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[question] double clutch

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Old Mar 12, 2004 | 04:29 PM
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Question [question] double clutch

I acutually have two questions.

1) I know when we double clutch, we have to:
- clutch in
- shift to neutral
- release clutch
- rev up (rev match)
- clutch in
- downshift
- release clutch and gas

I am just wondering why do we need to shift to neutral to rev. I mean if clutch in = neutral, then why can't we just simplify the steps to:
- clutch in
- downshift
- rev up (rev match)
- release clutch and gas

2) I've read many post about good/bad driver will determine how fast the car run (in a straight road), but what do you consider as a good driver? shift faster and smoother? shift at right rmp? I always got confused about this... I always thought that everyone do drive manual very similiar in a straight road

Thanks for your help
Old Mar 12, 2004 | 05:03 PM
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you don't need to shift into neutral, if you're just trying to rev match, you can do that when the clutch is engaged, then shift.
Old Mar 12, 2004 | 05:04 PM
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Double clutching is more necessary when the transmission doesn't have any synchros. Normally the synchro would bring the gears up to the proper speed on a downshift. Without them you have to use the engine to do it.

By putting the car in neutral you disconnect the transmission from the rest of the drivetrain. By letting the clutch out you connect the engine to the transmission. The rev up brings the gears to the higher speed.

Pushing the clutch in disconnects the engine from the transmission. Shifting connects the transmission to the rest of the drivetrain. Clutch in connect the engine back up.

So a simple rev match helps ease the shock on the clutch. A double clutch eases the work your synchros have to do, or does their job if you don't have them.
Old Mar 13, 2004 | 03:44 AM
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I see I see, thank you for your answer.

I just got my first manual car recently, still have alot to learn, but so far, I think manual is alot more fun than auto

thank you again
Old Mar 13, 2004 | 04:40 AM
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Double clutching has a huge effect on synchro life. Had an 85 Mustang GT and blew the synchros in 70K miles before I heard about double clutching. Had an 88 GT with 160 miles with original clutch and synchros with no problems before I traded car with double clutching.

(Or you could always use the brakes - they're usually cheaper to replace than breaking into the tranny - but not as much fun as double clutching)
Old Mar 14, 2004 | 12:37 AM
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yea, that's what I've heard too. haha, I think I did enough damage to my clutch during the past two months already (shouldn't have use a new car to learn how to drive manual...)
That's why I want to learn all the technique that can possibly make my car more durable.

can you explain to me how to use the brakes instead of double clutching?

thanks
Old Mar 14, 2004 | 12:43 AM
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yep, it's an old technique which really isnt needed as much today. like someone before me said, it's for cars without synchros. basically, double clutching is for protecting your transmission. by rev matching during the double clutch technique, you're basically doing what the synchro's now would do.
Old Mar 14, 2004 | 01:30 AM
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So should I start double clutching to save my synchros at the race track, since there's usually a larger rpm jump than on the street? Or will the difference be nominal since I only drive on the track about 1% of all my driving?
Old Mar 14, 2004 | 04:49 AM
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Re: your question, "can you explain to me how to use the brakes instead of double clutching?"

Don't use the transmission to slow the car down. Double clutching is cool, but it's a "heel-toe thing" done properly - should be done with your right heel on the brake, and your right toes on the gas.

So, as you are slowing to downshift, it's . . .

1. right heel on the brake to slow the car
2. left foot on the clutch
3. car into neutral
4. left foot off the clutch
4. right toes on the gas (get the revs up a bit)
5. left foot on the clutch
6. drop to lower gear
7. left foot off the clutch
8. right toes on the gas and go!

All the time, your right heel is still contacting the brake pad. Do not ride the breaks though, use them only to slow down the car to the speed you want to be at when you hit the gas.

It takes some practice (like normal shifting) but after a while it comes naturally without thought.

Good luck!
Old Mar 14, 2004 | 05:54 AM
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whoa redcat you have an interesting way of doing heel-toe. because i believe most people use their right toes to brake and their right heel for the throttle
Old Mar 14, 2004 | 06:06 AM
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I'm sure either will work. I guess it's just whatever you're comfortable with.
Old Mar 14, 2004 | 11:54 AM
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you must have real flexible hips.

The ball of my foot is always on the brakes, not the gas, for control.
Old Mar 14, 2004 | 12:40 PM
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We had a discussion about whether the heel went on the brake of the toe. According to the SCCA articles I've seen, the heel brakes and the toe does the gas, as you want to have a fairly steady pressure on the brake and a controlled amount of pressure on the gas. But I've seen online articles showing the opposite. What I find for myself is that I can not get my heel all the way on the gas pedal while pushing the clutch in, so I'll go with the heel on the brake and feather the gas. I am still far from getting this trick down enough to try in a racing situation though.
Old Mar 14, 2004 | 03:15 PM
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Originally posted by redcat
Re: your question, "can you explain to me how to use the brakes instead of double clutching?"

Don't use the transmission to slow the car down. Double clutching is cool, but it's a "heel-toe thing" done properly - should be done with your right heel on the brake, and your right toes on the gas.
I see I see, learn something new everyday

heel-toe and LFB is what I'm planning to learn after double clutching. Even though I have 4 years of driving experience (automatic), but I feel like a new student driver again when I'm driving manual now.

Thank you for your detail explaination, it really did help alot
Old Mar 14, 2004 | 03:27 PM
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I've heard that Raillart has 3 level of synchros at 2nd gear (again, i'm a newbie of manual, so shoot me if i'm wrong )

In order to use the synchros when downshifting (without rev match), do I just have to let the clutch out more slowly and let the system do its job?

So does that also means that I can let the clutch out quicker if I rev match?

Thanks


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