ausmini :: View topic - double declutching

you heel toe to reduce the time the synchro has to work to mesh the gear and reduce wear on the synchromesh

Spaceboy wrote:

you heel toe to reduce the time the synchro has to work to mesh the gear and reduce wear on the synchromesh

I accept what MiniMad was saying and it occured to me while writing the answer to the MK1 Cooper S question and thinking about the relationship b/w the clutch and the input shaft and the gears. I'll modify my driving style now.

BUT I reckon Spaceboy's statement above is not quite right. Heel in toe is useful to maintain a smooth power curve and remain on cam and maybe avoid that jerk of power when downshifting

Vizard?? That book was written in the 80's, it's been 25years Chong, there's been 25 years of development since then

I don't know about you guys, but I just used to bounce through second on my way to first on my 3 synchro box.

ie. back from 3rd to second (only enough to feel resistance, not actually engage second) and up to first. All done in a smooth motion. It's pretty easy.

The synchro on second would do the work of matching the gear speeds.

Author:	Mike [ Wed Jun 13, 2007 2:16 am ]
Post subject:	double declutching - opinions
I've two questions as usual: I've always been double declutching (or heel in toeing ) with the mini (busted 2nd synchro when I bought it and just continued with it after the gearbox rebuild) and my system has always been press the brakes slightly with the toe while blipping the throttle with the heel and at the same time press the clutch move the gear stick to neutral and continue to a lower gear - all that without letting go off the clutch untill the lower gear is engaged. (atleast thats what I believe I do, as the action is so subcontious its hard to visualise). I think that in reality it works out that I blip the throttle while slowly releasing the clutch with the lower gear engaged. This works fine for me but I keep hearing repeated references that the correct way to doube declutch is to press the clutch, engage neutral, release the clutch, blip the throttle, press the clutch again, engage the lower gear. I was just wondering what everyone else uses? Also what are the dissadvantages of double declutching in terms of engine/g'box wear etc?

Author:	Spaceboy [ Wed Jun 13, 2007 3:06 am ]
Post subject:
if you only press and release the clutch once, its not double clutching. you heel toe to reduce the time the synchro has to work to mesh the gear and reduce wear on the synchromesh

Author:	Mini Mad [ Wed Jun 13, 2007 6:15 am ]
Post subject:
See my post in ben's thread. The reason you release the clutch pedal in neutral is so that drive from the crank -> flywheel -> clutch is transferred to the gears therefore allowing you to spin the gears matching them to your next gear choice. Revving the motor with the clutch in will do nothing to the gearbox and it's only merit is that if matched right you would still get the benefit of a smooth gearchange the wont unbalance the car - but the syncro is still doing all the work - you've just matched the motor to the new gear speed instead of matching both the motor and the gears. There are a few schools of though - with a 4syncro box it's hardly a requirement to double clutch and most do simply what your doing and just blip the throttle on down changes. There are those that double clutch all changes - like me - but i kinda learnt how to do it when i was 16 and i had a worn 2nd gear syncro and it's been one of my built in driving habbits ever since. There are those that dont bother at all with either as well. Doing it properly is very rewarding and a throttle blip of dellorto fed music never hurt anyone

Author:	Mike [ Wed Jun 13, 2007 6:28 am ]
Post subject:
Spaceboy wrote: you heel toe to reduce the time the synchro has to work to mesh the gear and reduce wear on the synchromesh I accept what MiniMad was saying and it occured to me while writing the answer to the MK1 Cooper S question and thinking about the relationship b/w the clutch and the input shaft and the gears. I'll modify my driving style now. BUT I reckon Spaceboy's statement above is not quite right. Heel in toe is useful to maintain a smooth power curve and remain on cam and maybe avoid that jerk of power when downshifting

