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Toe Heel Shifting?
- Thread starter GopherNSX
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Below is one of many past threads you can find by searching the forum. Keep in mind that as with any forum, everything you read should be examined and researched rather than accepted as fact if it is important.
http://www.nsxprime.com/ubb/Forum1/HTML/002327.html
http://www.nsxprime.com/ubb/Forum1/HTML/002327.html
Heel-and-toe downshifting is a method by which you brake, clutch, blip the throttle to bring up the engine revs up to match the engine rpm with the gearbox for the downshift, downshift to the next gear, release the clutch, and transition back to the throttle. This is all done with the right foot on the brake and using the heel (or sometimes sidestepping the right foot) to blip the throttle simultaneously. You can see it in some split-screen in car footage.
A real pro can do this with a Big Gulp in his lap while he shaves.
A real pro can do this with a Big Gulp in his lap while he shaves.
Here's my own example...sometimes it's easier to see. It was difficult for me to think about and learn it, until I saw it actually done. Keep in mind my car isn't as suited as an NSX is for this as my footwell is shapped funky and the pedals are placed weird....but you can still see the heel&toe aspect in this video.
http://www.nextestdrive.net/internalimages/videofiles/AX4_sm.mov
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Got dat ol' vee six cilnder inder?
http://www.nextestdrive.net
http://www.nextestdrive.net/internalimages/videofiles/AX4_sm.mov
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Got dat ol' vee six cilnder inder?
http://www.nextestdrive.net
The video over in this thread shows some good footwork:
http://www.nsxprime.com/ubb/Forum1/HTML/003921.html
http://www.nsxprime.com/ubb/Forum1/HTML/003921.html
The description by ChopsJazz may not have been entirely clear to a novice, so I'll try to fill in a bit now that I have a moment.
The "double" part of the term stems from the fact that the clutch pedal is depressed two separate times. The first time you shift into neutral and release the clutch. You then blip the throttle to bring the engine andtransmission internals up to the speed they will be turning in the lower gear. Next you depress the clutch pedal again, and shift from neutral into the lower gear. If you matched revs properly this would be smooth even if you had no synchros.
In real-time it all happens very fast. The first actuation of the pedal is typically little more than a flick of the foot as you pop into neutral. The second is nearly as quick once your proficient at it, but timing is very important.
However, you will find many knowledgeable people who insist that all this is a thing of the past and no longer necessary due to advanced synchro design. (But there are still plenty of people destroying synchros out there) They will also remind you that the then engine is for acceleration and the brakes are for stopping. (in other words, don't downshift to use engine braking as part of your slowing strategy.) Personally, I spent many years in old cars that I bought with wasted synhros. I became proficient at the DC out of necessity, but now it's a very pleasurable part of the whole driving experience.
But turning back to the nay sayers, they will tell you to skip the first part and wait until you are about to get off the brakes and back on the throttle. At that point, press in the clutch, do the rev-matching throttle blip (with the clutch still in), then execute the shift and let the clutch out. Mind you, in this scenario the rev-matching does nothing to bring the transmission internals up to speed because the transmission is not connected to the engine, but it does keep from straining the drive train and upsetting the car when you let the clutch out.
So, that’s the longer version. If you want to learn it, borrow an old Toyota.
The "double" part of the term stems from the fact that the clutch pedal is depressed two separate times. The first time you shift into neutral and release the clutch. You then blip the throttle to bring the engine andtransmission internals up to the speed they will be turning in the lower gear. Next you depress the clutch pedal again, and shift from neutral into the lower gear. If you matched revs properly this would be smooth even if you had no synchros.
In real-time it all happens very fast. The first actuation of the pedal is typically little more than a flick of the foot as you pop into neutral. The second is nearly as quick once your proficient at it, but timing is very important.
However, you will find many knowledgeable people who insist that all this is a thing of the past and no longer necessary due to advanced synchro design. (But there are still plenty of people destroying synchros out there) They will also remind you that the then engine is for acceleration and the brakes are for stopping. (in other words, don't downshift to use engine braking as part of your slowing strategy.) Personally, I spent many years in old cars that I bought with wasted synhros. I became proficient at the DC out of necessity, but now it's a very pleasurable part of the whole driving experience.
But turning back to the nay sayers, they will tell you to skip the first part and wait until you are about to get off the brakes and back on the throttle. At that point, press in the clutch, do the rev-matching throttle blip (with the clutch still in), then execute the shift and let the clutch out. Mind you, in this scenario the rev-matching does nothing to bring the transmission internals up to speed because the transmission is not connected to the engine, but it does keep from straining the drive train and upsetting the car when you let the clutch out.
