IS ABS the definitive way to break at the end of a straight?
01-09-2004, 04:16 PM
#31
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Tim,
what i do not understand is how you expect the car to turn in correctly while ABS is engaged. Yes it will turn but, won't it understeer or more likely, spin.
If I have judged my entry speed properly, I enter the turn at the maximum speed the lateral grip of my tires can give me. I can only get maximum lateral grip if the contact patches are as large as they can be BOTH front and rear. That leaves ZERO percentage of the available 100 percent of grip for braking.
As Mike pointed out, if the car is still braking the weight will be on the front end of the car. The rear tires will have a smaller contact patch and the car will want to spin. Note neither of my cars have psm so no electronics will save me although under the circumstances even PSM will not salvage the situation.
Note too that ABS does not manage the size of the contact patch of the tire. Under full braking with or without ABS the front tires have a much larger contact patch than the rear because of the inevitable weight transfer. That means the front has better grip than the back. Turn under those circumstances and you spin in a 911 unless you are going way slower than the corner permits. Another thing that bothers me is that in my car at least, when ABS comes on the car is not smooth. The brakes are clamping and unclamping the discs and I can feel the vibration in the car not just in the pedal. This doesn't give me the feeling that I have optimum traction at all. Better than a lock up for sure but as I said in an earlier post my instinct for self preservation tells me to slow down way more before I attempt to turn in.
Just be help keep things clear, when I talk about a friction circle, I refer to the polar plot of grip . It shows that given a certain amount of grip call it 100 percent of whatever g force is possible) you can have 100 percent of the grip with a South Vector (braking) or a North (acceleration) or East or West (lateral grip). If you want to brake and turn right at the same time you end up with a 45 degree vector giving you 50 percent braking and 50 percent lateral or turning grip. That's the reason that under normal circumstances braking and turning at the same time in a 911 is sub-optimal. This was clear in the "rocking chair" article posted above.
Mike, in your post, what you called the friction circle I would call "contact patch".
This is an interesting thread. Tim, I suspect you have some special qualifications based on your posts. Do you design ABS system or something?
Now nobody is good enough to hit that exact same speed lap to lap but, decent drivers do get close. We also seem to be talking about "friction circle" in two different ways.
what i do not understand is how you expect the car to turn in correctly while ABS is engaged. Yes it will turn but, won't it understeer or more likely, spin.
If I have judged my entry speed properly, I enter the turn at the maximum speed the lateral grip of my tires can give me. I can only get maximum lateral grip if the contact patches are as large as they can be BOTH front and rear. That leaves ZERO percentage of the available 100 percent of grip for braking.
As Mike pointed out, if the car is still braking the weight will be on the front end of the car. The rear tires will have a smaller contact patch and the car will want to spin. Note neither of my cars have psm so no electronics will save me although under the circumstances even PSM will not salvage the situation.
Note too that ABS does not manage the size of the contact patch of the tire. Under full braking with or without ABS the front tires have a much larger contact patch than the rear because of the inevitable weight transfer. That means the front has better grip than the back. Turn under those circumstances and you spin in a 911 unless you are going way slower than the corner permits. Another thing that bothers me is that in my car at least, when ABS comes on the car is not smooth. The brakes are clamping and unclamping the discs and I can feel the vibration in the car not just in the pedal. This doesn't give me the feeling that I have optimum traction at all. Better than a lock up for sure but as I said in an earlier post my instinct for self preservation tells me to slow down way more before I attempt to turn in.
Just be help keep things clear, when I talk about a friction circle, I refer to the polar plot of grip . It shows that given a certain amount of grip call it 100 percent of whatever g force is possible) you can have 100 percent of the grip with a South Vector (braking) or a North (acceleration) or East or West (lateral grip). If you want to brake and turn right at the same time you end up with a 45 degree vector giving you 50 percent braking and 50 percent lateral or turning grip. That's the reason that under normal circumstances braking and turning at the same time in a 911 is sub-optimal. This was clear in the "rocking chair" article posted above.
Mike, in your post, what you called the friction circle I would call "contact patch".
This is an interesting thread. Tim, I suspect you have some special qualifications based on your posts. Do you design ABS system or something?
Now nobody is good enough to hit that exact same speed lap to lap but, decent drivers do get close. We also seem to be talking about "friction circle" in two different ways.
01-09-2004, 05:48 PM
#32
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OK, onward we go. Good questions.
1. The car will definitely turn in if you are at the correct corner entry speed. What will happen is the ABS system never should take the tire to momentary lock-up like you get when loudly chirping your tires at the limit with normal threshold braking. The ABS system should allow 10-20% slippage (relative speed difference, not slip angle) nowhere near a momentary lock-up.
