Driver Manipulation of the "Limit"
01-06-2006, 01:19 AM
#1
Driver Manipulation of the "Limit"
I have to confess that I have found some of the coversations in this forum regarding the "limit" to be a bit puzzling at times, because I get the feeling that different people mean different things when they are talking about the "limit."
I had the chance over the holidays to do a fair bit of reading, including the "speed secrets" series. I found the books to be extremely useful (although they really could stand to be edited), and I "think" that they helped me reach a few "epiphanies" about things I had started to realize at the end of the season, particularly with respect to the "limit."
I think a great definition of the "limit" is the one used in speed secrets: the limit is the point at which you have acheived maximum potential traction for the tires on the car you are driving. Exceeding the limit doesn't mean you have wrecked or spun. Rather, it means that you are on the right hand side of the traction bell curve.
With this understanding, it is clear to me that most of the time I drive slightly under the limit, but I have exceeded the limit several times, and frequently exceed the limit at some points at specific corners. But that really isn't the epiphany. I already knew that the "limit" for a specific car with a specific type of tires at a specific time (i.e., track conditions) would vary according to the line you chose, and that the speed at which you reached the "limit" for the "ideal" line would be higher than for a poor line, but what I didn't really understand is how much control a driver has over the speed at which you reach the "limit" even if he or she is always driving the "ideal" line.
The epiphany really is about the effect of speed changes (i.e., the speed differntial) and driver technique on the "limit," and how a driver's corner entry speed and braking technique can greatly increase the speed at which the driver reaches the "limit" in a corner on the ideal line.
As I currently understand it, the goal of driving is to manage your tire patches effectively, which you acheive by managing weight transfer and balance. Of course, the track forces you to change speeds at certain points, and sometimes drastically so, but changing speed often interferes with what you ideally would want to do with respect to weight management. As such, the more you can minimize your change in speed, the easier it is to acheive a desirable weight transfer, which in turn makes it easier to go faster before you reach the "limit."
During my first year of DEs, and particularly in the 996, I often struggled with understeer, despite having a car with a suspension that was well tuned. I heel/toe well and have smooth inputs (most of the time), and I am usually pretty good at getting back to full throttle aggressively as soon as braking is completed. However, I would not infrequently experience mild understeer between turn in and the apex (or even mild oversteer in the climbing esses at VIR), which made me think that I was at the "limit" of a corner and could not really enter it too much faster because it would cause me to get on the gas more mildly and thus reduce my exit speed (or so I thought).
The solution? Well, I thought it was to ensure that my corner exit speed was slow enough that turn in understeer (or oversteer as the case may be) was easily manageable. Logical conclusion, right? Well, speed secrets helped me understand that I might really be the cause of my own problem, and my solution to the "problem" was probably making it worse. I was taking the usually wise advice of enter slow, exit fast a little too well to heart.
If I instead had been able to overcome the self-presrevation instinct and tried to enter the turns faster rather than slower (of course I am NOT talking about crashing into corners out of control), I could have reduced the speed differential I was forcing the car to undergo, which would have made it easier to achieve balance through the turn and thus increase the speed at which I reached the "limit."
When reading speed secrets and thinking about this issue, I imagined those obstacle races between waiters who are carrying trays with several drinks on them. Once you get going, it is fairly easy to balance the tray with the drinks. It is the starting and stopping that is the hard part. Imagine one of the racers weaving through the obstacles and fighting to balance the tray as he or she slows down to make it around a tight turn and then tries to regain the lost speed. The more the waiter struggles, the more likely he or she is to slow down. Now imagine a second waiter who just flies through the same obstacles. Oddly enough, the second waiter would probably struggle far less with balancing the tray because he or she would not have to slow down or speed up nearly as much, which are the actions that make balancing more difficult.
By braking too early and entering turns too slowly in the 996, I was reducing the speed at which I subsequently reached the "limit." The more I hit the "limit", the slower I thought I needed to enter the turn, which would only compound the problem. Next year, I plan to focus on improving my corner entry by trying not to complete braking too early (which is really only a problem for high speed turns, but those are frequently the most important) or entering corners too slowly.
