How do you double declutch?
Discussion
Double declutching was only really needed in older gearboxes where you had to help equal the speed of the gear meshes so that when you dropped the clutch you didnt knacker the box.
Basically all you are doing is dipping the clutch twice, first time to take out of gear, second too put it into the new gear, with a big rev in between.
You time the rev to start as you start the first clutch dip, and then to be on the gas as new gear is selected after second dip.
For the same sound effect just rev her between changes on the downshift, this can also help stopping you losing the tail because your revs are high so when you drop down a gear all the torque isnt being put straight to the rear wheels, there will be guys with better explanations on here I am sure but that gives you something to go on with!!! cheers
Basically all you are doing is dipping the clutch twice, first time to take out of gear, second too put it into the new gear, with a big rev in between.
You time the rev to start as you start the first clutch dip, and then to be on the gas as new gear is selected after second dip.
For the same sound effect just rev her between changes on the downshift, this can also help stopping you losing the tail because your revs are high so when you drop down a gear all the torque isnt being put straight to the rear wheels, there will be guys with better explanations on here I am sure but that gives you something to go on with!!! cheers
Its usually best to match engine revs and road speed on a down change by blipping the throttle (heel and toe takes this one step further), some cars with flappy paddle changes blip the throttle automatically on a down change.
Matching the revs reduces stress on the drive train, and if you have a lot of power and a light rear wheel drive car you can unstick the rear wheels if you dont match the revs, a bit like pulling on the handbrake, with similar consequences on the wet or or corners
Matching the revs reduces stress on the drive train, and if you have a lot of power and a light rear wheel drive car you can unstick the rear wheels if you dont match the revs, a bit like pulling on the handbrake, with similar consequences on the wet or or corners
Foot on clutch and gear lever to neutral, off clutch and blip throttle, on clutch again and into next gear.
Aim is to match road / engine speed for downshift and also to spin up the gear so that you are not meshing an already moving cog into the slower or stationary next gear (the latter is what sychromesh does for you in modern gearboxes but if you get it right even on a modern box it will make for a smoother change as no loading on the sychro)
A perfect change will feel really smooth, fast and the rev counter should show rise in revs as you blip in neutral and then needle stays there as you select the lower gear, too mcuh or little of a blip in neutral will see a rev change or too slow will see a falling off of revs.
On old boxes you also double declutch on the upshift but there is no need to blip the throttle as you want the revs to fall in the higher gear not rise.
Aim is to match road / engine speed for downshift and also to spin up the gear so that you are not meshing an already moving cog into the slower or stationary next gear (the latter is what sychromesh does for you in modern gearboxes but if you get it right even on a modern box it will make for a smoother change as no loading on the sychro)
A perfect change will feel really smooth, fast and the rev counter should show rise in revs as you blip in neutral and then needle stays there as you select the lower gear, too mcuh or little of a blip in neutral will see a rev change or too slow will see a falling off of revs.
On old boxes you also double declutch on the upshift but there is no need to blip the throttle as you want the revs to fall in the higher gear not rise.
After considerable criticism of double-declutching from various vested interests, when I was in charge of a police driving school I did some research on the matter. Whilst it was demanded in Roadcraft, if it was pointless doing it, I saw no point in teaching it. After all syncromesh gearboxes had come a long way since the book had been originally written.
The four things that a police driving school teaches are: System (the Roadcraft model), Safety, Speed and Smoothness.
We found no driver capable of being as smooth without double-declutching as with it, but some were able to get quite close. Not really conclusive evidence either way.
Then one of my instructors had the brilliant idea to contact all the gearbox manufacturers he could think of in this country and a number in the USA to canvas their opinions. One failed to reply. The rest were universal in their conclusion that double-declutching cut down wear on the gearbox and some had research (not shared) to prove it. Others mentioned that they would assume that the added smoothness would cut wear on the transmission and other car sub assemblies. One mentioned that petrol consumption would increase slightly but the extra cost was overwhelmed by the savings in wear and tear.
These replies were unequivocal. I was quite surprised.
My prefered method of double-declutching was not the 'blip' or 'burst' method but just keeping the revs steady so that when you declutch the revs rise to what you want, raise the clutch, declutch and then let the clutch bite. It takes little practice and the difference is very noticeable to passengers. You end up doing it automatically.
It was suggested that it could be a safety feature in that there was no jerking, or sudden power off/power on which could cause the back to slide (RWD) such as on a corner. The Roadcraft method means you don't change gear on a corner anyway so I did no research on that.
My instructors were not hidebound followers of tradition and accepted that crossing hands on the steering wheel did not require the death penalty. Indeed, they were quite laid back on the System, but they all enforced the double-declutching rules.
We had an old Land Rover with either a non syncro box or one where it had given up the ghost, and you had to double-clutch on the way up. It was a good tet if anyone got a bit too cocky.
It doesn't add speed but if you want to push on with a nervous passenger then you can lull them into a false sense of security.
