Not exactly.

Double clutching is used to match the tranny input shaft speed to the gear speed in the tranny so that when you shift into gear the gear speeds are the same otherwise you wouldn't be able to get it into gear. This is what synchronizers do. It is absolutely useless in a car with synchronizers unless yours are bad. The only thing it will do is save some wear on your synchronizers. It won't make you downshift faster. It will make you downshift slower due to the extra step. Rev matching on a downshift using heel toe is NOT double clutching. Double clutching was the technique you had to use before synchros. It is worthless today and serves no purpose other than to make you shift more slowly and introduce more steps for error. Not something you want coming into a corner hot especially when it isn't necessary.

Example: Third gear to second gear downshift in a 1975 Mack Truck. (Best example I could think of) Imagine a 1927 Ford if you want.

In third gear = Engine and 3rd gear are at the same speed.

Push in clutch = input shaft is at 3rd gear speed

Shift into neutral = input shaft is coasting down

Let out clutch = input shaft matches engine speed

Blip throttle = Engine and input shaft speed rise to the RPMs you blipped up to. Should be close to what 2nd gear will be. Closer it is the smoother the shift will be. Ideally it should be a tad bit higher.

Push in clutch = input shaft is coasting down

shift into Second = input shaft has coasted down to exactly Second gear speed

Let out clutch = tranny is in second gear

 

Read this and never speak of double clutching again on a performance car board unless your ride has 18 gears. F'u vin diesel.
http://en.wikipedia.org/wiki/Double_clutch

 

b-spot......regarding the downshift and double clutching......exactly how my old man taught me to do it years ago. Easier on the clutch and gears.

freakaccident.....right on the money with your information.


Being a past truck driver we actually never clutched past 1st gear, only relied on our RPM's to get to next gear. Downshifting was always double clutching.
New vehicles and short shifters do not require any of the old school methods. Just results in gear an clutch problems.

 

When i'm 107, I'll still be rowing through the gears, banging them out, powershifting, shifting without a clutch, doing massive burnouts, drifting around corners at high speeds.....you get the point

 

can't put it any better than that. If I'm in a rush to downshift and I know my RPMs are going to be high coming out I'll rev match. If I'm in no particular hurry and I know I'm not going to come out after my downshift above ~3200RPM I'll just slip it out. I know people that have done this for years every time they downshift and never once have they had to replace a clutch even on vehicles that are more than 10 years old.

But you're correct to reduce clutch wear as much as possible rev matching on a downshift is the best path to take. I'm just honestly too damn lazy and almost never in that much of a hurry to get to a lowest gear. On occasion I'll just hold the throttle where it will match and downshift and hope to god I'm not off otherwise refer back to point 3 .

 

I only break in second and allways match my rpm at 3000 when downshiffting. Car seems to respond very wqell and stops on a dime.

 

Yes exactly. Rev matching with your car in neutral and the clutch out (EXACTLY what I said above) matches engine speed to transmission speed. This means you have ZERO clutch wear as your flywheel and clutch are spinning at the same speed when you let the clutch out.

I suppose the fastest way to downshift without throwing yourself through your windshield would be to rev match mid shift with the clutch in. This wears on your throwout bearing though, which is why I don't do it. I can double clutch just marginally slower than this anyways, as I'm very used to it by now.

No its not necessary, but I baby my clutch when I'm not launching hard. I want it to last as long as I can.

 

Ok I drive a truck for a living nad will explain "Dubble Clutching" for you.

This is a shifing methid used on transmisons with NONsynchronized gears like the ones in my truck. (A Cobalt and all other pessenger cars made today for that mater have synchronized gears)
First to move you put the clutch all the way to the floor. (this engages the clutch brake and lets you in to gear)
On a nonsynchronized trans this is the only way to get the thing in gear without messing things up realy bad.
Next releas the clutch like you would in a car and THEN give it fuel.
Now to change gears you will now dubble clutch.
First push the clutch in about 1/4 of the way, then move the shifter to nutral.
Then relese the clutch, then push it in in about 1/4 of the way and move the gear shifter to the next gear. Now releas the clutch.
In my truck you would then repeat this proses 8 more times to be in top gear.

Now in your car this is pointless. In my truck it must be done to change gears. There is one other way to change the gears in my truck but we wont go in to that. Lets just say after Im moveing I dont use the clutch any more.

Now on to granny shifting.
This is most comanly known as shifting befor red line and doing it slowly.
Shifting like you normaly would in every day driving but at a higher RPM while racing or just trying to go realy fast is granny shifting.

Hope this helps some one.
Sorry for the long post...lol

Later

 

Hmmm....where i come from Granny Shifting isn't shifting slowly....it's riding the clutch inbetween shifts.

 

It may reduce clutch wear but it in no way reduces it to zero. Pretty nice theory but it's impossible to match the speeds exactly.

If you think that rev matching without double clutching is gonna wear your throwout bearing out before your disc or PP then go ahead and waste all that time clutching. You need to hit the autox and see how long that lasts.

 

When racing atuo x, I don't care about saving my clutch. I save it for days like those, and don't waste time double clutching.

On the highway though if I'm in 5th and need to downshift to 3rd or 4th to pass, thats my prefered method.

 

cool info and I now understand it pretty good. The way it was explained to me in the past was obviously wrong compared to all the other posts but im glad I know whats up.