I think I got a taste of this in the 944, although I didn't realize until now why that was. I had heard so much about how it was hard to regain momentum in a 944, that I was predisposed to avoid using my brakes. As a consequence, I would enter corners faster with a much lighter application of the brakes, so the speed differential wasn't nearly as great as it was in the 996 and thus the "limit" was reached at a higher speed.
Am I making sense? Am I the only one here who seems to learn more from a track session after it is over by reliving it in my mind than I seem to learn while I am driving? i am pretty aware while I am on the track, and I can relive my driving experiences pretty much at will. While I am driving, I am focused on driving, and, due to lack of experience, I don't always have the tools to know what to do in response to what I am experiencing, or even why certain things happen. Afterwards, however, I frequently get those "aha" moments while reliving my track time, and my next session let's me incorprate what I have learned. It is a little embarassing to realize why people who are overly polite look at you funny when you say something before the "aha" moment that is obviously wrong
Obviously I have cabin fever and cannot wait to get back on the track. Hello Laguna Seca next week.
I had the chance over the holidays to do a fair bit of reading, including the "speed secrets" series. I found the books to be extremely useful (although they really could stand to be edited), and I "think" that they helped me reach a few "epiphanies" about things I had started to realize at the end of the season, particularly with respect to the "limit."
I think a great definition of the "limit" is the one used in speed secrets: the limit is the point at which you have acheived maximum potential traction for the tires on the car you are driving. Exceeding the limit doesn't mean you have wrecked or spun. Rather, it means that you are on the right hand side of the traction bell curve.
With this understanding, it is clear to me that most of the time I drive slightly under the limit, but I have exceeded the limit several times, and frequently exceed the limit at some points at specific corners. But that really isn't the epiphany. I already knew that the "limit" for a specific car with a specific type of tires at a specific time (i.e., track conditions) would vary according to the line you chose, and that the speed at which you reached the "limit" for the "ideal" line would be higher than for a poor line, but what I didn't really understand is how much control a driver has over the speed at which you reach the "limit" even if he or she is always driving the "ideal" line.
The epiphany really is about the effect of speed changes (i.e., the speed differntial) and driver technique on the "limit," and how a driver's corner entry speed and braking technique can greatly increase the speed at which the driver reaches the "limit" in a corner on the ideal line.
As I currently understand it, the goal of driving is to manage your tire patches effectively, which you acheive by managing weight transfer and balance. Of course, the track forces you to change speeds at certain points, and sometimes drastically so, but changing speed often interferes with what you ideally would want to do with respect to weight management. As such, the more you can minimize your change in speed, the easier it is to acheive a desirable weight transfer, which in turn makes it easier to go faster before you reach the "limit."
During my first year of DEs, and particularly in the 996, I often struggled with understeer, despite having a car with a suspension that was well tuned. I heel/toe well and have smooth inputs (most of the time), and I am usually pretty good at getting back to full throttle aggressively as soon as braking is completed. However, I would not infrequently experience mild understeer between turn in and the apex (or even mild oversteer in the climbing esses at VIR), which made me think that I was at the "limit" of a corner and could not really enter it too much faster because it would cause me to get on the gas more mildly and thus reduce my exit speed (or so I thought).
The solution? Well, I thought it was to ensure that my corner exit speed was slow enough that turn in understeer (or oversteer as the case may be) was easily manageable. Logical conclusion, right? Well, speed secrets helped me understand that I might really be the cause of my own problem, and my solution to the "problem" was probably making it worse. I was taking the usually wise advice of enter slow, exit fast a little too well to heart.
If I instead had been able to overcome the self-presrevation instinct and tried to enter the turns faster rather than slower (of course I am NOT talking about crashing into corners out of control), I could have reduced the speed differential I was forcing the car to undergo, which would have made it easier to achieve balance through the turn and thus increase the speed at which I reached the "limit."
