Ok, so I just taught myself how to double clutch heel and toe and I find it extremely entertaining. I know the idea behind double clutching is to get the lay shaft spinning the same speed as the engine and drive shaft so that the syncros are less stressed, but my question is this: In the real world, is that really going to help your tranny that much? I mean, on paper it helps, and I'm sure it does in the real world, but is it really that much?

I will say though, that just for fun's sake, I cant see myself going back to single clutching.

Given that I have a car and a bike roughly as old as myself that have probably had the nuts driven off them at some stage (I know the bike has anyway ), and both have never needed any sort of gearbox work other than new clutches, I'd say it has minimal effect. I do tend to rev match when downshifting, but not double clutch...

Actually, I've taken to clutchless shifting recently. I've found at about 5k in every gear bar first, I can shift up clutchless with zero resistance, which I've been told means everything is syncro'd at that speed. I haven't noticed any strange noises or feel when driving, and I've also been told it lessens the wear on the syncros, as long as you have the revs matched. How accurate that is, I don't know

double declutching is something

• many people believe to be doing correctly, even if they're not
• that needs practice (and loads of it!) to outperform a synchromesh in matching revs, simply because it takes a lot of time to declutch/engage/declutch/engage all in the same time the synchros would need

That said, it does give you more control and allows for smoother gearchanges, even if they're slower.

Quote from dougie-lampkin :

Actually, I've taken to clutchless shifting recently. I've found at about 5k in every gear bar first, I can shift up clutchless with zero resistance, which I've been told means everything is syncro'd at that speed. I haven't noticed any strange noises or feel when driving, and I've also been told it lessens the wear on the syncros, as long as you have the revs matched.

I know I've done that just to screw with the minds of people who dont understand how to drive standard, and it can be entertaining, but I've never heard about the being better on syncros thing, but I guess it might keep the lay shaft spinning at the same speed. I'm def. not saying that you're wrong, I'm just saying that I've never heard it.

Quote from morpha :

double declutching is something

• many people believe to be doing correctly, even if they're not
• that needs practice (and loads of it!) to outperform a synchromesh in matching revs, simply because it takes a lot of time to declutch/engage/declutch/engage all in the same time the synchros would need

That said, it does give you more control and allows for smoother gearchanges, even if they're slower.

Yeah, I spend around 2 hours in a big empty parking lot practicing 3-2-1 double clutching, and it feels to be just about right (it also looks exactly the same as the times that I've seen my grandpa do it, and he's been to quite a few perf. driving school), but thats not to say that it is. My double clutch heel toe down shifts do feel way smoother than my single clutch ones. One of my biggest problem is the fact that our CR-V has very oddly spaced petals, so foot positioning can be a tad strange unless you plan ahead.

I've seen Tristan say in a thread somewhere that double clutching is pointless nowadays I've always wondered what the point in it was/is. I've tried it and I honestly can't feel a difference. Maybe I'm doing it wrong, I don't know, or maybe it's only useful in a certain type of car. I hardly know the first thing about engines so I have no idea what's going on inside of the engine when you're shifting, either

Considering how hard it is to do it (close to) perfect every single time and how well, fast and reliable synchromeshed transmissions work... Yeah, it pretty much is
Assuming we're talking about road cars of course.

Quote from morpha :

Considering how hard it is to do it (close to) perfect every single time and how well, fast and reliable synchromeshed transmissions work... Yeah, it pretty much is
Assuming we're talking about road cars of course.

Thats kind of what I figured, but I will say that I've just gone out and tried it on some twisty back roads, and it is quite smoother, but way slower. You shouldnt be using your engine for braking that much anyways, so you might as well go with what is fun/smoother.

Quote from speed1 :

You shouldnt be using your engine for braking that much anyways

Why not? Coasting saves fuel, ideally you burn exactly none (also resulting in no emissions btw, none at all) while braking.
Use your engine whenever possible! Whether it's moving due to internal combustion or external forces makes (almost) no difference to the drivetrain and engine internals, whereas regular braking will needlessly burn fuel and wear your pads and discs.

