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I've recenlty started double-declutching again after years of not bothering. My dad taught me to do it when I was learning, but is there any mileage in it, with modern synchro-mesh, or am I just going to burn my clutch out instead of my gearbox? Car is an 11 year old Focus estate....
I can't see the point of it myself.
or am I just going to burn my clutch out instead of my gearbox?
Won't it be the gearbox that you wreck?
double declutching on a down shift still has some merit in matching engine and gearbox speed and reducing clutch wear whilst they get back into step but given modern synchromesh it's irrlelvant as far as reducing gearbox crunching etc is concerned.
and it stops you left foot braking as easily as well 😉
Still do it all the time, but agree seems utterly pointless.
Was funny when driving small cars and revving harder, but now I have
a big turbo diesel.
J.
My Dad taught me the opposite, I now only use the clutch to change up when I'm trying to get away a little quicker than usual. In normal driving I don't use it at all.
how does this work????
My experience of double declutching is that it's used solely by a) vintage car drivers who have to do it, b) race drivers with tiny flywheels, and c) smug gits who think it makes them superior.
cruzheckler - you depress the clutch once to put the gearbox into neutral, let the clutch back out, depress it again, select gear, let clutch out again.
Don't think I'll bother now though...
EDIT - Cougar - you may be on the money re the vintage car thing - my dad has a bit of a fleet of vintage cars / commercial vehicles / taxis but he's not overly smug!
[i]race drivers with tiny flywheels[/i]
I know this isn't a euphamism, but it ought to be 😉
The Institute of Advanced Motorists stopped using double de-clutch shifting some years ago as it puts excessive wear in the clutch pinion bearing (IIRC).
As has been said, it's not necessary with modern synchro boxes. The Police advanced driving test continued using it for some time after (not sure if they still do) as it promotes unhurried shifts.
There's no advantage to using it, unless you like the satisfying feeling of blipping on the down-shift. Heal-and-toe rev-matching is more fun and more use IMHO.
[i]cruzheckler - you depress the clutch once to put the gearbox into neutral, let the clutch back out, depress it again, select gear, let clutch out again.[/i]
you're supposed to rev the engine slightly between clutch dippings to get the engine,gear box and road speeds get into step too.
My Dad taught me the opposite,
Never saw the need / point in a car (other than "because I can", see c) above), but it certainly makes for considerably smoother, faster changes with a bike's fully synchronous gearbox. After a while, I never touched the clutch for upchanging other than setting off, just hook a toe under the lever and press gently, match the revs on the throttle and the gear just plops into place.
Are you actually double declutching? This involves pressing the clutch to disengage the gear, letting the clutch right up, then pressing it again to engage the next gear. If so, it's a waste of time with modern syncromesh gearboxes.
If you are going a blipped throttle downchange, i.e. blipping the throttle while the clutch pedal is depressed, then that is a good thing as it matches engine speed in the new gear to wheel road speed. It's not necessary but good practice. Most effectively done by heel-and toeing as said above. All the new flappy paddle boxes do this on downchange
Where's Surfmatt??
ust hook a toe under the lever and press gently
You what now?
Bike, Mol.
Oh, the gear change lever.. right.. never could get the hang of gear changes on motorbikes. One down four up.. wtf..
cruzheckler, not sure how to describe it without a demo but you match the revs to the speed and have minimal presure the gears then just slip the stick across. Google "float gears" for a better explanation.
It is effectively what those paddle-shift gearboxes are doing.
Not really. The VW DSG has two gearboxes and two clutches to switch between pre-selected gears.
Not something you can do yourself on a car with one gearbox 🙂
One down four up.. wtf..
It's to stop you accidentally shifting into neutral.
It's to stop me riding motorbikes. That's the real reason.
Although.. woudl shifting into neutral accidentally not be far more benign than shifting into first accidentally?
Well,
If you're rapidly rattling down through the gearbox, it's generally to get to first. I can't readily see any reason you'd want to get to neutral in a hurry, and I wouldn't relish the idea of suddenly needing to apply power and finding I was out of gear.
TurnerGuy - Member
It is effectively what those paddle-shift gearboxes are doing.
molgrips - Member
Not really.
Yes it is. Agreed the VAG DSG boxes are double clutch but that's irrelavent to the point that TurnerGuy and I were making. As per my previous post, they do a throttle blip on the downchange to match engine and road speed.
Only actually necessary when you are driving at the limit, which you shouldn't be on public roads, but it is satisfying, and I do it all the time.
Fair point (I'm not concentrating well this afternoon). However, when changing down don't we all apply throttle as we let the clutch in, unless actually on the brakes at the time? Very jerky otherwise.
