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Discussion Starter #1
I was asked by a board member after driving his car about this, but rather than just PM him the info I think I'll make a whole thread about it.
This thread will be about how to rev match and double clutch downshift, including how to heel and toe. This information is spread out over the board, but with questions being asked recently it might seem applicable to many members.
When downshifting a manual tranny, the RPM's must increase. Anyone knows that when you upshift in a manual, you let off the gas. That is because as the gears go numerically higher, the rpms are lower in the next gear. The inverse is true on downshifts. As you go down gears, the rpms need to increase.
When most of the manual driving population drive stick, a downshift is executed by clutching in, shifting to the lower gear, and then slowly letting the clutch out. This is not the correct way to do this if you want to save some life on your clutch, or at the least begin to downshift smoothly. When you do this you drag the engine rpms back up to the speed they need to be in the lower gear, and by doing so cause clutch slip (although it is minor) and in some cases can destabilize the car.
A better way to downshift is a simple rev match, or if you are inclined a double clutch downshift. A rev match downshift is completed by clutching in, selecting the lower gear, and while you are doing this bliping the throttle to the approximate rpm the car should be in the lower gear you selected. If this doesnt make sense, simply drive at 65 mph in 5th gear. Upshift to 6th, and note the rpm drop from the upshift. To get back into 5th gear, clutch in, select 5th gear, and then blip the rpms to where they were in 5th gear. Let the clutch out, and the downshift should be smooth.
Many people on this board have asked "what rpm should I blip to??" The best answer to that is blip it to where it needs to go. I know that is a bit of a loaded answer, but it depends to gear selection and speed. To learn, pick a downshift. I teach my friends to downshift from one gear to another at a similar speed until they get the rpm difference down right, and are able to execute a smooth downshift from that one speed. Pick one that works for you, and one that fits into your commute or drive for maxiumum practice.
When I blip (and technique will vary) I blip by tapping the throttle quickly till I see the rpm increase I want, and then a little more. When the RPM's start falling back down, and then fall to where they should be in the lower gear, I'll pull the clutch out. I dont hold a throttle input when I pull the clutch out at all.
I recomend working out the foot work in your driveway with the car off. This way you can put your car in a high gear, and then get the muscle memory up to clutching in, shifting, and blipping in one smooth moment. Once you have the muscle memory down perfect, take the car out and try it. Just dont try doing this near corners, as you might make a mistake, and with 394hp on tap you might want to be careful.
Double clutching takes rev matching one step further. The purpose of this is to rev match the internals of the transmission, so when you select the lower gear the synchros have little or no load. When the synchros has little or no load the tranny will select the gear without hesitation. To double clutch you "simply" clutch in, select neutral, clutch out, blip, clutch in, select the lower gear, and then clutch out. It sounds a lot more complicated than it is, so once again I recomend building the muscle memory when the car is off before I try it live. Anyone who has tried to select 1st gear at 30 mph has felt this hesitation in the gearbox, but by duoble clutching the gear will slot in with no pause or crunch.
Finally we come to heel and toeing. This is for someone who has mastered rev matching (double clutching isnt that important, but you need to know how to blip the throttle for a downshift). A correct heel and toe is the rev matching mentioned above while you are depressing the brake pedal. The point of this is being able to charge a corner at a high rate of speed, scrub the speed off with the brakes, and then be able to downshift the car to exit the corner at the highest possible rate of speed in the correct gear.
To heel and toe you must be able to rev match downshift off the brakes. I say this again as heel and toeing builds off rev matching, so if one if sub par both will be. Once you have rev matching down, build the muscle memory of heel and toeing by sitting again with the car off. The left few toes of your right foot should be pushing the brake, and the right side of your foot should be able to be rocked over to the gas to push it hard enough to get the "blip" you need for the downshift. People with smaller feet might need to rock their whole foot, and rotate their foot around the ball of their foot to hit the gas with their heel, but in the case of the E39 this shouldnt be a huge problem (no offense to those with small feet :D ). Since you are on the brakes, the amount you will blip will be less than if you were not heel and toeing, since when you heel and toe you are decelerating. It varies from car to car, but given enough practice you will learn how much to blip.
Hopefully this helps to those board members who dont know how to heel and toe, double clutch and rev match downshift...and those who have been shown (looking at a certain LMB beast in the Bay Area ;) ) and those who want to learn. If I missed anything, feel free to comment, and any questions anyone might have can be addressed in this thread or by PM. I want to make a video of this, but since Greg already has a video out there is little point in me doing so. Hopefully all the E39 owners can learn this and then stand out against SMG! (ok, maybe I am a little too hopeful on that :D )
:cheers:
 