Whats wrong with simply heeling and toeing, it does the same job does it not?

i pretty much have to double de-clutch to get into 1st or 2nd from higher up, but thats just because my gearbox is shagged. Heel and toe braking i do quite often though, purely because it gives a smoother ride, and my size 14 feet are big enough to do it effortlessly. My Father used to double de-clutch in normal driving, purely because for a good majority of his driving life you actually had to.

Quote from morpha :

Why not? Coasting saves fuel, ideally you burn exactly none (also resulting in no emissions btw, none at all) while braking.
Use your engine whenever possible! Whether it's moving due to internal combustion or external forces makes (almost) no difference to the drivetrain and engine internals, whereas regular braking will needlessly burn fuel and wear your pads and discs.

I'm not talking about slowing going down hills or over mountain passes or in normal driving (and I know that when I see a light go to red in front of me, I put it in fourth and coast with the clutch engaged right up until the motor sounds like it hits 1500rpm because, yes, with a fuel injected engine that is way more efficient). What I'm talking about is the people who through it from 5th to 3 at 65 mph without blipping. That slows you down a lot faster than blipping, but it is super bad for the clutch. What I was getting at is that its better to use your brakes for the same amount of slowing force you'd get from relying on your clutch. Bottom line, I've spent a good deal of time driving over passes out in the rockies, so by no means am I anti-keeping-your-speed-under-control, but I am anti clutch reliant engine braking.

Double clutching is a technique that was once mandatory but nowadays it's outdated and useless with modern synchronizers.
Unless you drive a car with an ancient gearbox, you can let the synchros do the work.

The reason it's known wide-spread is either from older friends or family members... or just because it makes you sound really cool if you say "I always double clutch revmatch while downshifting".

Rev matching is a whole another story though. That's a matter of saving the clutch.

Quote from Wikipedia :

A double clutch (also called a double declutch) is a driving procedure primarily used for vehicles with an unsynchronized manual transmission.

Quote from (SaM) :

The reason it's known wide-spread is either from older friends or family members... or just because it makes you sound really cool if you say "I always double clutch revmatch while downshifting".

agreed

Quote from (SaM) :

Rev matching is a whole another story though. That's a matter of saving the clutch.

extra points for perfect clutchless shift which puts even less strain on the drivetrain as everything is perfectly aligned for the duration of the shift. zero clutch wear zero synchro wear... (not that they wear down significantly under normal, or even harsh, use)

Quote from dougie-lampkin :

Actually, I've taken to clutchless shifting recently. I've found at about 5k in every gear bar first, I can shift up clutchless with zero resistance, which I've been told means everything is syncro'd at that speed. I haven't noticed any strange noises or feel when driving, and I've also been told it lessens the wear on the syncros, as long as you have the revs matched. How accurate that is, I don't know

You won't know you're DD'ing correctly until you drive a car that has no synchromesh.

So I'm correct in assuming that the general idea is that its pointless with modern cars, but way more fun?

Quote from speed1 :

So I'm correct in assuming that the general idea is that its pointless with modern cars, but way more fun?

If kicking stuff with your left foot hundreds of times is your idea of fun, then yes.
I'll keep my dog away from you though.. he's kind of small and likes legs. Alot.

Quote from george_tsiros :

extra points for perfect clutchless shift which puts even less strain on the drivetrain as everything is perfectly aligned for the duration of the shift. zero clutch wear zero synchro wear... (not that they wear down significantly under normal, or even harsh, use)

Did you know that clutchless shifting actually works in LFS?

Quote from 5haz :

Whats wrong with simply heeling and toeing, it does the same job does it not?

No.

(Explanations below are grossly over-simplified. Be nice if you're going to nit-pick. )

Double-declutching (or double-clutching, depending on which country you live in), is supposed to match the speed of the drive shaft to the speed of the gear you are going to be engaging.

Heel-toeing performs a different purpose: to match the speed of the of the clutch plate linked to the engine, to the new speed of the clutch plate linked to the gearbox after a new gear is selected, as quickly as possible.