Yes it is
no its not
Throttle blip to match engine/road speed is one thing. Makes letting the clutch out smoother so everyone does it.
Double de-clutch matches gearbox input and output shaft speed, usefull if you have no syncromesh to do the job for you.
Shifting without the clutch is possible as the input shaft is still spinning (attached to the engine by the unusued clutch) so as long as the engine is allowed to slow slightly the input and out spin aproximately the same rates.
Full throttle changes can be done on a motorbike because the engine weighs **** all so as long as the ECU cuts the spark (on a new bike or one with a quickshifter) when it senses the shift or the rider closes the throttle momenteraly, the engine just matches the road speed very quickly. Some kit car/track car/race car gearboxes can do this, but need to be pretty beefy, so not advisable to try it on the road.
As has been said, it's not necessary with modern synchro boxes. The Police advanced driving test continued using it for some time after (not sure if they still do) as it promotes unhurried shifts.
North Wales Driving school were teaching it up to a few years ago but even they may have binned it off now as a waste of time.
Last advanced course I did taught keeping the revs up as soon as you dip the clutch when doing an unhurried downshift to smooth it all out- sounds odd but works
I learned to drive in an old crappy 950cc MkII Fiesta. Throttle on downshifts was essential to keep passengers and driver happy. That car taught me a lot about how to drive smoothly because it was so difficult!
This was supposed to be a troll thread right?
Throttle blip to match engine/road speed is one thing. Makes letting the clutch out smoother so everyone does it.Double de-clutch matches gearbox input and output shaft speed, usefull if you have no syncromesh to do the job for you.
Nope. How many people blip the throttle in the middle of a gearchange - practically none. Of course everyone lets the clutch out gradually and helps by gradually pressing the throttle - that's normal driving. A blipped throttle downchange achieves the same thing but because of the blip it allows much quicker shifting while matching input and output shaft speeds. That's why it's still used in racing and sequential manual boxes like the DSG.
Double de-clutching is not the same as blipped throttle downchange. It has the extra element of letting the clutch up when in neutral and then pushing down again to shift to the new gear, and is only required for non-sycromesh boxes
That's why it's still used in racing and sequential manual boxes like the DSG
Mine does not blip the throttle between gear changes. It's never in neutral, this can't happen.
It brings the revs up to match the road speed in the new gear - is that what you mean?
A blipped throttle downchange achieves the same thing but because of the blip it allows much quicker shifting while matching input and output shaft speeds
No its not, because the input shaft is to all intents and purposes stationary when the cluch is pressed and the box in neutral.
You could blip the throttle and double clutch, but thats just making the input shaft spin even faster.
Quite interesting side point:
Towing a RWD car can ruin the gearbox, some designs rely on the input shaft spinning to get the oil where its needed.
Quite interesting side point:
Massive over sell there!
Things my Dad taught me
Double De-Clutching
Heal & Toe
Left Foot Braking
Lift off oversteer
Racing gear changes! (up shifting without clutch, a lot of crunching learning this one!)
Then after my driving test he put me on a skid pan.
The only thing I really use occasionaly is double de-clutching on the downs as I find it smoother, if done correctly.
This was supposed to be a troll thread, right?
No 🙁
One useful thing my stepdad taught me recently, is to give a good burst of throttle just before the apex of small humpbacks on roads (plenty of these where he now lives on Skye). The effect (in theory) of this, is that it compresses the springs and ensures you don't take the sump out on the downside / dip of the hump, because by that time the springs are all pushing back up.
What's more, it actually works IM (real world) E. gets a tad scary if there a few in quick succession as you can end up doing 70 on a singletrack road....
A "racing up shift" uses the clutch. You lift just enough to stop the engine over revving as you dip the clutch, shift and dump the clutch. This is faster because not only can you do it quicker than clutchless but you also recover the energy stored by the flywheel. Not a good idea if you pay for your clutch plates and fuel.
The only time I changed clutchless was in a FWD rally car when changing down and left-foot braking. It was simply a case of leaving my foot on the floor and moving the lever as fast as possible - I could only do it fourth to third. I only did this in extremis and used the clutch whenever I could free off my left foot.
I learned to double de-clutch as the 1960 car had a crash box but dropped the habit when I got a car with sychromesh. I still heel and toe but curse myslelf as it's a waste of fuel and unnecessary when pottering around.
My mum taught me all this but it was my dad that taught me refinements such as the unintentional high-speed spin.
One useful thing my stepdad taught me recently, is to give a good burst of throttle just before the apex of small humpbacks on roads (plenty of these where he now lives on Skye).
