What is double cluthing?
Discussion
neilski said:
Dude, you could write that about every question ever posed.doogz said:
Clutch in, out of gear into neutral, clutch out. Clutch back in, select gear, clutch back out.
Back when crash boxes were the norm, synchromesh gearboxes weren't commonplace.
Still do it in my 4x4 and truck when it's cold, only really on downshifts though, upshifts it doesn't mind.
If downchanging you need to blip the throttle while the clutch is engaged in neutral before declutching again and engaging the next gear down. This brings the gearbox internals up to the speed needed to allow quiet engagement of the lower gear. Changing up, however, is exactly as you describe. "Clutch in" and "clutch out" are ambiguous terms; "clutch down" and "clutch up" is clearer and these mean "declutch" and "re-engage clutch" respectively. Back when crash boxes were the norm, synchromesh gearboxes weren't commonplace.
Still do it in my 4x4 and truck when it's cold, only really on downshifts though, upshifts it doesn't mind.
Double-clutching is typically favoured by pub bores, often seen pottering about in their old MGs with cloth caps and leather driving gloves. I can't help wondering how such dynosaurs would cope with cars like the Nissan 370Z which can blip the throttle for the driver during a downchange!
At the other extreme, beware the pub bores who bang on about the attractions of fitting a "short-shifter" to achieve faster gearchanges. These mechanisms rush the synchromesh and lead to accelerated wear.
At the other extreme, beware the pub bores who bang on about the attractions of fitting a "short-shifter" to achieve faster gearchanges. These mechanisms rush the synchromesh and lead to accelerated wear.
[quote=doogz]
New cars have gearboxes with synchromeshes, so yeah, it's not really required.
[quote]
Haven't tried this ofr a long time, maybe new syncro is better, but it used to be that if you are running round te red line the synchro won't keep up so the only way to get into a gear is by double declutching, and I think, race boxes didn't/don't have synchro so it is necessary on them.
I agree that it can be a pub bore thing if about a modern car, but tyr driving a pre war one without knowing how to do it and you may have a bit of trouble!
New cars have gearboxes with synchromeshes, so yeah, it's not really required.
[quote]
Haven't tried this ofr a long time, maybe new syncro is better, but it used to be that if you are running round te red line the synchro won't keep up so the only way to get into a gear is by double declutching, and I think, race boxes didn't/don't have synchro so it is necessary on them.
I agree that it can be a pub bore thing if about a modern car, but tyr driving a pre war one without knowing how to do it and you may have a bit of trouble!
Ozzie Osmond said:
Double-clutching is typically favoured by pub bores, often seen pottering about in their old MGs with cloth caps and leather driving gloves. I can't help wondering how such dynosaurs would cope with cars like the Nissan 370Z which can blip the throttle for the driver during a downchange!
They'd probably be bored silly and fallen asleep at the wheel within five minutes.
Where's the fun and skill requirement in a car that drives itself
I always thought it was double de-clutching.
It's satisfying because doing that combined with a squeeze or blip on the throttle can aid really smooth down-changes, as in even smoother than an auto, plus it helps the box out a bit rev matching while you do it. After that it's heel and toe so you can brake, clutch to neutral match revs clutch up, clutch down slot gear, then back on power so you brake on the pedal (without engine braking) and blip with the same foot to maximize your throttle response. Naturally you have to do this quick - just look at some old rally vids and watch their feet, it's not too hard to do the basic change and blip but it's very very hard to master it like a professional so that it's second nature. I'm no master btw and someone else would probably explain this much better than me.
I find double de-clutching useful on my landy and cars without syncros too in the past. I used to do it a lot on my MX5 too, because during the winter the box was very stiff into second and double de-clutching assisted the gear change. Also useful to assist on dropping to first gear on most cars I've driven too.
It's satisfying because doing that combined with a squeeze or blip on the throttle can aid really smooth down-changes, as in even smoother than an auto, plus it helps the box out a bit rev matching while you do it. After that it's heel and toe so you can brake, clutch to neutral match revs clutch up, clutch down slot gear, then back on power so you brake on the pedal (without engine braking) and blip with the same foot to maximize your throttle response. Naturally you have to do this quick - just look at some old rally vids and watch their feet, it's not too hard to do the basic change and blip but it's very very hard to master it like a professional so that it's second nature. I'm no master btw and someone else would probably explain this much better than me.
I find double de-clutching useful on my landy and cars without syncros too in the past. I used to do it a lot on my MX5 too, because during the winter the box was very stiff into second and double de-clutching assisted the gear change. Also useful to assist on dropping to first gear on most cars I've driven too.
RV8 said:
- just look at some old rally vids and watch their feet
Can't find this on youtube, but TG did a thing with McCrae, showing his feet, stepping between double declutching and left foot braking. Clarkson said something like 'He can do all the driving without having to think about it, which is why he can practice some Irish dancing at the same time'DannyVTS said:
I usually always double clutch when coming down the gears towards a roundabout when I won't be coming to a complete stop
Just feels nicer on the car and im sure the clutch is a lot happier ? N
There's no point though. You may as well just rev match normally. If you are braking at the time then you would heel and toe, else you'd just rev match.Just feels nicer on the car and im sure the clutch is a lot happier ? N
There is no point in double de clutching in a car with synchromesh.
doogz said:
Accelerated wear, yes, but in a track car/race car, you're not exactly doing that many miles. If you want to track a 5spd MINI, a gearbox basically becomes a service item, synchro's are the least of your worries!
Quoted for truth. The 5 speed MINI box is made of chocolate.Handy for rwd cars if your pressing on, trackdays or racing especially in wet conditions, typically used with heel & toe. Especially usueful for high rpm downchanges.
Being in the passenger seat of a driver who does it on track is quite noticeable as it makes for much smoother downshifts, its makes for faster downchanges too on most old school agricultural gearboxes, not applicable to modern day stuff really.
A lot of modern high performance DSG type boxes do it for you, eg Lexus ISF/LFA have a lovely down blip action on the throttle. Its doing it for you
Being in the passenger seat of a driver who does it on track is quite noticeable as it makes for much smoother downshifts, its makes for faster downchanges too on most old school agricultural gearboxes, not applicable to modern day stuff really.
A lot of modern high performance DSG type boxes do it for you, eg Lexus ISF/LFA have a lovely down blip action on the throttle. Its doing it for you
john2443 said:
and I think, race boxes didn't/don't have synchro so it is necessary on them.
True, but the standard advice for a dog box is to single clutch rev match and just do it as fast as possible. I don't know of any racing drivers who double declutch with a dog box.Mr Hewland Big Cheese Hewland CEO guy said:
Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement. He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible. In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle.
Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
http://www.hewland.com/svga/advice.htmlAnother method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
Sorry for the long post, but I thought some might find the above interesting.
RobM77 said:
john2443 said:
and I think, race boxes didn't/don't have synchro so it is necessary on them.
True, but the standard advice for a dog box is to single clutch rev match and just do it as fast as possible. I don't know of any racing drivers who double declutch with a dog box.Mr Hewland Big Cheese Hewland CEO guy said:
Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement. He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible. In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle.
Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
http://www.hewland.com/svga/advice.htmlAnother method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.
The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`.
Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car.
Sorry for the long post, but I thought some might find the above interesting.
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