DC350

I've heard alot on "double clutching" i have my versions of it in my head. Could anyone Please tell me what it is? Thanks.....Oh and the clutch goes in my rex today, tranny hopefully to

Anyone have rims forsale????? pm me

'Vert in Vegas

It is a race car drivers technique.
While shifting gears;
1 Let the clutch out while the shifter is in neutral
2 Depress clutch again
3 Then complete your shift.
That is "double clutching"
The purpose is to let the gears accelerate and match engine speed for a smoother shift,
AND
less wear and strain on your gearbox.

dre_2ooo

Only Riceboys double clutch

********THIS IS NOT A RACING TECHNIQUE!********


here it is : you're driving @ 25 mph in 2nd gear and you wann shift to 3rd. Push the clutch in and put the shifter in N. Let the clutch out. Push the clutch in again and put the shifter into 3rd. Release the clutch.

OBVIOUSLY this is a VERY slow way to shift. They used to do it back in the day when trannys weren't as good. NOW you have SYNCHROS in your car. They're made so that you can just shift without doing all that BS.

RX7GT

Be thankful that double-clutching is not necessary in everyday driving, especially in traffic. I know my left leg gets enough work just pushing in once per shift, imagine twice the effort! The technique evolved from large trucks and semis from as far back as the beginning of the automobile. Most truck drivers today still double-clutch their rigs just because of the design of the gears in the transmission. If you have ever seen the shape of the gears in a passenger car's trans, you would notice that the splines are set at an angle. This helps reduce noice and effort when shifting. However, if you look at a Peterbilt's gears you would see that the splines don't have the angle. btw: alot of purpose-built racecars (I saw this on NASCAR TODAY) use the straight gears due to strength but don't have to worry about the noise of the gears because....well, it's a racecar. Most passenger car owners don't want to hear gear noise while driving plus they want an easier shift, hence the angled splines and the lack of double-clutching. Yes, you will get less strain and wear on your gearbox but the difference is will be very minimal in everyday driving unless you drive really hard and slam the shifter between gears. This concludes today's history lesson. ---Jeremy

btw: if you really want to learn where the gears line up at which RPM, try shifting without using the clutch. It is possible to shift in and out of gears easily without engaging the clutch by using engine speed. For example, if you are upshifting from 2-3, get to a steady speed and lightly pull the shifter out of gear while keeping the R's EXACTLY the same. Once you hit neutral, lower the R's slightly and gently push the shifter toward 3rd. It should drop into gear easily once you have lined up the synchros by using engine speed. CAUTION: this will cause wear and grinding of the gears and I do not recommend you use this technique more than once or twice. However, it has helped me in a couple of cases when my clutch has gone out while driving. I was able to slow the vehicle by downshifting without using the clutch. Learn the technique but keep it in the back of your head for an emergency.

DC350

okay, yeah, thats what i thought it was just not sure

Icemark

Man you guys are forgetting the most important part of double clutching: the gas. You need to blip the gas while it is in neutral to bring up the RPMS to what you are expecting to let the clutch out at.

the clutch in, neutral, clutch out, clutch in, select gear clutch out, method that most of you described so far is not double clutching... it is dual clutching and just a waste of time.

Silkworm

What?

Yes, it's a racing technique. It certainly isn't something that most of us do on the street, and it has ZERO application for drag racers. All you silly boys who think in straight lines..

The idea is, without syncros, you have to match the transmission speed to the crankshaft speed. You know all those threads about straight cut gears and dogtooth transmissions? Exactly, those guys have to do this. Those transmissions are way stronger than tthe street trannys in our cars, but you pay for it with noise, and having to doubleclutch all the time

As said earlier, to do this, it's on the downshift, clutch in, put the transmission into neutral, clutch out. Blip the gas, clutch in, put the transmission into the next lower gear, and clutch out. Hence, doubleclutching. keeps the back of the car from being shocked by the wheels having to power the engine to keep up with the lower gearing. Not be a big deal on the street, but when you're on the fine edge of locking up the brakes, coming into turn 3, ANYTHING that upsets the car is a bad bad thing.

Also somewhat known as rev matching or heel/toe. Personally, I prefer the clutch in, put into the next lower gear, rev (more than a doubleclutch), and clutch out. I'm not all that coordinated yet

Cya

PaulC

NZConvertible

Huh? Heel/toe and double clutching are two completely different things! You only use the clutch once when using the heel/toe method. If you have a synchromesh gearbox, you don't need to double clutch, it's a waste of time. Heel/toe is a smoother (not quicker) way to downchange at high revs.

dre_2ooo

Exactly

Silkworm

Ok, look. 99.9995% of these guys will NEVER IN THEIR ENTIRE LIFE, drive a vehicle without a syncro style gearbox.

If you want to get ABSOLUTELY nitpicky, then yes, you are sorta correct. In a syncro car, you only need to get the revs up to match the drivetrain, the syncros will handle getting the input and output shafts up to speed.

