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      02-07-2008, 07:45 PM   #111
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^^ makes the experience 10 times funner once you get it down
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      02-07-2008, 07:50 PM   #112
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Quote:
Originally Posted by mantis View Post
^^ makes the experience 10 times funner once you get it down
Yea it was fun- it's just that I have think about it now and it's work- it'll be alot more fun when it's second nature I'm sure...
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      02-07-2008, 08:00 PM   #113
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Quote:
Originally Posted by BoostedBMW View Post
I've only skimmed the first few posts because I have been driving a MT for a few years and don't think I need to learn at this point, but why would you need to push in the clutch twice to revmatch a downshift? That just seems like it would take waaaaay to long to do smoothly.

Just put the clutch in, select the lower gear, and as you are letting the clutch back out blip the throttle right before the engagement point. I guess I don't see the point of double clutching then.
It is important to match revs on a downshift. If you do not match revs when you engage the lower gear the car will slow down. This will transfer weight to the front wheels, enlarge the size of the front contact patches and reduce the size of the rear contact patches. If you are at or near the limits of adhesion this can cause Trailing Clutch Oversteer (TCO) which can cause the car to spin out.

To properly execute a downshift while braking:
1. Apply the brakes smoothly with the left side of your right foot..
2. Depress the clutch with your left foot
3. While braking rock your right foot and "blip" the accelerator.
4; Shift into the next lower gear.
6. Release the clutch.

If this is done properly the car will not slow down/

On cars without synchomesh transmissions it is necessary to "Double Clutch"

1, Apply the brakes with the left side of your right foot.
2. Depress the Clutch with your left foot.
3. Shift into neutral
4. Release the Clutch
5.While still braking smoothly rock your right foot and "blip" the accelerator
8, Depress the clucth with your left foot.
9. Shift into the next lower gear.
10. Release the Clutch.

Once you get the hang of it this can be accomplished very quickly and very smoothly.

Many race cars have "Straight Cut" gears and non-synchomesh transmissions.

Most modern MT cars (such as BMWs) have bevel cut gears and sychomesh transmissions. Although "Double Clutching" will work it is not necessary.

I got into the habit of double clutching when I started learnig how to drive race cars. I had 130,000 miles on my Lexus SC300 when I got rid of it and I was still on the original clutch and brakes.


"Coasting" is not a good practice. To keep a car properly balanced you should either be accelerating or braking or applying "maintenance throttle". This is not usually citical whe driving on the road well below the limits of the car but when driving a race car at or close to the limits "coasting" can upset the cars balance. The brakes and accelerator are as much for keeping the car balanced as they are for speeding up and slowing it down.



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Last edited by captainaudio; 02-07-2008 at 08:29 PM.
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      02-07-2008, 08:33 PM   #114
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Q: On a HARD brake (not slamming the brakes), how many of you guys unintentionally leave your car in neutral because you have the clutch depressed, even though you have moved your shifter to the lower gear?

....just thought I'd start a new Q: in the spirit of the thread.

As I slow down, I usually downshift to go with it, but when I brake hard, I usually have the clutch depressed and end up in neutral. That's because when I brake hard, it's a natural feeling to keep both feet depressed in the same direction (left foot clutch, right foot brake). Your attention is also typically diverted by the traffic situation which caused you to brake hard in the first place.

Except for that, it's all good. I had put 95K miles on my Prelude on my original clutch b4 I sold the car, and the clutch was still good. No slips at all, despite aggressive driving / downshifting, etc. Of course, that car didn't have much torque, so it was easier on the clutch, but still, 95K miles on the original clutch shows I didn't have too many bad shifting habits
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      02-07-2008, 09:01 PM   #115
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Quote:
Originally Posted by orionredwing View Post
Q: On a HARD brake (not slamming the brakes), how many of you guys unintentionally leave your car in neutral because you have the clutch depressed, even though you have moved your shifter to the lower gear?

....just thought I'd start a new Q: in the spirit of the thread.