When reading speed secrets and thinking about this issue, I imagined those obstacle races between waiters who are carrying trays with several drinks on them. Once you get going, it is fairly easy to balance the tray with the drinks. It is the starting and stopping that is the hard part. Imagine one of the racers weaving through the obstacles and fighting to balance the tray as he or she slows down to make it around a tight turn and then tries to regain the lost speed. The more the waiter struggles, the more likely he or she is to slow down. Now imagine a second waiter who just flies through the same obstacles. Oddly enough, the second waiter would probably struggle far less with balancing the tray because he or she would not have to slow down or speed up nearly as much, which are the actions that make balancing more difficult.
By braking too early and entering turns too slowly in the 996, I was reducing the speed at which I subsequently reached the "limit." The more I hit the "limit", the slower I thought I needed to enter the turn, which would only compound the problem. Next year, I plan to focus on improving my corner entry by trying not to complete braking too early (which is really only a problem for high speed turns, but those are frequently the most important) or entering corners too slowly.
I think I got a taste of this in the 944, although I didn't realize until now why that was. I had heard so much about how it was hard to regain momentum in a 944, that I was predisposed to avoid using my brakes. As a consequence, I would enter corners faster with a much lighter application of the brakes, so the speed differential wasn't nearly as great as it was in the 996 and thus the "limit" was reached at a higher speed.
Am I making sense? Am I the only one here who seems to learn more from a track session after it is over by reliving it in my mind than I seem to learn while I am driving? i am pretty aware while I am on the track, and I can relive my driving experiences pretty much at will. While I am driving, I am focused on driving, and, due to lack of experience, I don't always have the tools to know what to do in response to what I am experiencing, or even why certain things happen. Afterwards, however, I frequently get those "aha" moments while reliving my track time, and my next session let's me incorprate what I have learned. It is a little embarassing to realize why people who are overly polite look at you funny when you say something before the "aha" moment that is obviously wrong
Obviously I have cabin fever and cannot wait to get back on the track. Hello Laguna Seca next week.
Last edited by TD in DC; 01-06-2006 at 09:28 AM.
01-06-2006, 10:08 AM
#2
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Good topic Todd. Isn't this exactly what we are striving for, maximizing the grip of the tires to minimize the time spent in the turns? Makes it sound simple, doesn't it? It is the techniques required to do so that make this such a facinating, challenging and addictive hobby. The item that I am always playing with is earlier apexing with higher transition speeds, and a more gradual workup of acceleration verses somewhat later apexing with a little slower transition speeds but harder, more immediate acceleration through the turn. I seem to feel that it is car dependent, i.e. how much balance your car has off-throttle vs the need to accelerate hard to keep the back end planted. The turn itself will also dictate which way it wants to be driven. I will be very interested in following this thread.
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Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
01-06-2006, 10:42 AM
#3
Nordschleife Master
Originally Posted by Larry Herman
The item that I am always playing with is earlier apexing with higher transition speeds, and a more gradual workup of acceleration verses somewhat later apexing with a little slower transition speeds but harder, more immediate acceleration through the turn. I seem to feel that it is car dependent, i.e. how much balance your car has off-throttle vs the need to accelerate hard to keep the back end planted. The turn itself will also dictate which way it wants to be driven.
Originally Posted by TD in DC
I have to confess that I have found some of the coversations in this forum regarding the "limit" to be a bit puzzling at times, because I get the feeling that different people mean different things when they are talking about the "limit."
01-06-2006, 11:32 AM
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Todd, I think that for the 996 I tend to enter turns faster than I did in the 944 so that I can trailbrake more to keep the nose planted. I also turn in earlier to allow that. Once I get on the throttle, the front end unweights and starts pushing so I usually use no to neutral throttle until the apex.
01-06-2006, 12:21 PM
#5
That makes sense. I think the interesting thing about the track is that the solutions to common issues that all drivers face are not always immediately obvious, at least not to me.
It is perfectly normal for new to intermediate drivers to think "wow, I just reached the limit in that corner despite driving on a good line and being smooth, I guess I can't go any faster . . . damn tires." It was a relevation to me to realize that the answer may actually be to increase entry speed and adjust corner entry technique accordingly.