DD'ing helps to smoothly engage each gear to the collar, which is connected to the drive shaft. If the collar does not engage a gear properly (either due to a faulty synchromesh in a car so equipped, or due to lack of proper DD technique in non-synchromeshed cars), then you get "grinding" of the gears.

Heel-toeing helps to smoothly engage the clutch for each gear shift, preventing unnecessary clutch wear, and also helping to relieve some pressure from gearbox itself as a result. It also helps to maintain the balance of the car as optimally as possible, and prevent power-induced skids.

Note, however, that you DO NOT NEED to heel-toe, under any circumstance apart from racing. In normal road driving, or even in police pursuits or anti-ambush driving, the best practice is to performing braking and gear changing as separate actions.

Quote from (SaM) :

Did you know that clutchless shifting actually works in LFS?

yeah
no strain if you don't hit it exactly. no grinding noises or destroyed gearbox

Quote from samjh :

Note, however, that you DO NOT NEED to heel-toe, under any circumstance apart from racing. In normal road driving, or even in police pursuits or anti-ambush driving, the best practice is to performing braking and gear changing as separate actions.

This isn't true, I use heel and toe when dropping two gears at once, for example heading into a roundabout, shifting from 5th to 3rd. Just stamping on the breaks, and shifting into 3rd at high revs unsettles many cars - heel and toe here keeps the car from lurching forwards - some people are happy with blipping the throttle too or left foot breaking, which achieves the same things, but it's not as quick imo.

Quote from dawguk :

This isn't true, I use heel and toe when dropping two gears at once, for example heading into a roundabout, shifting from 5th to 3rd. Just stamping on the breaks, and shifting into 3rd at high revs unsettles many cars - heel and toe here keeps the car from lurching forwards - some people are happy with blipping the throttle too or left foot breaking, which achieves the same things, but it's not as quick imo.

You're obviously going way too fast on public roads if you employ heel toe braking for the sake of car balance.

Either too fast, or in a car with soft / ****ed suspension. You decide

Quote from dawguk :

This isn't true, I use heel and toe when dropping two gears at once, for example heading into a roundabout, shifting from 5th to 3rd. Just stamping on the breaks, and shifting into 3rd at high revs unsettles many cars - heel and toe here keeps the car from lurching forwards - some people are happy with blipping the throttle too or left foot breaking, which achieves the same things, but it's not as quick imo.

Nope, it's still not necessary.

If you need to heel-toe in order to maintain the balance of the car, you're heading into the roundabout too fast. Your braking should be completed before doing the gear change:

1. Brake to reduce speed. Brake to stop, but look for an opportunity to go.
   
2. If you are clear to enter the roundabout, you first make sure you're not travelling too fast to negotiate the roundabout.
   
3. Then your right foot should move to the accelerator to match revs, while your left foot operates the clutch, so that gear changing is done smoothly without upsetting the balance of the car.
   

For this to succeed, timing is critical. Your braking should be done well in advance so that you have the time to assess the traffic conditions into the roundabout (and determine whether you must stop, or whether it is safe to continue), and create enough time to perform the appropriate gear change at a safe and smooth pace. Also important is the smoothness of the application and release of the brake and accelerator pedals, again for maintaining good balance.

And it's not slow either. When done correctly, your entry speed will be well within safe pace, and you'll be on the throttle at or even before turning in. It's certainly not the FASTEST way (that will be using trail-braking and heel-toe, racing style), but the road is not as predictable or sterile as a race track. Margin of safety needs to be greater, and the slower entry speed is the price one pays for that safety.

Quote from samjh :

Nope,...

My point exactly.

Dawguk: don't be cool, be safe.

Quote from (SaM) :

My point exactly.

Dawguk: don't be cool, be safe.

On public roads, that's the same thing. To intelligent people anyways.

Quote from dawguk :

shifting into 3rd at high revs unsettles many cars - heel and toe here keeps the car from lurching forwards -

what?

what car would do that when going from 5th to 3rd and braking?

also, quit applying racing techniques on public roads. it's not appropriate. if your suspension is so much ****ed then it would be better if you went and, you know, fixed the damn thing... not "downshift from 5th to 3rd".