Double declutching

[Slowly Slowly]

I'll have to come back to you on this one, I need to lie down in a dark room.

[RobM77]

Slowly Slowly said:

I'll have to come back to you on this one, I need to lie down in a dark room.

[GreenV8S]

Slowly Slowly said:

you can't mean blip the throttle with your foot on the clutch, please don't tell me you mean that.

I mean that.

[RobM77]

GreenV8S said:

Slowly Slowly said:

you can't mean blip the throttle with your foot on the clutch, please don't tell me you mean that.

I mean that.

yep - this is what everyone does unless they're in vintage cars.

[Deva Link]

Chris71 said:

Hi,

Can someone explain exactly how you should double declutch on a down change. As I udnerstand it, you

• clutch down
• into nuetral and clutch back up, so you've properly 'engaged' neutral
• raise the revs to spin up the layshaft
• clutch down
• back into (lower) gear and clutch up again

Having not tried it for a while, I seem to be having great difficulty doing this, but if raise the revs a second time, whilst the clutch is pressed down as you're going back into gear (ie during the penultimate step on the list above) it seems to work well. Produces a characteristic double blip of the throttle as you go down.

Am I really double declutching that way, or is it just leaving it to the syncromesh?

The second way you might as well not bother double-declutching - you're simply downshifting and matching the revs as you let the clutch back in.

As other posters have said, it's all about timing. You should be able to down shift by blipping the throttle in neutral without using the clutch at all - try that a few times (in someone else's company car!) and you soon learn to get the timing right. Pop the lever into neutral as you come off the gas, blip, then, if you get it right, it should glide effortlessly into the next gear down.

I double declutch when I'm (say) changing down on the approach to an A road bend, where I don't want to reduce speed, but do want to be in a lower gear for control purposes. I did this on a defensive driving day at work, and the instructor said it was the first time he'd ever seen anyone do it without being asked, so it must be pretty rare these days.

[GreenV8S]

RobM77 said:

I've often gone against the grain and received criticism on this forum by suggesting that it is important to always be as far away from the limit of adhesion as possible when driving on the road. Most advanced drivers on here seem to advocate doing what you want so long as you don't breach the limit of adhesion.

I think that minimising the forces on the vehicle and the demands you place on the vehicle are aims that most advanced drivers will share. I'd suggest 'usually' instead of 'always' though. There are very occasionally situations where it's desirable or even necessary to approach or exceed the limit of adhesion. These are pretty exceptional situations though.

[BertBert]

Deva Link said:

I double declutch when I'm (say) changing down on the approach to an A road bend, where I don't want to reduce speed, but do want to be in a lower gear for control purposes. I did this on a defensive driving day at work, and the instructor said it was the first time he'd ever seen anyone do it without being asked, so it must be pretty rare these days.

Was the instructor specifically congratulating you on the double-declutch or just the blip as you changed gear?

Bert

[BertBert]

Interestingly the double-declutch to help the synchro has different timing than a blip to raise the revs on the downchange.

The "double-declutch to help the synchro" approach has to have the blip when the clutch is up to raise the revs on the input shaft. You then put the clutch down to change gear. If it is a slow gearchange which is likley on an old/knackered synchroed car, you can actually lose the revs for the rev match and indeed go on to blip again.

The blip just to raise the revs can happen later in the process as the clutch doesn't have to be up and then be put down again. I have had some success teaching youngsters to blip by getting them to do it as they select the lower gear. I say "imagine you have to blip the throttle as you feel the resistance on the gear stick going through the gate into gear". Works a treat!

Bert

[Slowly Slowly]

RobM77 said:

GreenV8S said:

Slowly Slowly said:

you can't mean blip the throttle with your foot on the clutch, please don't tell me you mean that.

I mean that.

yep - this is what everyone does unless they're in vintage cars.

Right I've had a lie down and a think about this and I decided you are both wrong so I went to that great bible on the web and guess what?.

Tap in "single declutch", nothing comes up. Tap in double declutch and you get loads, I rest my case.................




I mean Youtube of course not Google.

http://www.youtube.com/results?search_query=single...

Edited by Slowly Slowly on Friday 13th July 19:05

[Deva Link]

BertBert said:

Deva Link said:

I double declutch when I'm (say) changing down on the approach to an A road bend, where I don't want to reduce speed, but do want to be in a lower gear for control purposes. I did this on a defensive driving day at work, and the instructor said it was the first time he'd ever seen anyone do it without being asked, so it must be pretty rare these days.

Was the instructor specifically congratulating you on the double-declutch or just the blip as you changed gear?

Bert

The double declutch - I got a special mention for having very smooooth gearchanges.

[BertBert]

that's because there is no such phrase as single-declutch. Just called heal n toeing.