So, that’s the longer version. If you want to learn it, borrow an old Toyota.
The main advantage of down shifting is not only for fast turns or hills but in slippery conditions such as heavy rain or iced road, down shifting in those conditions can significantly reduce lose of tracks, hence down shifting in slippery condition is better then braking since braking is what makes the car loose grip...
Heel-and-toe: The process of blipping the throttle in order to syncronize gears while downshifting, and at the same time continuing to have consistent pressure on the brake pedal. It involves using the left side of the right foot for braking while rotating the foot around the ankle and tapping the throttle with the right side if the foot. [from Going Faster, Mastering the Art of Race Driving. The text book of the Skip Barber Racing School.]
The "tapping" with the right foot (mentioned above) is the throttle blip to match engine revs with the drive-train. The purpuse is to avoid shock to the drivetrain and prevent imbalance in the car during downshifting. Any of us who has ever accidentally dropped the transmission into a lower gear and dumped the clutch has felt the car lurch forward, throwing all the weight onto the front tires. If this weight transfer happens mid-corner a spin is certain. Since all your braking is to be done in a straight line ("the brakes slow the car down. You downshift to get the car in the proper gear to exit the corner" pg 94.), and you want to be in a lower gear to exit a corner , the gear change should happen simulateously with the braking.
I'm sorry it's such a long description, but it's worthy of the space. It's a very tricky skill to master, but a very important one as well.
For more info buy the book, it is all covered in chapter 6. Or better yet, go to school! It'll be the best investment you make to go faster.
[This message has been edited by ChopsJazz (edited 05 March 2002).]
The "tapping" with the right foot (mentioned above) is the throttle blip to match engine revs with the drive-train. The purpuse is to avoid shock to the drivetrain and prevent imbalance in the car during downshifting. Any of us who has ever accidentally dropped the transmission into a lower gear and dumped the clutch has felt the car lurch forward, throwing all the weight onto the front tires. If this weight transfer happens mid-corner a spin is certain. Since all your braking is to be done in a straight line ("the brakes slow the car down. You downshift to get the car in the proper gear to exit the corner" pg 94.), and you want to be in a lower gear to exit a corner , the gear change should happen simulateously with the braking.
I'm sorry it's such a long description, but it's worthy of the space. It's a very tricky skill to master, but a very important one as well.
For more info buy the book, it is all covered in chapter 6. Or better yet, go to school! It'll be the best investment you make to go faster.
[This message has been edited by ChopsJazz (edited 05 March 2002).]
Hmmm... My second post was a classic case of not re-reading the original question!! I remembered it as a question about double clutching when in fact it was only about toe/heel shifting, which although a part of DC, does not necessarily include DC. Sorry, but now you know ... the rest of the story.
The latter. Although I downshift sooner than some would recommend, it is only when also on the brakes. I'm not really looking for the engine to significantly add to the deceleration, but I like o get the downshift out of the way so I have more time to settle the car before the turn-in point. (my personal weakness if done differently)
I would disagree with that entirely. (no offense) You have much more control over the brakes than you do "engine braking", and you get to use all four tires. The quickest way to get backwards is what you suggest. In terms of traction, think of it as similar to 2-wheel drive vs. 4-wheel drive when accelerating on a slippery surface.
At NSXPO ’99 (Laguna Seca) Steve Dinan gave an excellent talk about how to drive a street car on a racetrack. One thing he mentioned was that in order to help save the brakes, it was advisable to do a little controlled engine braking; he said about 20% (whatever that means <g>). Obviously, this requires a smooth heel-toe technique—but that’s what good driving is all about—being smooth. This was a mindset change for me because I had always thought of heel-toe downshifting as a smooth means for setting the car up for the proper gear at turn in—not about helping the car slow down too—but I guess it does both if done properly.
At braking points, I find excellent results by smoothly heel-toe downshifting sequentially through the gears and I usually try to hit the downshift around 5-6k and ride it down until the next lower gear if selected would be in the same 5-6k range—this process is subconscious and can be mastered by anyone with enough practice. Last year’s NSXPO at Road America was such a wonderful opportunity to practice heel-toe shifting down through the gears that I think everyone had a chance to improve their technique, I know I did.
Heel-toe not done smoothly (or not at all) will “chirp” the rear wheels during downshift and cause all kinds of balance problems with the car and wear and tear on the transmission, tires, driver, instructor and lap times. It is my opinion that once a driver learns how to drive the racing line then the next step is to start working on smooth heel-toe downshifting before they even think about increasing their speeds and trying to pass their buddies. Nothing bothers me more then watching an otherwise good driver chirp their tires around the racetrack—and nothing makes me more seasick when sitting in the passenger’s seat.