Author:	Mini Mad [ Wed Jun 13, 2007 6:38 am ]
Post subject:
Mike wrote: Spaceboy wrote: you heel toe to reduce the time the synchro has to work to mesh the gear and reduce wear on the synchromesh I accept what MiniMad was saying and it occured to me while writing the answer to the MK1 Cooper S question and thinking about the relationship b/w the clutch and the input shaft and the gears. I'll modify my driving style now. BUT I reckon Spaceboy's statement above is not quite right. Heel in toe is useful to maintain a smooth power curve and remain on cam and maybe avoid that jerk of power when downshifting I agree with Ryan on this one - there are a couple of reasons for double clutching. 1. To match gear speed so the syncro doesn't have to (ie reduce the time it has to work to mesh the gear or if you are spot on stop this need completely) 2. For a smoother drive - diving deep on the brakes coming into a corner the last thing you want is to unbalance the car - by matching the revs there will be no jerk/lunge from the car which would happen if you didn't double clutch while downshifting. Though you typically want to get all your gear changes out of the way before the corner - it still helps keep the car settled under hard braking. I cannot see how heel and toe maintains a smooth power curve as that is a product of the engine, perhaps you were talking about the jerk when releasing the pedal? - it also does not make you remain on cam - as the action of change down a gear that keeps you on cam - not the double clutch/heel toe action...that i can see anyway this early in the morning..

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Author:	Drewus [ Wed Jun 13, 2007 7:12 am ]
Post subject:
I used to "overcome" a bad synchro on 3rd gear by either double clutching, or simply performing a slower gearchange. Odd thing is that i still do slower gearchanges between 4th and 3rd no matter what car i drive, it just became second nature. No idea why it worked, but it did.

Author:	Spaceboy [ Wed Jun 13, 2007 7:59 am ]
Post subject:
agreed, and i think heeltoe can also reduce wear on the clutch plate

Author:	andbat [ Wed Jun 13, 2007 8:02 am ]
Post subject:
i'm not sure what i do exactly but if i don't 3rd-2nd crunch. i think i just blip but without the brake. so there is split second where i am not braking while slowing down. i'm gonna have to experiment on the way to school now

Author:	Lillee [ Wed Jun 13, 2007 10:14 am ]
Post subject:
Hello... just to clear up some misconceptions: Heal toeing is heal toeing. Double clutching is something else again. Heal toe is described by the first post. Double cluchting is clutch in, brake, neutral, off clutch, blip throttle, clutch, lower gear. Hence the term "Double" clutch cause you clutch twice. By revving with the clutch in, all you do is wear the throw out bearing, esp if it is not set up properly. Once the clutch is disengaged (pedal down), there is no more friction on the plate as all of this movement of the flywheel is transferred to the throwout bearing. Heal toeing will not save the clutch plate anymore than normal gear changes. What it does do is wear the throw out bearing by putting more load on the bearing as you are blipping the trottle. Double clutching will not save the clutch plate, in fact it will reduce it's life as you are using it for friction contact twice per gear change so arguably it is worste. What both heal toe and double clutch do is save synchros as it matches the engine speed to the gearbox before you change to a lower gear, therefor less reliant on synchro. This is useful mainly for racers with dog boxes, trucks that have no sincros, and old historic racing cars with no synchro boxes. Hardly a necessity for 4 synchro boxes or modern cars, and.. you are probably doing more dammage than good if you miss... Then you have to ask yourself: what's worste, a busted synchro that needs changing once every 100,000 miles, or rebuild your engine due to excessive wear because you are constantly using more revs every gear change? hrmmm

Author:	Lillee [ Wed Jun 13, 2007 10:27 am ]
Post subject:
pristic wrote: Forget Vizard... Graham Russell wrote: Vizard?? That book was written in the 80's, it's been 25years Chong, there's been 25 years of development since then