If you watch Mr Vergers at work here....

http://www.youtube.com/watch?v=xTFRihT84Hs

You can see when he does a single downchange that there is no double-declutching going on!

Illustrated in a slightly slower yank tank here...
http://www.youtube.com/watch?v=ihCgxQnex5Q

Bert

[boxerTen]

Chris71 said:

Hi,

Can someone explain exactly how you should double declutch on a down change. As I udnerstand it, you

• clutch down
• into nuetral and clutch back up, so you've properly 'engaged' neutral
• raise the revs to spin up the layshaft
• clutch down
• back into (lower) gear and clutch up again

Having not tried it for a while, I seem to be having great difficulty doing this, but if raise the revs a second time, whilst the clutch is pressed down as you're going back into gear (ie during the penultimate step on the list above) it seems to work well. Produces a characteristic double blip of the throttle as you go down.

Am I really double declutching that way, or is it just leaving it to the syncromesh?

Once you've raised the revs to spin up the layshaft hold them there until the gear change is completed. The revs are already where you want them for matching the engine speed to the drivetrain. There is no point in letting them drop only to bring them back up a second time. This means keeping the throttle open just right, a little tricky, but probably smoother once perfected.

When the clutch goes in the second time the spun up layshaft starts slowing down, so you want the gear selected reasonably quickly, otherwise the syncromesh is going to have to spin it up again. The clutch can then come out at your leisure. No haste is needed since you are holding the revs constant with the throttle.

The next step is to do all of the above two or three times while braking heavily .

[GreenV8S]

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

[RobM77]

GreenV8S said:

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

True, but when people talk about a "heel and toe gear change" they're usually referring to a downchange with a single declutch, and during that single declutch the throttle is blipped. I've performed every downchange that I've done since the age of 18 like this, as have lots of other people.

[vonhosen]

RobM77 said:

GreenV8S said:

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

True, but when people talk about a "heel and toe gear change" they're usually referring to a downchange with a single declutch, and during that single declutch the throttle is blipped. I've performed every downchange that I've done since the age of 18 like this, as have lots of other people.

But most people doing a blip aren't heel & toeing, because they aren't on the brake while doing that blip.

[BertBert]

GreenV8S said:

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

Sorry I was illustrating the fact that there was not a term in common usage that is "single de-clutch". NOT saying HnT and the thing that doesn;t have a name, but we are calling the single declutch are the same!

Bert

[BertBert]

boxerTen said:

The next step is to do all of the above two or three times while braking heavily

That's why the raising of the revs by a blip is done when braking. It is extremely hard to maintain constant (raised) revs at the same time as braking (heavily). That's why the heel n toe uses a blip which is possible for mortals to do! Then you use timing of the gear and clutch to catch the revs at the right point.

Bert

[RobM77]

vonhosen said:

RobM77 said:

GreenV8S said:

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

True, but when people talk about a "heel and toe gear change" they're usually referring to a downchange with a single declutch, and during that single declutch the throttle is blipped. I've performed every downchange that I've done since the age of 18 like this, as have lots of other people.

But most people doing a blip aren't heel & toeing, because they aren't on the brake while doing that blip.

Surely it depends what you're doing? If you're changing down wilst braking, it'll be a blip with the side of the foot, but if you're just knocking down a gear without braking, say to overtake someone, or when just cruising down a road gently, it'll be a blip with the whole foot without braking. Both techniques are trivially easy (once learnt), so you just apply whichever technique suits the situation.

[vonhosen]

RobM77 said:

vonhosen said:

RobM77 said:

GreenV8S said:

BertBert said:

that's because there is no such phrase as single-declutch.

Agreed.

BertBert said:

Just called heal n toeing.

No, they're completely different techniques, which may be used separately or together.

True, but when people talk about a "heel and toe gear change" they're usually referring to a downchange with a single declutch, and during that single declutch the throttle is blipped. I've performed every downchange that I've done since the age of 18 like this, as have lots of other people.

But most people doing a blip aren't heel & toeing, because they aren't on the brake while doing that blip.

Surely it depends what you're doing? If you're changing down wilst braking, it'll be a blip with the side of the foot, but if you're just knocking down a gear without braking, say to overtake someone, or when just cruising down a road gently, it'll be a blip with the whole foot without braking. Both techniques are trivially easy (once learnt), so you just apply whichever technique suits the situation.

Yeah but blip without braking isn't heel toeing, blip whilst on the brake is.

[GreenV8S]

BertBert said:

Sorry I was illustrating the fact that there was not a term in common usage that is "single de-clutch". NOT saying HnT and the thing that doesn;t have a name, but we are calling the single declutch are the same!

Bert

I understand now.