DanO
At braking points, I find excellent results by smoothly heel-toe downshifting sequentially through the gears and I usually try to hit the downshift around 5-6k and ride it down until the next lower gear if selected would be in the same 5-6k range—this process is subconscious and can be mastered by anyone with enough practice. Last year’s NSXPO at Road America was such a wonderful opportunity to practice heel-toe shifting down through the gears that I think everyone had a chance to improve their technique, I know I did.
Heel-toe not done smoothly (or not at all) will “chirp” the rear wheels during downshift and cause all kinds of balance problems with the car and wear and tear on the transmission, tires, driver, instructor and lap times. It is my opinion that once a driver learns how to drive the racing line then the next step is to start working on smooth heel-toe downshifting before they even think about increasing their speeds and trying to pass their buddies. Nothing bothers me more then watching an otherwise good driver chirp their tires around the racetrack—and nothing makes me more seasick when sitting in the passenger’s seat.
DanO
These are all great posts, thanks for all the input. Here's another simple question: I don't do any track driving, although would love to get invovled. So, if I'm slowing from 60 to 0 at a traffic light let's say, should I be downshifting at all or do I use just the brakes?
Zuerst, with all respect intended, an engine brake in any condition cannot be as controllable as a properly biased 4-wheel brake. There are several reasons for this and I’ll touch on a few:
1) Engine braking reduces the effectiveness or renders the anit-lock braking system useless. That is, the anti-lock braking system can’t free up a rear tire that has lost traction due to engine braking. And as you say “locking of the wheel is what makes the car lose grip.” So, I think it is wise to let the anti-lock system work to keep the tires from losing grip.
2) When any deceleration force is applied to the tires, weight shifts from the rear (assuming your traveling forward <g>) to the front. As this deceleration force is being applied, less weight is available at the rear of the car and therefore there is less grip at the rear and more at the front (grip is related to weight). If you are only applying deceleration force to the rear tires, then there is MUCH less stopping potential available than if the force were being applied to the fronts. Ever noticed how fast the rear tires lock up when only using the parking brake?
3) If a driver has a choice of which tires will lose grip first (front vs. rear) a smart driver will choose the fronts. With any steering input, losing grip on the rear tires first will cause a spinning condition that few drivers, if any will be able to recover. Any of us with manual brake biasing on our cars know this fact intimately
I’m not trying to be mean or condescending; I’m just trying to express my opinion which differs quite a bit from yours.
DanO
Just use the brakes. Downshifting to slow the car down without using heel-toe rev-matching just wears the clutch, transmission and engine. I’d rather replace brake pads than a clutch. On the street, it’s difficult to do any hard 5-4-3-2 heel-toe downshifting (without smashing laws and/or cars) but there are lots of opportunities to “blip”, that is throttle match a downshift, like when setting up a pass, or to do a 3-2 heel-toe before a corner you know well. There is no advantage to downshifting for stop signs, except maybe a little heel-toe blip to engage neutral-1 smoothly for a rolling stop.
My opinion, others will be different,
DanO
Of course you'll have more control over the brakes, it's right there for you to step on, but the fact is that the locking of the wheels is what makes the car loose grip...[/QUOTE]
Losing grip is an interesting concept. Remeber that a tire, each tire, has only 100% grip available at any given time. If a tire is simply rolling forward grip isn't much of an issue. If it is trying to turn, then its grip is divided, in some ratio, between turning and rolling, let's say 50/50. If you ask that tire to brake as well, then the forces must be balanced in such a way as to never exceed 100%, maybe 30/30/40.
So, simply turning the wheel a little more, or braking a little harder could cause the tires to lose grip. The brakes can be applied quite aggressively without causing any loss of grip as long as it is done in a straight line (trail braking is a "whole 'nother" issue).
Losing grip is an interesting concept. Remeber that a tire, each tire, has only 100% grip available at any given time. If a tire is simply rolling forward grip isn't much of an issue. If it is trying to turn, then its grip is divided, in some ratio, between turning and rolling, let's say 50/50. If you ask that tire to brake as well, then the forces must be balanced in such a way as to never exceed 100%, maybe 30/30/40.
So, simply turning the wheel a little more, or braking a little harder could cause the tires to lose grip. The brakes can be applied quite aggressively without causing any loss of grip as long as it is done in a straight line (trail braking is a "whole 'nother" issue).
