Wot is 'Double Clutching'?

[SheppeyTrio]

This may sound silly to some, but wot is 'Double Clutching'? I've heard it mentioned a few times in films such as Fast and Furious! i.e. 'granny shifting when he should be double clutching!'. Any input on this is welcome and greatful!

[edmo]

I know it's what's done in racing as it's supposed to give a faster and smoother gear change. Can't be that hard tho to master as jonny vegas was doing it round the top gear test track (along with left foot braking I have to add) and he didn't even have a license he was doing it naturally. He nearly gave the stig heart failure and he wanted to get out halfway round. Best lap ever - fink I actually did wet meself

[Ritchy]

its to speed the gearbox up, you did it on older unsynchronised gearboxes, to match the main and lay shaft speeds, theres no reason to do it on a synchro box, its lifting the clutch between gear shifts, so instead of going first, clutch into second, your doing first, clutch,neutral, clutch second, its slower!

[TjP]

Yeah as above.

Some people seem to confuse it with heel-toe for some reason??

[Ritchy]

ive not heard of the heal toe, whats that?

[Phate]

I rev when I change down for smoother gear changes. Yes you don't 'need' to do it but it puts less strain on the box

Heel-toeing is different something which I've got myself in the habit of and find it pretty useful when bombing round a track. You push the brake and throttle pedal at the same time, ties in with revving when changing down - its so you can brake later and harder change into a lower gear at the same time so when you exit the corner you can get the power down faster

[talkingcars]

Originally Posted by ritchyp

its to speed the gearbox up, you did it on older unsynchronised gearboxes, to match the main and lay shaft speeds, theres no reason to do it on a synchro box, its lifting the clutch between gear shifts, so instead of going first, clutch into second, your doing first, clutch,neutral, clutch second, its slower!

You missed the important part, blip the accelerator to increase the engine speed to the gearbox speed in the new gear when changing down.

Originally Posted by wikipedia

Conversely, in order to downshift, engine RPM must be increased while the gearbox is in neutral and the clutch is either engaged or disengaged. This requires the driver to shift into neutral, apply throttle to bring the RPM up to a suitable speed, and finally shift into gear. This operation can be very difficult to master, as it requires the driver to gauge the speed of the vehicle and throttle accurately. Double clutching occurs if the clutch pedal is released while matching engine speeds in neutral and again engaged prior to shifting into the next gear.

http://en.wikipedia.org/wiki/Double_de-clutching

It is great for getting through twisty bits quicker as you can select a lower gear than otherwise so don't loose so much road speed.

There is also info on heal and toe on that link, a less useful alternative in a front wheel drive car, great in rear wheel drive, especially on the loose stuff.

[TjP]

Originally Posted by ritchyp

ive not heard of the heal toe, whats that?

http://www.youtube.com/watch?v=IuoZeuSgEj4

By blipping the throttle when changing down a gear, you match the engine revs to the gearbox revs (if you do it right anyway) so you get a smoother change (and less strain on the gearbox.) Heel-toe is just a skill that lets you do this while braking at the same time. Its a really satisfying skill to learn tbh

[Ritchy]

the heel toe thing i can see being useful ive tried doing that before, the double declutch im never goin to do, how can it be faster to do that than just to go straight into the next gear, unless your wanting to create less stress on the box just like to point out my dads garage specializes in gearboxes:P

[talkingcars]

I was out yesterday evening and drove down a fast bit of country road I know well, as it was quiet I was able to take it quickly, I realised that depending on the bend and weather I need to slow before changing or just drop a gear to hold the road better I use both methods of changing down.