Author:	Tadhg [ Wed Jun 13, 2007 10:39 am ]
Post subject:
Chong's right. Double clutch downshifting does wear throw-out bearings - I killed one because of it. And it does wear the clutch plate a bit more, but not too much more, because, although you're using it twice per gearchange, it's only got load from the input shaft of the gearbox for the extra time you're using it. And the odds are that your revs are better matched the second time you use the clutch (when you have engaged the gear and are reconnecting the engine to the road) than if you didn't rev-match (which is what you are trying to do when you double clutch). So the question stands - do you want to repair a synchro a little less frequently, or the clutch more frequently? Heal and toe is a technique which, whilst not being the same as double clutching (you can heal and toe without doubling the clutch), is the most effective way of double clutching, as double clutching, as discussed everywhere, whilst it can be done on upshifts, is mostly pointless. If you change fast enough, the gearbox's revs won't have dropped too far anyway. So Andbat, you may well be double clutching, but not doing heal and toe. In terms of slowing a gearchange, that can work with a dying synchro. Synchros have an optimal speed for changes - even in a modern car it's possible to "beat" a synchro, to change gear so quickly that the synchro can't keep up and you crunch the gearset. So slowing down your shift gives the synchro more time to work to match the gear speeds. I've had similar experiences, with Mini boxes and Commodore boxes. For mine, the decision about double clutching is easy. I don't like the idea of taking the engine off the box - sounds like too much work! The clutch isn't hard to fix (or get fixed). If one extra clutch gives you 25% more gearbox life, for mine it's probably worth it. Others will disagree. Plus, I learned to drive in a Commo with a mostly dead second gear synchro and a dying third gear synchro. I didn't have anyone to show me how to do it, and, although I'd read about it, I didn't fully understand how to do it until I saw someone do it - it was an old clip of someone in the 6 wheeled Tyrrell F1 car, and they showed his feet. There's a tip for anyone wanting to learn - pay attention next time they show a driver's feet on TV - unless of course they're showing how he's flat shifting... I've done the heal and toe ever since. It sounds fantastic, it's part of the art of driving a car (a part that is now dying). I do rev the engine when the clutch is in, but that's purely to get it up towards where it needs to be when the car's in neutral - I start revving with the clutch in and let the clutch out before I hit the revs I want. Clutch back in, rev, then let clutch out with car in gear as the car gets to the revs I want, so I'm not revving the engine against the brakes. Oh, and although we say heel and toe, it's often more the ball of the foot on the brakes and the side of the foot on the accellerator - it's a bit hard and pointless to twist your leg that far! Although Cameron McConville once wrote that he did a CAMS test with someone (as the inspector) and the bloke used his heel on the brake and toe on the throttle, stopping from 200km/h in a Valiant!

Author:	Blokeinamoke [ Wed Jun 13, 2007 10:46 am ]
Post subject:
Double clutching only saves the syncro - the double dip on the clutch would increase wear I suppose. In the limited driving I have done on the Moke I double declutch because the change doesnt feel positive - so you can make sure you get a gear before letting it out. Nothing to do with syncro for me. Heel Toeing is just more fun. Sort of like tap dancing and driving at the same time. I only heel toe going down the box - no point when going up Now try double declutch heel toe whilst doing the samba thats a challenge

Author:	bnicho [ Wed Jun 13, 2007 11:02 am ]
Post subject:
Just about every Mini I have had has suffered sychro issues at some stage. I learnt pretty early on to double-declutch and heel and toe in Minis. Now as soon as I hop in one, it just happens instinctively. (Except the Moke of course - it's Autio ) I find I can't double-declutch my Coronas as easily - the pedals are too far apart for my heel-toe method.

Author:	Mick [ Wed Jun 13, 2007 11:17 am ]
Post subject:
I don't know about you guys, but I just used to bounce through second on my way to first on my 3 synchro box. ie. back from 3rd to second (only enough to feel resistance, not actually engage second) and up to first. All done in a smooth motion. It's pretty easy. The synchro on second would do the work of matching the gear speeds.

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Author:	Tadhg [ Wed Jun 13, 2007 11:49 am ]
Post subject:
Mick wrote: I don't know about you guys, but I just used to bounce through second on my way to first on my 3 synchro box. ie. back from 3rd to second (only enough to feel resistance, not actually engage second) and up to first. All done in a smooth motion. It's pretty easy. The synchro on second would do the work of matching the gear speeds. I was taught to do that and tried it, but I picked up heal and toe more easily... Couldn't consistently find that sweet spot on 2nd's synchro. And it wears your 2nd gear synchro more, which is already the hardest working synchro. Plus, heal and toe double de-clutch downshifting sounds more impressive to say, and sounds more impressive when you're driving!