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BmwNut

Nice writeup and good summary. I learned "double" clutching (or more properly double de-clutching) having 2 blips: the blip when the gear selector is in neutral with clutch out and a second blip with clutch in just before you change gears. The first, as you say, is to get the synchros spinning and the second is to match the gears.
On modern cars with synchros most cars can be downshifted with a single blip, (no stop in neutral required) although I have found the double blip seems to work well on my E39. :noSMG:. For track driving I invariably use the single blip (but then I don't drive FF's! :1: )
Regards,
Jerry
 

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Heel toe is a bit of a misnomer (sic?), as Mr Nut implied it is more rolling your foot onto the gas. I find the m5 very easy to do this is as the pedals are spaced nicely. Try pushing the gas and the brake together with one foot while stopped or even with the engine off. I think this is a good way to start to feel where your foot is going to need to be to on both pedals.
 

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BmwNut said:
Just dont try doing this near corners, as you might make a mistake, and with 394hp on tap you might want to be careful.
Nice writeup BmwNut.
But here's a little more clarification for the inexprience.
On the track and street, NEVER NEVER attempt a down shift in a corner.
All braking and down shifting must be completed in a straight line and before entering the corner as to achieve maximum tire grip from braking, settling the chassis for the corner and then be in the right gear for accelarating out of the corner.
 

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I understand the concept of double clutching while downshifting and can do it fairly smoothly, but I have one question. Why would you want to double clutch while upshifting? I have a frend that tells me that is reduces wear on the synchros, but if you shift slow enough, won't the transmition "match rev" itself? Also, wouldn't you have to wait for the RPMs to drop to properly match rev the transmition internals? Thanks
 

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Discussion Starter #9
Double clutch upshifting is useless in a modern gearbox. Upshifting is not something modern synchros have a hard time doing. But in the end for the tranny internals to be rev matched correctly, the clutch should be out, which woudl require a double clutch. Just shift at a normal pace on an upshift and you'll be fine.
canysmc- Totally agree. I just cautioned those who might try this near a corner, and that can have bad results. You are 100% in saying get all of your braking done in a straight line. Unless you trail brake, but that is a different story.
:cheers:
 

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I have 2 questions:
1. When rev matching to downshift, is there any difference in technique or the best revs to be at when you are downshifting to accelerate vs downshifting to use engine braking to slow down or stop?
2. My problem with learning to heel and toe is using a few toes on the brake pedal doesn't give me the confidence to slow quickly enough, especially at the end of a 120mph straight at the track. On the street, not enough braking is needed to get the feel how to do it at the track. Any ideas on how to practice this safely?
 

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canysmc said:
All braking and down shifting must be completed in a straight line and before entering the corner as to achieve maximum tire grip from braking, settling the chassis for the corner and then be in the right gear for accelarating out of the corner.

The e39 M5 REALLY responds well to a bit of trail braking (carrying a little bit of brake pressure as you're turning in). This works well to put a little extra weight on the front wheels to help with turn in. If it's your first time on the track, maybe do all of your braking in a straight line, but ultimately, you will carry more momentum thru the corners with a little trail braking. I find that i can be much smoother and faster if i start my turn in as i'm coming off the brakes.
Mike
 

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canysmc said:
All braking and down shifting must be completed in a straight line and before entering the corner as to achieve maximum tire grip from braking, settling the chassis for the corner and then be in the right gear for accelarating out of the corner.
Like Mr. Nut says... straight line braking and shifting is fine and dandy for most... but developing trail braking as a skill will make you a LOT faster on the track. And for an understeering car like the M5, trailbraking is an essential skill :wroom: The friction circle is your friend, nothing wrong with spreading the available grip around.... 20% braking (to get some weight on the front tires) and 80% cornering = Faaast lap times :byee55amg

A gentle way to learn trail braking... move your braking points up a little bit, and don't brake as hard... practice finesssing the brake pedal... lightly trailing off the brake as you turn in will bring a giant smile to your face as understeer disappears... its a great feeling :hihi:
 

