manual tranny myth #2

Driver Joined: Sep 25, 2006 Posts: 107

myth:
to learn how to drive your car like a race car, you need to learn how to 'race shift' or 'double clutch'

truth:
your car isn't a race car Very Happy

there isn't any need to shift differently

extra:
double clutching will save wear and tear on the bits in your transmission that make the gears match up but its a LOT of extra work for an extra couple years of life out of your transmission.

Posted: Tue Sep 26, 2006 10:07 pm

Not sure about a couple of years. A couple of days or may be weeks sound more realistic for me Smile

I never drove a real race car, but I used this technic on a small truck which did not have syncros. This was like 30 years ago Wink

I did not have any use for it ever since.
And, for racing, it seems to me it actually can have any sence only for downshifting - which is not employed in the favorite teen drivers passtime - street drag racing Smile

Driver Joined: Sep 25, 2006 Posts: 107

Nobody has ever been stupid enough to let me drive NASCAR and nobody ever will, but from what I hear, those cars don't have syncros because it saps a tiny fraction of the engine power to spin them so the driver double clutches and has more HP at the wheel

Member Joined: Nov 15, 2006 Posts: 18

Main reason for no synchrons is weight saving, partially to remove some rotating mass, but mostly for weight.
Double clutching is very useful for downshifting, as it provides less wear on transmission parts, and is safer and smoother. If the car has a 2 way LSD (limited slip differential), then by not double clutching on a downshift, you will lock up the drive wheels togather, which might cause you to lose control of the car.
A proper way to up-shift is not to yank the car through gear as fast as possible, but rather to have the shift timed exactly for the engine speed to be in balanced with the vihicle speed, then it will be nice and smooth, and smooth driving is proper driving.

Posted: Thu Nov 16, 2006 1:23 am

Pavlo wrote:

If the car has a 2 way LSD (limited slip differential), then by not double clutching on a downshift, you will lock up the drive wheels togather, which might cause you to lose control of the car.

You generally want to avoid shifting if you can lose control. Unless it's absolutely necessary.

Member Joined: Nov 15, 2006 Posts: 18

Yes, you are supposed to be fully in gear before the turn, but if say it is regular driver, who just got a new civic Si with a factory LSD, thinking it is something that will just give you more traction, will most likely shift during a turn. So if you are comming out of a long turn, and for any reason want to downshift, in most cases it will actually be safer to just let the car roll, so that you don't upset the LSD. But this is kind of getting off topic.
I always downshift, knowing it is not the best thing to do, but it is just a habbit that I can't control.

Driver Joined: Sep 25, 2006 Posts: 107

Wouldn't the LSD kick in on a downshift whether or not you double clutched?

Member Joined: Nov 15, 2006 Posts: 18

It will ne "locking up " a bit, but not much thought when you let go of the throttle, but when you downshift without double clutching, for a fraction of a second the differential will become almost fully locked up.

Posted: Sun Oct 05, 2008 5:58 pm

I have a problem with my 2004 Mazda 3, which I bought new. On all the other cars I've had, I could easily do heal-toe downshifting, but I can't do it with this car. I'm still thinking about having the accelerator extended downward so that I can execute heal-toe downshifts. Without being able to do so, I find it very awkward when I have to slow down to make turns at intersections.

Has anyone else had an accelerator modified to expedite heal-toe downshifts?

Posted: Mon Oct 06, 2008 12:30 am

Not sure why at all you need to use heel-and-toe in regular driving, and definitely never modified accelerator pedal for that - so can't really help here, sorry.

Posted: Mon Oct 06, 2008 1:09 pm

Of course one need not use heal-toe. That is not the point. Many people need not drive either. The question is not whether it is necessary; it is not necessary. The question is whether it is desirable, and I believe that it is desirable.

The point is that using heal-toe downshifting makes for a more fluid operation and saves time. The alternatives work less well.

If a turn requires slowing down enough to make a downshift necessary, there are several ways to do it. One way is to downshift while the right foot is on the brakes and drag the engine up to speed with the clutch. That increases clutch wear. Another possibility is to downshift before slowing down and match the engine speed to the car speed by blipping the accelerator, then applying the brakes. That requires downshifting at a higher speed and revving the engine higher than would be required if one slowed down before downshifting. Another possibility is to release the brakes considerably before beginning the turn, then execute the downshift. That wastes time because it takes a second or so to complete the downshift, during which time the car is coasting. Another possibility is to downshift after the turn, but again that is awkward and wastes time.

The heal-toe method is smooth, causes no extra wear to the clutch, and avoids wasting time. It makes it possible to execute a smooth downshift just before entering the turn without first releasing the brakes. When one enters the turn, the downshift has already been compelted and the clutch is engaged, so there is no need to fiddle with the transmission while executing or exiting the turn. The only disadvantage is that it requires practice to acquire the skill necessary to do it well.

Posted: Mon Oct 06, 2008 10:48 pm

Well, I'm afraid one will make more damage to the clutch learning to use this method than one ever could prevent Smile

But I really don't care if you use it or not, so I shouldn't probably even mention it in the first place Smile

Posted: Mon Oct 06, 2008 11:46 pm

I'm sure that some people would be incapable of learning heal-toe downshifting, and others wouldn't want to make the effort. But not getting it exactly right ocassionally would not do enough damage to matter. I've known people to drag the engine up to speed with the clutch after downshifting, and it takes a long time for the resulting excessive clutch wear to show up.

According to my late father, when he learned to drive (before 1920), it was the usual practice to teach learning drivers the mechanical details of the car and how it worked. The theory, which I think was probably correct, was that people could learn more effectively if they knew exactly what the clutch and gearbox did and how the engine worked. Many drivers now have absolutely no idea how the mechanism works and I think that that impares their ability to drive properly.

Posted: Tue Oct 07, 2008 3:23 pm

Yeah, they did this in Russia, too - I think at least till mid 90s. And then stopped, and I agree, such an approach produces driving crowd that have no clue of what they are doing Sad

Driver Joined: Dec 25, 2009 Posts: 100

Double clutching should be avoided in commercial cars as its surely damages the transmission and wears out soon, so its economically not appreciable to do double clutching and shifting.