As I slow down, I usually downshift to go with it, but when I brake hard, I usually have the clutch depressed and end up in neutral. That's because when I brake hard, it's a natural feeling to keep both feet depressed in the same direction (left foot clutch, right foot brake). Your attention is also typically diverted by the traffic situation which caused you to brake hard in the first place.

Except for that, it's all good. I had put 95K miles on my Prelude on my original clutch b4 I sold the car, and the clutch was still good. No slips at all, despite aggressive driving / downshifting, etc. Of course, that car didn't have much torque, so it was easier on the clutch, but still, 95K miles on the original clutch shows I didn't have too many bad shifting habits
You should never slam the brakes. The brakes should be squeezed. With practice you can learn to "threshold" brake (brake hard but still not lock the brakes). If this is done well you can outperform ABS. If you are turning while braking you will have to "give back" some brakes to allow the car to turn. At the exteme these techniques can be used to "rotate" the car and point it into a turn. The clutch should only be depressed when you are changing gears and then only for a very short time. You want to minimize the amount of time that the engine is not coupled to the drive wheels.

Skip Barber racing (www.skipbarber.com) has a book and a video called "Going Faster" that explains these techniques very clearly.

http://store.nexternal.com/shared/St...unt2=118369698
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      02-07-2008, 09:24 PM   #116
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Quote:
Originally Posted by mantis View Post
I found this article very helpful.

http://en.wikipedia.org/wiki/Clutch

Make sure you understand the functions of 3 things very well and ask questions if you dont:
1. What the clutch plate does
2. What the flywheel does
3. What the synchronizers do
Does anyone have a link that shows an actual photo of a synchronizer to help me understands how it works. The link above described the synchronizer but I am having a hard time applying the text description into pictures, a real photo would be a plus.
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      02-07-2008, 10:01 PM   #117
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Quote:
Originally Posted by joonsup View Post
the only time i roll in neutral is when my gas light has been on and i'm going downhill trying to find the closest gas station. haha. luckily i haven't had to do that with my bimmer yet.
Your car will get better mileage rolling downhill in 6th, than it gets rolling downhill in neutral.

This is why we need this thread.
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      02-07-2008, 10:06 PM   #118
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Quote:
Originally Posted by captainaudio View Post
It is important to match revs on a downshift. If you do not match revs when you engage the lower gear the car will slow down. This will transfer weight to the front wheels, enlarge the size of the front contact patches and reduce the size of the rear contact patches. If you are at or near the limits of adhesion this can cause Trailing Clutch Oversteer (TCO) which can cause the car to spin out.

To properly execute a downshift while braking:
1. Apply the brakes smoothly with the left side of your right foot..
2. Depress the clutch with your left foot
3. While braking rock your right foot and "blip" the accelerator.
4; Shift into the next lower gear.
6. Release the clutch.

If this is done properly the car will not slow down/

On cars without synchomesh transmissions it is necessary to "Double Clutch"

1, Apply the brakes with the left side of your right foot.
2. Depress the Clutch with your left foot.
3. Shift into neutral
4. Release the Clutch
5.While still braking smoothly rock your right foot and "blip" the accelerator
8, Depress the clucth with your left foot.
9. Shift into the next lower gear.
10. Release the Clutch.

Once you get the hang of it this can be accomplished very quickly and very smoothly.

Many race cars have "Straight Cut" gears and non-synchomesh transmissions.

Most modern MT cars (such as BMWs) have bevel cut gears and sychomesh transmissions. Although "Double Clutching" will work it is not necessary.

I got into the habit of double clutching when I started learnig how to drive race cars. I had 130,000 miles on my Lexus SC300 when I got rid of it and I was still on the original clutch and brakes.


"Coasting" is not a good practice. To keep a car properly balanced you should either be accelerating or braking or applying "maintenance throttle". This is not usually citical whe driving on the road well below the limits of the car but when driving a race car at or close to the limits "coasting" can upset the cars balance. The brakes and accelerator are as much for keeping the car balanced as they are for speeding up and slowing it down.



CA
BINGO ... finally
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      02-07-2008, 10:53 PM   #119
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+1

Note I also mentioned to not slam the brakes in my post.