With doubleclutching, you're letting the car rev the transmission up in neutral to match the input shaft with the output shaft speed, before selecting the next gear.

However, BOTH METHODS use heel toe, that's simply a description of using your right foot to simulatenously use the brake, while blipping the clutch.

Are you absolutely happy now, with these lengthy description?



Oh, and Dre, you can just sit down, you said originally that it wasn't even a racing technique. Exactly my ***.

PaulC

Scott 89t2

heel toe IS double clutching, with the addition of braking at the same time. so it's the same... it just alows you to double clutch down shift while on the brakes. using all 3 pedals at once.

NZConvertible

I've been using the heel/toe method when down changing for years, and I've never pushed the clutch in more than once per gear change. I've also been passengered in quite a few racecars (with synchro 'boxes) and never seen those drivers do it either. Talk to a race driver; when they talk about heel/toe, they're not referring to double clutching.

Scott 89t2

but if you are only using the clutch once. then you are not rev matching. therefore not using the gas pedal. so you are at the most using 2 pedals. and you have 2 feet. why would you heel toe??... heel toe is so you can use 2 pedals at once with one foot.

NZConvertible

OK, I do it like this:

- approaching corner, commence braking by pushing on the pedal with the ball (the bit behind you toes) of your right foot
- when required, push clutch in with your left foot
- start to change gear
- while still braking, swing the heel of your right foot over the accelerator and blip it, raising the revs (this bit takes heaps of practice to perfect)
- slip shifter into lower gear
- release clutch

Three pedals, two feet, one clutch actuation and a nice smooth gearchange that doesn't compression lock the rear wheels charging through a fast right hand hairpin, sending you off the track backwards...

gotorx7

True! But the two pedals are the BRAKE and the ACCELERATOR... the clutch doesn't get a mention

momar

I've always heel-toed using one clutch engagement. From my understanding, heel-toe is used to be in the correct RPM for the speed in a lower gear,while double clutching is used to have a smoother shift.

Scott 89t2

hmm I always though rev matching without douple clutching was usless. cause the tranny and gears ect are not matched while reving in "N". just the engine rpm. but I guess now that I think that would stop the lock up, but just not make the shift any smother.

why wouldn't you double clutch? to hard at once? I aways thought you did while heel/toeing.

DoriZaru

First of all, double-clutching has nothing to do with the pitch of the gear teeth in a transmission. I don't care if they're straight-cut or hypoid, they never come disengaged from each other. A basic understanding of how a constant-mesh gearbox works would go a long way here.

Double-clutching is exactly what the name indicates: disengaging and re-engaging the clutch twice for one change of gear. You can do it changing up or down. The idea is that by re-engaging the clutch in neutral and blipping the throttle, you are actually spinning the guts of the tranny up to the RPMs that they will need to be at to engage the next gear seamlessly, as opposed to bringing up only the engine's RPMs. Heel and toe has nothing to do with it, unless you're trying to blip the throttle on the downshift while braking. Incidentally, the name heel and toe is from the bygone day when the throttle pedal was in the middle on some race cars with the clutch and brake arrayed to either side.
As with most things, double-clutching is used by some, not by others- there is no complete consensus as to whether or not it is a useful technique anymore, and the discussion is basically a moot point with the advent of clutchless and semi-automatic transmissions in most of the top levels of racing. Bottom line? It's pointless in a street car, and doubly so if you're drag racing. Learning to heel-toe, however, is quite handy. So is learning to left-foot-brake and downshift without using the clutch (it can be done without making crunching noises if you learn to do it with finesse).

#1 Mod you can do to improve the performance of your car? Driver upgrade. Do a racing school- you will not regret it.

Felix Wankel

Takes too long. You need it in gear ASAP to get out of the corner. Double clutching a synchro trans is basically pointless unless you're trying to baby the trans or if the synchros are already crunchy.

NZConvertible

There’s an excellent article on how manual gearboxes work at How Stuff Works That’s the only reason I use it. Why else would you bother? Yeah, but since you still use your heel and your toe... The discussion is quite relevant here, since we all still have quite conventional transmissions. Absolutely; not only is it useful on the track (my example above!), it’s useful and fun during any serious cornering while out having a good fang on some windy back roads!

The Ace

Everyone here seems to be forgeting that heel-toe may be useful for producing weight transfer effect to de-stabilize the car coming up on a turn, in order to position the car to take the turn as fast as possible... .......or to produce the known "flick", using the throttle on RWD or the handbrake in FWD cars

NZConvertible

How does a smooth downchange destabilise the weight distribution during cornering? Just curious...

The Ace

No, its not the smooth one, its the abrupt one
You dont heel-toe to rev the engine to rev-match, but after you go down a gear (or two), you must rev the engine to throw out the rear (in RWD), or to get the front wheels spinning so that they can start pulling the car towards the exit of the turn as soon as the handbraking is over...

You have to heel-toe because, frankly, you dont have time to do this in seperate moves