Originally Posted by captainaudio
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.
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.