The whole waiter race analogy also helped me in thinking about, and visualizing, other weight management issues. Rear-engined cars like the 996 are more like carrying a tray with the heavy drinks all spread around the edges of the tray, which means your movements need to be even more controlled than in mid-engined cars like the Boxster S, which is like carrying a tray with the heavy drinks stacked as closely as possible to the center of the tray.
I also think it will be useful in terms of being more aware of weight management and balance to visualize a bunch of glasses placed on the roof or hood of my car and fasted with some sort of velcro that lets go if you get too crazy. The effort of trying to keep the imaginary glasses balanced through smoothness in not only driver inputs, but also weight management and balance, might help improve my driving.
I mean, you can do a lousy job of overall weight management and balance despite being silky smooth in your individual inputs (e.g., squeezing on and releasing brakes and throttle smoothly, making nice smooth shifts, and nice smooth steering inputs with quiet hands). I would imagine that you could become so focused on the smoothness of your inputs that you are not as focused as you should be on the overall weight management issues. In the end, your goal is to acheive both, or at least I would think so.
It is perfectly normal for new to intermediate drivers to think "wow, I just reached the limit in that corner despite driving on a good line and being smooth, I guess I can't go any faster . . . damn tires." It was a relevation to me to realize that the answer may actually be to increase entry speed and adjust corner entry technique accordingly.
The whole waiter race analogy also helped me in thinking about, and visualizing, other weight management issues. Rear-engined cars like the 996 are more like carrying a tray with the heavy drinks all spread around the edges of the tray, which means your movements need to be even more controlled than in mid-engined cars like the Boxster S, which is like carrying a tray with the heavy drinks stacked as closely as possible to the center of the tray.
I also think it will be useful in terms of being more aware of weight management and balance to visualize a bunch of glasses placed on the roof or hood of my car and fasted with some sort of velcro that lets go if you get too crazy. The effort of trying to keep the imaginary glasses balanced through smoothness in not only driver inputs, but also weight management and balance, might help improve my driving.
I mean, you can do a lousy job of overall weight management and balance despite being silky smooth in your individual inputs (e.g., squeezing on and releasing brakes and throttle smoothly, making nice smooth shifts, and nice smooth steering inputs with quiet hands). I would imagine that you could become so focused on the smoothness of your inputs that you are not as focused as you should be on the overall weight management issues. In the end, your goal is to acheive both, or at least I would think so.
01-06-2006, 01:50 PM
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i've seen a fun demonstration of good transitions in a video once. it involved having a squash ball hanging from the rearview mirror. the trick was to get the ball swinging (heh heh) but without having it oscillate, meaning, make the turn/transition in such a way as to be able to load up the ball (car) once and definitely, so the force keeps the ball in that direction without having it move back and forth too much.
also, it may be obvious but the driver who can minimize the transition time which in the case of the ball was getting it off the windshield (getting off the brakes) and getting it sideways to the max (turn in) but doing it smoothly, would most likely be quicker
also, it may be obvious but the driver who can minimize the transition time which in the case of the ball was getting it off the windshield (getting off the brakes) and getting it sideways to the max (turn in) but doing it smoothly, would most likely be quicker
01-06-2006, 02:01 PM
#7
Drifting
As I'm in the midst of reading Speed Secrets 2 I'm catching this at the right time. Smoothness is a must. You must practice being smooth before you try hitting the limit. Cause when you are shooting for the limit you shouldn't have to think about what you are doing to get there. I mean, you shouldn't be worrying about the inputs (hands, feet, eyes.....) that should be almost natural at that point. the only thing you should be focusing on at that point is the feel if the car getting to the limit point of adhesion.
Adhesion, of course, depends on the weight distribution of the car (996, Boxster, 928....) Once you get to the point of thinking you should be going faster down the straight, and why you aren't, you can start messing with the turn in point and where to squeeze back on the throttle.