Quote:
Originally Posted by captainaudio View Post
You should never slam the brakes. The brakes should be squeezed. With practice you can learn to "threshold" brake (brake hard but still not lock the brakes). If this is done well you can outperform ABS. If you are turning while braking you will have to "give back" some brakes to allow the car to turn. At the exteme these techniques can be used to "rotate" the car and point it into a turn. The clutch should only be depressed when you are changing gears and then only for a very short time. You want to minimize the amount of time that the engine is not coupled to the drive wheels.

Skip Barber racing (www.skipbarber.com) has a book and a video called "Going Faster" that explains these techniques very clearly.

http://store.nexternal.com/shared/St...unt2=118369698
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      02-08-2008, 01:06 AM   #120
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I have a question regarding going on an incline in traffic. Every morning I have to get on the freeway and the entrance ramp that allows 2 cars per green light is on an incline. I crawl up the ramp somewhat slipping/feathering the clutch and applying enough throttle to keep moving. I'll brake when i have to and keep the clutch in at the same time as its very brief before I start moving again. The whole time going up the ramp I do not fully engage the clutch. Is what Im doing incorrect?
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      02-08-2008, 03:08 AM   #121
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Quote:
Originally Posted by gos View Post
Your car will get better mileage rolling downhill in 6th, than it gets rolling downhill in neutral.

This is why we need this thread.

+1
Quote:
Originally Posted by jnizzle View Post
I have a question regarding going on an incline in traffic. Every morning I have to get on the freeway and the entrance ramp that allows 2 cars per green light is on an incline. I crawl up the ramp somewhat slipping/feathering the clutch and applying enough throttle to keep moving. I'll brake when i have to and keep the clutch in at the same time as its very brief before I start moving again. The whole time going up the ramp I do not fully engage the clutch. Is what Im doing incorrect?
yah that's bad for your clutch... that's like those who sit at traffic lights and keep going back and forth using the clutch (aka Mantis )
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      02-08-2008, 08:51 AM   #122
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Quote:
Originally Posted by txusa03 View Post
Does anyone have a link that shows an actual photo of a synchronizer to help me understands how it works. The link above described the synchronizer but I am having a hard time applying the text description into pictures, a real photo would be a plus.
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      02-08-2008, 09:54 AM   #123
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not a vid but check this out

http://auto.howstuffworks.com/transmission3.htm
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      02-08-2008, 10:05 AM   #124
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More on transmission mechanics:

http://auto.howstuffworks.com/framed...om/gearbox.htm
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      02-08-2008, 10:06 AM   #125
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this is a bit but i think it's good info

How To Read Gear Ratios

http://auto.howstuffworks.com/framed...80/TIP094.html
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      02-08-2008, 11:42 AM   #126
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I haven't looked at the photos linked above, but most synchros I've seen in photos are pretty unsophisticated. They look like brass rings. One side is fixed to the collar and the other is open and grabs the end of the spinning gear to synch up the speed of the collar to the gear, so the teeth of the collar will plug into the gear without grinding. Basically, it is grabbing the gear without teeth to allow it to slip a bit and speed up, before it inserts the teeth into the gear.

Those with more knowledge can correct me if I've described it wrong, but it seems like a brilliant but uncomplicated solution. I'd imagine synchros get hot quickly and will get worn if you do a lot of downshifting without rev-matching.
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      02-08-2008, 11:43 AM   #127
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OT, but why was this thread moved? Bogus decision on the part of the mods. People are not seeing it/responding as a result.
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      02-08-2008, 11:44 AM   #128
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yes it did move. it used to be in General talk, but now it's in performance/tracking, etc
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      02-08-2008, 11:45 AM   #129
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Quote:
Originally Posted by BK View Post
I haven't looked at the photos linked above, but most synchros I've seen in photos are pretty unsophisticated. They look like brass rings. One side is fixed to the collar and the other is open and grabs the end of the spinning gear to synch up the speed of the collar to the gear, so the teeth of the collar will plug into the gear without grinding. Basically, it is grabbing the gear without teeth to allow it to slip a bit and speed up, before it inserts the teeth into the gear.