I'm well aware of how ABS works, it is simply an alternation of locking and releaseing the brakes. ABS is designed to MINIMIZE lose of traction, but the short period where the wheel it locked is sometimes enough for the car to skid, where as if you down shift the wheel is still rolling just at a slower rate, hence no periond of dead lock and less chance of losing traction and skid...
Depends what do you mean by downshifting. In general braking using engine (downshifting) is bad. Bad for the transmission, clutch and engine.
Borrowing DanO's post.
If it chirp, that means the wheel lock momentarily. Until the tire friction to the asphalt force the engine to turn at that rate of speed.
And we all know what disaster can happen when you lock your rear tires up.
However, the best way to do is like Steve Dinan said (DanO posted) that it is good to do a little controlled engine braking. Make sure you slow the car down using the brakes and while braking, rev match and down shift, got to pay attention that the rpm is low enough. This on a street car will use engine braking to help slow the car down.
The NSX has about 60% of it weight in the back. And because of the design, weight distribution, and lower center of gravity than most cars, the weight transfer under braking is not as much as front engine cars. Thus the brake balance between the front and rear is very important. That's also why most rear/mid engine cars have the same or close to the same diameter rear rotors.
Borrowing DanO's post.
If it chirp, that means the wheel lock momentarily. Until the tire friction to the asphalt force the engine to turn at that rate of speed.
And we all know what disaster can happen when you lock your rear tires up.
However, the best way to do is like Steve Dinan said (DanO posted) that it is good to do a little controlled engine braking. Make sure you slow the car down using the brakes and while braking, rev match and down shift, got to pay attention that the rpm is low enough. This on a street car will use engine braking to help slow the car down.
The NSX has about 60% of it weight in the back. And because of the design, weight distribution, and lower center of gravity than most cars, the weight transfer under braking is not as much as front engine cars. Thus the brake balance between the front and rear is very important. That's also why most rear/mid engine cars have the same or close to the same diameter rear rotors.
Please understand that I'm not taking shots at you, but when a forum like this is read by people of all knowledge and skill levels, issues related to safety must be debated vigorously by those who feel that the advice given is in error and potentially dangerous.
In this case, the part that scares me in the notion that engine braking via a downshift is safer than brake-braking under wet and slippery conditions. There are times when lifting off the throttle gently and letting the engine slow you a bit before applying the brakes is a good idea. It settle the car and transfers a bit more weight to the front gently. However, if you are going too fast for the current gear because the road is slick, then a downshift and engine braking is not the solution. If you are traveling uphill, then the risk is mild. On level ground it is not a very good idea, and when heading down a hill it is positively a bad idea. (Keep in mind where talking rear-wheel drive here, not to mention mid-engine) There is a very good reason why, even on mid/rear engine cars, the front brakes do the majority of the work. Safety. As others have accurately stated, as you decelerate, weight (and therefore traction) shifts from the rear to the front. Also, you seem to assume more difference in terms of lost traction than really exists between normal breaking and engine braking. For a given effective amount of deceleration, they are the same, but in engine braking you are using only two of four tires, at the wrong end of the car, and with little ability to modulate particularly on a downshift.
I'm sorry, but this is just plain bad advice without far more details of when a degree of engine braking before or in combination with regular braking is appropriate. I think I understand where you’re coming from and I too have been in tenuous situations where I tried to strike a balance between the two to get my car slowed down, but the idea of a downshift at those time is spooky.
In this case, the part that scares me in the notion that engine braking via a downshift is safer than brake-braking under wet and slippery conditions. There are times when lifting off the throttle gently and letting the engine slow you a bit before applying the brakes is a good idea. It settle the car and transfers a bit more weight to the front gently. However, if you are going too fast for the current gear because the road is slick, then a downshift and engine braking is not the solution. If you are traveling uphill, then the risk is mild. On level ground it is not a very good idea, and when heading down a hill it is positively a bad idea. (Keep in mind where talking rear-wheel drive here, not to mention mid-engine) There is a very good reason why, even on mid/rear engine cars, the front brakes do the majority of the work. Safety. As others have accurately stated, as you decelerate, weight (and therefore traction) shifts from the rear to the front. Also, you seem to assume more difference in terms of lost traction than really exists between normal breaking and engine braking. For a given effective amount of deceleration, they are the same, but in engine braking you are using only two of four tires, at the wrong end of the car, and with little ability to modulate particularly on a downshift.
I'm sorry, but this is just plain bad advice without far more details of when a degree of engine braking before or in combination with regular braking is appropriate. I think I understand where you’re coming from and I too have been in tenuous situations where I tried to strike a balance between the two to get my car slowed down, but the idea of a downshift at those time is spooky.