The point I'm at is beginning to squeeze the accelerator just before the apex.
Adhesion, of course, depends on the weight distribution of the car (996, Boxster, 928....) Once you get to the point of thinking you should be going faster down the straight, and why you aren't, you can start messing with the turn in point and where to squeeze back on the throttle.
The point I'm at is beginning to squeeze the accelerator just before the apex.
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01-06-2006, 02:21 PM
#8
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Yes, you are bored, eh?
So are we all. It is always interesting to me that at the end of a season, I am kind of burnt. It takes about 3-4 weeks for that feeling to subside, and for the need for a fix to reappear. It is back!
That is an interesting revelation. The limit is indeed driver specific. Each person has their own standard. For one, the limit is how fast I can go without getting ragged? For another, it is how fast can I go without an off?
Of course technique has a lot to do with it. Slow in Fast out is really only intended to keep novices safe and on-pavement as they commit their subconscious rudiments to mind. After that, the Slow part is placed within parenthesis, meaning as fast as you can without getting ahead of yourself. Approaching advanced status it becomes "At the Limit In, Fast Out."
I think two things that those looking back can realize are that 1) Apexes in many turns become longer as you go faster. 2) You need to tune the car for more oversteer as you improve as a driver, if you want to go faster.
1) That old super late turn in with an apex less than 5' long just does not work when you want to carry a lot of entry speed. I try the student line at times, and feel like I will simply fly off into the weeds. Watkins Glen has many perfect and clear examples; Turns 5, 6, & 9, for example. The apexes in 5, 6, &9 become particularly long as you rim around the inside in a sweet tail out drift. It was quite a revelation to me some years ago that that old saw wouldn't cut no mo!
2) At some point, if you add a little more speed, your front end will not stick enough to turn in with. Most of us probably first think that this is the limit. If we have a moment of reflection - which for me is always during the ride home!
- we might have the tought that we should have tried a different driving approach. Very often, a quick "shake" of the wheel will give you a bit of tail pitch that is helpful. Even a more abrupt turn in is often useful. Either one is not in the begginer handbook, but in the end is does indeed come down to MAKING the car do what you need it to. These both are leading to the 2nd portion of this.
These too will only work for so long, and then you need to look at the car for some help. If you have experimented with various lines and techniques with little improvement, it always comes down to one last detail to help the car turn; oversteer. You do at some point need to get a bit more oversteer to take some of the load off the front tires. This is where the driver is likely to find his limit... his PERSONAL limit. It takes some fortitude to dial in more oversteer. This step will challenge your carefully crafted sense of inner balance and peacefulness, but in the end it is a necessity.
No ownder the 911 has been so effective as a road racer.
So are we all. It is always interesting to me that at the end of a season, I am kind of burnt. It takes about 3-4 weeks for that feeling to subside, and for the need for a fix to reappear. It is back!
That is an interesting revelation. The limit is indeed driver specific. Each person has their own standard. For one, the limit is how fast I can go without getting ragged? For another, it is how fast can I go without an off?
Of course technique has a lot to do with it. Slow in Fast out is really only intended to keep novices safe and on-pavement as they commit their subconscious rudiments to mind. After that, the Slow part is placed within parenthesis, meaning as fast as you can without getting ahead of yourself. Approaching advanced status it becomes "At the Limit In, Fast Out."
I think two things that those looking back can realize are that 1) Apexes in many turns become longer as you go faster. 2) You need to tune the car for more oversteer as you improve as a driver, if you want to go faster.
1) That old super late turn in with an apex less than 5' long just does not work when you want to carry a lot of entry speed. I try the student line at times, and feel like I will simply fly off into the weeds. Watkins Glen has many perfect and clear examples; Turns 5, 6, & 9, for example. The apexes in 5, 6, &9 become particularly long as you rim around the inside in a sweet tail out drift. It was quite a revelation to me some years ago that that old saw wouldn't cut no mo!
2) At some point, if you add a little more speed, your front end will not stick enough to turn in with. Most of us probably first think that this is the limit. If we have a moment of reflection - which for me is always during the ride home!