So, when the tire is at full ABS mode (ABS threshold braking) and you turn in, the ABS system will still only allow 10-20% slip so as you turn in, the slip is too high and the ABS system drops the braking forces directly in line with the build-up in lateral forces to keep the tire on the friction circle. The car will never spin! You will turn in and the braking forces will drop. Try it (in a parking lot or skid pad), it’s neat.
2. Yes, you are correct, equal weighting (equal contact patches) (no weight transfer) will stop better and corner better than an unequal weighted car. But, we are talking about the transition from threshold braking to turn in, then to full turn. You want to do this while staying on the friction circle all the time.
Let’s ignore transitions for a moment. As you said, if you were to enter the corner when braking at the limit (max g’s at 6 o’clock on the g-g plot) at the proper entry speed for max lateral acceleration (assuming a constant radius turn), you would turn in and immediately jump to the 3:00 (or 9:00) position at max lateral g’s, agreed? A real car can’t do this. OK, in reality, you have to transition between the two (long g’s vs. lat g’s)as you load the tires, suspension etc. and bring the car around. Again, the goal of driving is to maximize g loads on the proper line (thus staying on the friction circle the most and the longest). I can cover that point in more detail if you need to but it is critical. The transition time is where you change from full long g’s to full lat g’s.
In order to do this effectively, you have to smoothly (so as to not upset the car), but as quickly as possible normally, transition from full long to full lat. With no ABS car, the only way to do this is ala Mark Donahue, trail brake. You do this by easing off the throttle as you turn in the car. Long g’s fall as lat g’s build, your car turns in and stays on the friction circle traveling on the widest arc your tires will give you from 6:00 to 3:00. The shape of the turn, your speed, tire grip, and driver skill define how quickly you make the transition.
With an ABS car, you don’t let up on the brakes. With your non abs car, when you let up on the brakes in order to initiate turn in, the rear tires did not need to have less braking but they got it anyway. The rears are off the friction circle and not pulling their fair share, and you are now slower. With a 4-wheel ABS car, this doesn’t need to happen and is faster. As the front tires lose braking force because they are turning in, the rears can stay at full braking. This is precisely what Schumi and the others do when they use left foot braking, they are using variable brake bias through the turn by using the throttle! Now, 4 wheel abs is even better than that because Schumi can only vary front and back, two tires at a time. The abs system can do front and back, left and right as well! If one tire hits some sand, only it will ease up. Even Schumi can’t do that.
If you wait until the car settles after threshold braking before you turn in (no threshold braking), you have lost a lot of time on the friction circle. First, while you were relieving long g’s, second while were waiting for the car to settle, third while you were building lat g’s. That’s slow.
Yes, you are dead on with the bad feelings abs braking gives you. It is an ugly feeling, brutish way to drive. You slam on the brakes way around the turn and then stab the throttle immediately after jumping off the brake. Ugly, yucky, unnerving, but damn fast if your ABS and traction systems can keep up.
Yes we are in complete agreement on the friction circle, a lat g- long g plot.
I am haven’t read the rocking chair article again in detail but I am pretty sure he is wrong. I’ll destroy it when I have a chance to read it closely.
I am arranging an extreme driving clinic in Chicago in the June being run by two of the most qualified racing engineers you or I will ever be able to talk with, PhD level no less with amazing resumes. These are my technical coaches and will be conducting the programs. They are also working with Bosch and others on being able to run the data acquisition system off the ECU/PSM system and on possibly modifying the ABS/PSM system for race conditions.
1. The car will definitely turn in if you are at the correct corner entry speed. What will happen is the ABS system never should take the tire to momentary lock-up like you get when loudly chirping your tires at the limit with normal threshold braking. The ABS system should allow 10-20% slippage (relative speed difference, not slip angle) nowhere near a momentary lock-up.
So, when the tire is at full ABS mode (ABS threshold braking) and you turn in, the ABS system will still only allow 10-20% slip so as you turn in, the slip is too high and the ABS system drops the braking forces directly in line with the build-up in lateral forces to keep the tire on the friction circle. The car will never spin! You will turn in and the braking forces will drop. Try it (in a parking lot or skid pad), it’s neat.
2. Yes, you are correct, equal weighting (equal contact patches) (no weight transfer) will stop better and corner better than an unequal weighted car. But, we are talking about the transition from threshold braking to turn in, then to full turn. You want to do this while staying on the friction circle all the time.
Let’s ignore transitions for a moment. As you said, if you were to enter the corner when braking at the limit (max g’s at 6 o’clock on the g-g plot) at the proper entry speed for max lateral acceleration (assuming a constant radius turn), you would turn in and immediately jump to the 3:00 (or 9:00) position at max lateral g’s, agreed? A real car can’t do this. OK, in reality, you have to transition between the two (long g’s vs. lat g’s)as you load the tires, suspension etc. and bring the car around. Again, the goal of driving is to maximize g loads on the proper line (thus staying on the friction circle the most and the longest). I can cover that point in more detail if you need to but it is critical. The transition time is where you change from full long g’s to full lat g’s.