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mottati said:
The e39 M5 REALLY responds well to a bit of trail braking (carrying a little bit of brake pressure as you're turning in). This works well to put a little extra weight on the front wheels to help with turn in. If it's your first time on the track, maybe do all of your braking in a straight line, but ultimately, you will carry more momentum thru the corners with a little trail braking. I find that i can be much smoother and faster if i start my turn in as i'm coming off the brakes.
Mike
LOL you beat me to the punch! :M5thumbs:
 

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CarbonBeast said:
A gentle way to learn trail braking... move your braking points up a little bit, and don't brake as hard... practice finesssing the brake pedal... lightly trailing off the brake as you turn in will bring a giant smile to your face as understeer disappears... its a great feeling :hihi:
Yes, but remember, GET BACK ON THE THROTTLE IMMEDIATELYto balance the car or the rear end will keep coming around!! :D I see too many students take a break (no pun intended!) between the end of the trail braking and getting back on the gas. Makes for an "interesting" lap!! Student, "What's that smell, brakes?"...Instructor, "Uh, I think it is inside the car!" hiha hiha
Regards,
Jerry
 

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Richard in NC said:
I have 2 questions:
1. When rev matching to downshift, is there any difference in technique or the best revs to be at when you are downshifting to accelerate vs downshifting to use engine braking to slow down or stop?
2. My problem with learning to heel and toe is using a few toes on the brake pedal doesn't give me the confidence to slow quickly enough, especially at the end of a 120mph straight at the track. On the street, not enough braking is needed to get the feel how to do it at the track. Any ideas on how to practice this safely?
Richard
I don't use the engine to brake (unless in an emergency, or I miss the blip on my downshift and then I ease the clutch out very carefully so as not to upset the car), that is what the brakes are for. If you rev match correctly on your downshift, you don't even feel it while the car is under braking.

WRT heel and toe, it is a misnomer today. Most people use the ball of their foot for the brake and the right side of their foot for the gas. I have seen variations, do what is comfortable for you. I found the M5 pedals a little too far apart and the brake pedal too low, so I have a little brake pedal cover extension made. Really helps for me. YMMV.
Regards,
Jerry
 

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Discussion Starter #17
As I said, trail braking is a different story but as you guys have said a very important one. My 528 would plow till the cows came home when pushed hard unless I trailbraked. Think of it as a pulley system, as for every amount of steering that goes in, you release the brakes slowly. Setting the suspension before a corner is important when you are looking for lap times and or cornering speed. That's why heel and toeing is important, as the power available in a higher gear might not be enough to get the suspension loaded up where you want it to be.
Richard- There really isnt any magical RPM to be at, rather you want to downshift only when you have lost flexibility in the gear you have. If you cant power out of a corner and need a lower gear, then it is time to downshift. If you can anticipate the gear based upon how much you have slowed down, then grab the lowest gear you can based upon your speed.
In regards to how to practice to get a good feel, find a deserted road. Speed up to 60mph, climb on the brakes and then practice getting it down a gear or so. It wont be the same as scrubbing off speed from 120mph, but the time interval will be quicker, so if you can brake hard and heel and toe from 60 down to 20 mpg you should be fine going from 120mph to 50 or so. Once you get used to it you will be able to heel and toe with any brake application, soft or firm.
CarbonBeast- Hey now, Mr. Nut is my father! hiha
:cheers:

I
 

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BmwNut said:
That's why heel and toeing is important, as the power available in a higher gear might not be enough to get the suspension loaded up where you want it to be.

:cheers:

I
Hadn't heard that reason before. I always understood the lower gear was to get the engine in the proper power band to have as much power as possible to accelerate out of the corner. If you are in too high a gear, the suspension should still set,(suspension doesn't know what gear you are in as you charge into a corner) but when you hit the go pedal, there is no torque and hence no power to get the car through the turn properly. :cheers:
Regards,
Jerry
 

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Discussion Starter #19
I do a fair amount of throttle steering when I drive hard, and in my experiance keeping the engine at a high rpm helps keep the suspension loaded based upon what I dictate with my right foot. It's hard for me to explain. I found in my E39 528 that if I came out of corners as hard as I could (speed wise) I had a slight bit of oversteer, and the throttle allowed me to keep the suspension set, where as when the gear selection was high I couldnt load up the rears the way I wanted to. You are right though, as on corner entry the throttle isnt usually used to set the suspension. Corner exit is a different story.
:cheers:
 
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