- we might have the tought that we should have tried a different driving approach. Very often, a quick "shake" of the wheel will give you a bit of tail pitch that is helpful. Even a more abrupt turn in is often useful. Either one is not in the begginer handbook, but in the end is does indeed come down to MAKING the car do what you need it to. These both are leading to the 2nd portion of this.These too will only work for so long, and then you need to look at the car for some help. If you have experimented with various lines and techniques with little improvement, it always comes down to one last detail to help the car turn; oversteer. You do at some point need to get a bit more oversteer to take some of the load off the front tires. This is where the driver is likely to find his limit... his PERSONAL limit. It takes some fortitude to dial in more oversteer. This step will challenge your carefully crafted sense of inner balance and peacefulness, but in the end it is a necessity.
No ownder the 911 has been so effective as a road racer.
01-06-2006, 02:40 PM
#9
Race Director
I believe the limit is determined by car and track. Not the driver. However it is the drivers job to manage the car so that those limits can be achieved. Many prople feel their personal limit is close to the absoulte limit. Well sadly 90% of us are not even close.
Todd is right in that driving is all about managage the contact patch on the tires.
Pick line that keeps the tires evenly loaded and flat. Any change in speed or direction change the contact patchs and tire grip levels. Now of couse there are 50 different ways to balance the tire loading. Novice drivers have 1 or 2 tools in there bags, experts have 20 or 30. Pros have 45. Ayrton Senna had maybe 49?
Seems like Todd just picked up a few more!
Todd is right in that driving is all about managage the contact patch on the tires.
Pick line that keeps the tires evenly loaded and flat. Any change in speed or direction change the contact patchs and tire grip levels. Now of couse there are 50 different ways to balance the tire loading. Novice drivers have 1 or 2 tools in there bags, experts have 20 or 30. Pros have 45. Ayrton Senna had maybe 49?
Seems like Todd just picked up a few more!
01-06-2006, 03:03 PM
#10
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Originally Posted by M758
Now of couse there are 50 different ways to balance the tire loading. Novice drivers have 1 or 2 tools in there bags, experts have 20 or 30. Pros have 45. Ayrton Senna had maybe 49?
01-06-2006, 05:24 PM
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Not to take this totally 
but I heard during one F1 race segment about Ayrton that he actually looked at the color of his tires to see how they were working. Pretty impressive.
but I heard during one F1 race segment about Ayrton that he actually looked at the color of his tires to see how they were working. Pretty impressive.
01-06-2006, 07:07 PM
#13
Originally Posted by Larry Herman
Not to take this totally but I heard during one F1 race segment about Ayrton that he actually looked at the color of his tires to see how they were working. Pretty impressive.
but I heard during one F1 race segment about Ayrton that he actually looked at the color of his tires to see how they were working. Pretty impressive.
On a more serious note, thanks all for the replies. Very interesting.
01-06-2006, 08:59 PM
#14
Race Director
Originally Posted by RedlineMan
You need to tune the car for more oversteer as you improve as a driver, if you want to go faster.
It certainly has changed my way of thinking about oversteer vs understeer and how to drive. Interesting stuff.
01-06-2006, 11:57 PM
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Originally Posted by Geo
I would not make that statement unilaterally. I think it's generally true for most people. HOWEVER, I'm amazed when I read about F1 drivers on the same team setting virtually identical times, yet one perfers a touch of oversteer and the other prefers a touch of understeer. Heck, I was shocked to hear that anyone that wasn't a newbie prefered any understeer.
It certainly has changed my way of thinking about oversteer vs understeer and how to drive. Interesting stuff.
It certainly has changed my way of thinking about oversteer vs understeer and how to drive. Interesting stuff.
I know what you mean. I never quite figured that either. I remember watching somebody's F1 in-car and just marveling at how much understeer there was. He liked it that way, apparently.
Maybe at that limit some guys feel they need it. Other guys go off. I don't know.I know oversteer makes me way more nervous. We should start a thread on Terror while Driving!