Despite being taught double-declutching some weeks ago now, let's see, that would have been 1979, I still do it. I had over 160,000 miles, a bit less than half being mine, on a clutch on my Volvo 240 and 150,000, well over half mine, on a Mondeo, both of which I towed with, and 145,000, about half mine, on a Rover 420. (I had the service history of all cars and none had had a previous clutch change - indeed the Rover had nothing done to it other than consumables.) I have no idea whether this is the norm or not but it seems pretty good to me.
The four things that a police driving school teaches are: System (the Roadcraft model), Safety, Speed and Smoothness.
We found no driver capable of being as smooth without double-declutching as with it, but some were able to get quite close. Not really conclusive evidence either way.
Then one of my instructors had the brilliant idea to contact all the gearbox manufacturers he could think of in this country and a number in the USA to canvas their opinions. One failed to reply. The rest were universal in their conclusion that double-declutching cut down wear on the gearbox and some had research (not shared) to prove it. Others mentioned that they would assume that the added smoothness would cut wear on the transmission and other car sub assemblies. One mentioned that petrol consumption would increase slightly but the extra cost was overwhelmed by the savings in wear and tear.
These replies were unequivocal. I was quite surprised.
My prefered method of double-declutching was not the 'blip' or 'burst' method but just keeping the revs steady so that when you declutch the revs rise to what you want, raise the clutch, declutch and then let the clutch bite. It takes little practice and the difference is very noticeable to passengers. You end up doing it automatically.
It was suggested that it could be a safety feature in that there was no jerking, or sudden power off/power on which could cause the back to slide (RWD) such as on a corner. The Roadcraft method means you don't change gear on a corner anyway so I did no research on that.
My instructors were not hidebound followers of tradition and accepted that crossing hands on the steering wheel did not require the death penalty. Indeed, they were quite laid back on the System, but they all enforced the double-declutching rules.
We had an old Land Rover with either a non syncro box or one where it had given up the ghost, and you had to double-clutch on the way up. It was a good tet if anyone got a bit too cocky.
It doesn't add speed but if you want to push on with a nervous passenger then you can lull them into a false sense of security.
Despite being taught double-declutching some weeks ago now, let's see, that would have been 1979, I still do it. I had over 160,000 miles, a bit less than half being mine, on a clutch on my Volvo 240 and 150,000, well over half mine, on a Mondeo, both of which I towed with, and 145,000, about half mine, on a Rover 420. (I had the service history of all cars and none had had a previous clutch change - indeed the Rover had nothing done to it other than consumables.) I have no idea whether this is the norm or not but it seems pretty good to me.
There have been loads of threads on this in the advanced driving forum.
Double declutching is unnecessary on modern cars and can do more harm than good, particularly if you don’t always get it perfectly right.
Certainly drivers should know how to, but most of us will never need it again. When I started driving some of the cars still in daily use didn’t have synchromesh on all forward gears. My first car didn’t and so I quickly learned. Some classic cars and the Formula Ford I later drove didn’t have them either. Such cars are now exclusively classics. Unless you are driving classics, you will never need it.
Did you mean heal and toeing? Matching the rev’s properly should be part of your repertoire.
Double declutching is unnecessary on modern cars and can do more harm than good, particularly if you don’t always get it perfectly right.
Certainly drivers should know how to, but most of us will never need it again. When I started driving some of the cars still in daily use didn’t have synchromesh on all forward gears. My first car didn’t and so I quickly learned. Some classic cars and the Formula Ford I later drove didn’t have them either. Such cars are now exclusively classics. Unless you are driving classics, you will never need it.
Did you mean heal and toeing? Matching the rev’s properly should be part of your repertoire.
Benjaminpalma said:
Thanks for your fulsome responses, chaps!!!
Yes, heel-and-toeing. Is that the same as double de-clutching but just getting the blipping smoother?
I know it's not necessary, I think it just sounds good coming up to traffic lights and country lane corners...
heel and toing is using the brake and throttle simultaneously to enable you to maintain engine revs whilst braking. Rev matching is part of that process but not all of it. Heel and toeing is much harder to do smoothly and in some cars pedal positions will make it impossible. You can reve match in any manual car. Yes, heel-and-toeing. Is that the same as double de-clutching but just getting the blipping smoother?
I know it's not necessary, I think it just sounds good coming up to traffic lights and country lane corners...
Double declutch is different steps as follows:
declutch and move gears to neutral
release clutch
blip throttle
declutch and select the gear you want
release clutch
Rev matching (down shifts only)
declutch
as gear lever travels through neutral blip the throttle (clutch still depressed) to raise the revs
select the lower gear
release clutch
Uncle Fester said:
Double declutching is unnecessary on modern cars . . .
The argument is not whether it is necessary but whether it has benefits. I've got to say that before my bit of research I favoured it being pointless. After it had to say that I did not have the conceit to ignore the opinion of almost all the major gearbox manufacturers in this and another country.As a point of interest, it was mentioned that all the replies came back from the USA before most of those from the British.
It can be of benefit in more ways than one but the main arugment for it is mechanical sympathy.
There is no suggestion that it is essential for fast driving or such, but it comes within the same remit as keeping the handbrake button depressed until it is fully on. It is not strictly necessary but it does stop wear.
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