Those with more knowledge can correct me if I've described it wrong, but it seems like a brilliant but uncomplicated solution. I'd imagine synchros get hot quickly and will get worn if you do a lot of downshifting without rev-matching.
that's what i thought. if you do not rev-match bliping at neutral you will wear out your synchros quick.
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      02-08-2008, 11:49 AM   #130
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I dont have sound, but i think this guy is discussing the synchro's at some point in his video

http://videos.howstuffworks.com/hows...work-video.htm
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      02-08-2008, 12:03 PM   #131
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Quote:
Originally Posted by captainaudio View Post
It is important to match revs on a downshift. If you do not match revs when you engage the lower gear the car will slow down. This will transfer weight to the front wheels, enlarge the size of the front contact patches and reduce the size of the rear contact patches. If you are at or near the limits of adhesion this can cause Trailing Clutch Oversteer (TCO) which can cause the car to spin out.

To properly execute a downshift while braking:
1. Apply the brakes smoothly with the left side of your right foot..
2. Depress the clutch with your left foot
3. While braking rock your right foot and "blip" the accelerator.
4; Shift into the next lower gear.
6. Release the clutch.

If this is done properly the car will not slow down/

On cars without synchomesh transmissions it is necessary to "Double Clutch"

1, Apply the brakes with the left side of your right foot.
2. Depress the Clutch with your left foot.
3. Shift into neutral
4. Release the Clutch
5.While still braking smoothly rock your right foot and "blip" the accelerator
8, Depress the clucth with your left foot.
9. Shift into the next lower gear.
10. Release the Clutch.

Once you get the hang of it this can be accomplished very quickly and very smoothly.

Many race cars have "Straight Cut" gears and non-synchomesh transmissions.

Most modern MT cars (such as BMWs) have bevel cut gears and sychomesh transmissions. Although "Double Clutching" will work it is not necessary.

I got into the habit of double clutching when I started learnig how to drive race cars. I had 130,000 miles on my Lexus SC300 when I got rid of it and I was still on the original clutch and brakes.


"Coasting" is not a good practice. To keep a car properly balanced you should either be accelerating or braking or applying "maintenance throttle". This is not usually citical whe driving on the road well below the limits of the car but when driving a race car at or close to the limits "coasting" can upset the cars balance. The brakes and accelerator are as much for keeping the car balanced as they are for speeding up and slowing it down.



CA
Very nice explanation. I'm not sure why it was directed at me since I revmatch everyday and heel/toe pretty often despite this gas pedal setup that I hate in this car, but that's a rant for another thread.

Ok, I guess I worded my other post wrong. I have always known why you need to revmatch. All you need to do is drive 100ft and downshift without doing so to realize this. What I don't get is why you need release the clutch when revmatching/downshifting. To me, this seems like a waste of time when you can just keep your foot down on the clutch, which is the same as being in neutral, and blip the throttle right before letting it back out. I just do it in a fluid motion. To have to release the clutch out to blip the throttle and then put it back in, just to release it once again seems like its redundant for no reason. Maybe I just have a different driving style, but when I downshift its smooth and quick so I guess I have to be doing something right. BTW, I'm not talking in theory here about a friend who told me how to drive a MT. I drive one everyday for the past several years so I understand what's going on between the engine and the drivetrain, but I just don't get the practice of actually hitting the clutch twice when you can get the same results in only doing so once. Does this make sense to anyone else?

*edit*... I just re-read your response about synchros versus a dogbox and I now realize what you are trying to say, which is exactly what I was thinking in that its not necessary to doubleclutch a street car. I thought I was going crazy for a minute.
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      02-08-2008, 12:07 PM   #132
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Quote:
Originally Posted by BoostedBMW View Post
Very nice explanation. I'm not sure why it was directed at me since I revmatch everyday and heel/toe pretty often despite this gas pedal setup that I hate in this car, but that's a rant for another thread.

... but I just don't get the practice of actually hitting the clutch twice when you can get the same results in only doing so once. Does this make sense to anyone else?
no one is doubting your driving skills in particular. his comment was general for all of us.

I think you double-clutch to do what synchros are supposed to do, i.e. to save them since they wear out quick
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