There's one like that between March and Benwick in Cambridgeshire. First time I drove along it was in my Puma; faced with a perfectly straight road and no traffic I stuck my clog in. After nearly losing the damn thing off the top of a very pronounced hump where a side road joined, I found it much easier to drive along the dotted line!
cant say i have ever understood doubledeclutch.
i think, because, despite being very good with mechaical things (you will just have to take my word on that) i just cant get my head around what the damn thing is doing in there!
i always always try and match the engine speed to the wheel speed, well enough so i can drop the clutch instantly, and have no jolt in the transmission (rather than slipping it slightly)
when driving twistier roads, this often involves blipping the throttle, and heel and toeing into the corners to change gear without upsetting the balance. Just because i can.
So i get matching the wheel speed to the engine speed.
what does double de clutch do that a throttle blip doesnt?
I just like the satisfying throttle blip and the slightly faster downshift approaching a bend (20 year old box likes to be treated nicely)
Olly, it matches the input shaft speed to the output shaft speed without contact, meaning he syncro cones don't have to force the input shaft up or down to speed while the clutch is pressed (which is what happens with a normal shift).
What coffee king said.
Normal driving in a normal modern car:
1)clutch in, engine disengaged from gearbox input
2)shift to neutral, there are now 3 parts to the system moving independantly, the engine and flywheel, the clutch plate and gearbox input shaft, the output shaft of the gearbox.
Depending on design theres alos various dog gears, lay shafts etc, but we'll ignore those and just assume its a 2speed+reverse in a nice simple box.
The output shaft spins at the road speed.
The engine spins at whtever you let it.
The input shaft stops (not entirely, but 'box oil is pretty thick so its slowed enough compared to the 6000rpm+ it was doing a split second ago and thr 4000rpm you want it to do after the upshift)
3)Shift into the next gear and the two gears (output and input shafts) are at different speeds, to you have 2 brass 'cones' between them, as you push them together the input shaft speeds up, the further you get towards the gear the faster it spins untill they match just as the gears are about to engage.
4)Hopefully the engine revs now match your road speed (you've been off the throttle a split second) so when you relsease the clutch the input shaft is moving the same speed as the engine an everything is nice and smooth.
[b][u]double clutch method[/u][/b]
As above, but,
After (2), release the clutch quickly and press it again, this conects the input shaft to the engine again and gets it spinning, as the pedal comes up push it into the new gear, as both are spinning the syncro cones do no work, and everything meshes smoothely.
Basicly the clutch slips rather than the cones, and if you've ever tried clutch plates are easier to change than a gearbox rebuild.
TBH, I've never bothered, even in the midget, full throttle, clutch down about 3/4 of the way (to the bite point so the input shaft never stops spinning), next gear, revs have rissen as the load came off the engine so the flywheel gives the whole car a kick up the arse as you let the clutch out.
If your Midget has either the A-series or Triumph engine then you'll be changing up at between 5800 and 6100. Now if the revs rise from there it is not a good thing. On full throttle I can't see you changing quickly enough to keep the thing below 6500 which is abouh the point valve bounce will start, a very bad thing.
I run out of nerve/mechanical sympathy kicks in arround 5 (that and a nasty missfire from a cheep condenser starts arround 5k) 🙁 Not somethign I do very often, just when, I fancy a bit of stupidity, normaly I'm a pootler getting silly mpg out of it on a sunny afternoon with the roof down 🙂
Let the throttle off, but not enough to let the engine speed drop might have been a better description than full throttle.
so in thicko summary.
syncro and gearbox layout is as i understood it
the syncro COULD be thought of as a "kind of" clutch between the actuall clutch, and the road wheels
double de clutch, re engages the input briefly to maintain the spin of input, to REDUCE wear on the syncro (mini internal clutch, and transfer it to the ACTUAL clutch (by doubling clutch use per change)
?????
assuming i've got it right (or near enough) its one of those things that, while it helps the car last longer, it doesnt help the driver at all? (where as blipping, and heel and toe, keeps the car/drivechain from jolting and pushing the car around)
Tempted to try clutchless shifting in my car, as i can chuck gears in bob on (most of the time :$ but I cant get over the fear or making mechanically sinful noises, so have never tried, and that is probably just as well.
It doesn't really help at all unless a) you are a racing driver b) your car is really really old and has no synchromesh or c) your car is a bit knackered.
On the above mentioned old fiesta 3rd to 2nd would give a little crunch now and then. Double de-clutch made it smooth as.
For clutchless shifting, just make sure you're really light with the lever. If the speed's not right it just won't go in, there'll be no crunch unless you continue to try and ram it home.
The other alternative is to slam it into gear as hard as you can but that's not recomended 🙂