cause it cause it feels much nicer when you do it right.
Click to expand...

And when you stuff it up.... WRRRRRRRrrrrrrrrrrrhhhhhhhhhhh.... KKKKXXXxxxxxxxxxxxxttttt.....

haha
 
bone said:
heel-toe downshifting is when entering a corner, and you tip your brakes, you loose grip for a split second and the car goes a little sideways which gives better turn-in
Click to expand...

What is this rubbish? Perhaps in the drifting or rally scene where the driver wants the car to go sideways.

IMO most, if not all, road race drivers would not want to go sideways, placing undue wear on the tyres and loosing grip in the process. Point and shoot would be their goal i'd suspect.

All heal-toe-ing is doing is matching engine revs with revs of the gear you wish to select while breaking. Change down without matching revs and if you do it quickly, you'll most like cause a compression lockup of the wheels.

Besides this point you SHOULD NOT be braking/changing gears mid corner anyway. All the braking/gear changing should be all worked out well before turn-in.

The Finn is on the money, it is not needed in anything semi recent and is MUCH SLOWER.

There are always exceptions, older trucks and crusty old vehicles/gearboxes/clutches may require it to engage correctly, but you are hardly try to change gears quickly in any of these things anyway.
 
dunno, but if i watch BMI, they do it all the time when entering a corner
 
freerider said:
Double clutching was used to minimalize the wear on the tranny. Nowadays it isn't done anymore. It's also slower then changing gears normal, so I don't think they use it anymore in racing.
here are some vids explaining it all. Look at instructional videos.
Click to expand...

I got all excited for a moment, but those video links don't seem to do a great deal, when did you check them last?
 
It was used in cars that did not have synchronised gears.
Now, roadcars have sychronised gears that match the gear speed with engine speed.

You usually only do it in a downshift. In an upshift, the revs are perfectly matched when you time your shift right.

I have a lightweight car with a beefy gearbox. It has 200k miles on it so I double clutch to keep the downshifts smooth and extend the gearbox life.
 
Shadowness said:
yeh those video links do nothing, anyone else know where we can see these techniques on video?
Click to expand...

I'll upload them later. I didn't check if the downloads still work. But now I have to study first (exams)
 
Shadowness said:
cool, thanks very much. I know how it is, i got exams too at the mo :( :thumbsdown:
Click to expand...

I just had my last one today :D .
I'm sorry, but I can't upload it. Upload speed is stuck at 1kb/s. Would take me days to upload it (144MB IIRC).
But it's actually nothing special. Just some guy in an m5 telling you everything and then show it. (dbl clutching, seeting position, gentle launch, hard launch,...). It's nice if you're really interested, but it's not full of action.

Greetz Johan
 
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