In order to do this effectively, you have to smoothly (so as to not upset the car), but as quickly as possible normally, transition from full long to full lat. With no ABS car, the only way to do this is ala Mark Donahue, trail brake. You do this by easing off the throttle as you turn in the car. Long g’s fall as lat g’s build, your car turns in and stays on the friction circle traveling on the widest arc your tires will give you from 6:00 to 3:00. The shape of the turn, your speed, tire grip, and driver skill define how quickly you make the transition.
With an ABS car, you don’t let up on the brakes. With your non abs car, when you let up on the brakes in order to initiate turn in, the rear tires did not need to have less braking but they got it anyway. The rears are off the friction circle and not pulling their fair share, and you are now slower. With a 4-wheel ABS car, this doesn’t need to happen and is faster. As the front tires lose braking force because they are turning in, the rears can stay at full braking. This is precisely what Schumi and the others do when they use left foot braking, they are using variable brake bias through the turn by using the throttle! Now, 4 wheel abs is even better than that because Schumi can only vary front and back, two tires at a time. The abs system can do front and back, left and right as well! If one tire hits some sand, only it will ease up. Even Schumi can’t do that.
If you wait until the car settles after threshold braking before you turn in (no threshold braking), you have lost a lot of time on the friction circle. First, while you were relieving long g’s, second while were waiting for the car to settle, third while you were building lat g’s. That’s slow.
Yes, you are dead on with the bad feelings abs braking gives you. It is an ugly feeling, brutish way to drive. You slam on the brakes way around the turn and then stab the throttle immediately after jumping off the brake. Ugly, yucky, unnerving, but damn fast if your ABS and traction systems can keep up.
Yes we are in complete agreement on the friction circle, a lat g- long g plot.
I am haven’t read the rocking chair article again in detail but I am pretty sure he is wrong. I’ll destroy it when I have a chance to read it closely.
I am arranging an extreme driving clinic in Chicago in the June being run by two of the most qualified racing engineers you or I will ever be able to talk with, PhD level no less with amazing resumes. These are my technical coaches and will be conducting the programs. They are also working with Bosch and others on being able to run the data acquisition system off the ECU/PSM system and on possibly modifying the ABS/PSM system for race conditions.
01-09-2004, 06:29 PM
#33
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Tim,
I am still puzzled. Permit me to quote your post immediately above:
"1. The car will definitely turn in if you are at the correct corner entry speed. What will happen is the ABS system never should take the tire to momentary lock-up like you get when loudly chirping your tires at the limit with normal threshold braking. The ABS system should allow 10-20% slippage (relative speed difference, not slip angle) nowhere near a momentary lock-up.
If I am at the correct entry speed, I do not need to brake any more! I have finished braking and am in the process of releasing the brakes to get the contact patches the way they need to be. If I am going faster than the correct entry speed then turning anyway with the brakes applied will reduce the rear contact patch and make my car spin no? The correct entry speed would be the fastest entry speed and in order to be fast my car has to be in balance - without an excess amount of weight on the nose of the car which braking would cause?
So, when the tire is at full ABS mode (ABS threshold braking) and you turn in, the ABS system will still only allow 10-20% slip so as you turn in, the slip is too high and the ABS system drops the braking forces directly in line with the build-up in lateral forces to keep the tire on the friction circle.
Again I am puzzled. If I need to be on the brakes with ABS engaged after I turn in, by definition I am entering at too high a speed else why would I continue to brake?
The car will never spin! You will turn in and the braking forces will drop. Try it (in a parking lot or skid pad), it’s neat.
Tim until I fully comprehend what you are suggesting I won't try this. I'd love to see it demonstrated though, but not in MY car.
I also suggest that you DO read the "rocking Chair" article because a famous racing driver contradicts what you have been saying. That doesn't make him right either but his credentials are pretty good. I'll enjoy reading your comments when you find time to demolish the article.
Best,
I am still puzzled. Permit me to quote your post immediately above:
"1. The car will definitely turn in if you are at the correct corner entry speed. What will happen is the ABS system never should take the tire to momentary lock-up like you get when loudly chirping your tires at the limit with normal threshold braking. The ABS system should allow 10-20% slippage (relative speed difference, not slip angle) nowhere near a momentary lock-up.
If I am at the correct entry speed, I do not need to brake any more! I have finished braking and am in the process of releasing the brakes to get the contact patches the way they need to be. If I am going faster than the correct entry speed then turning anyway with the brakes applied will reduce the rear contact patch and make my car spin no? The correct entry speed would be the fastest entry speed and in order to be fast my car has to be in balance - without an excess amount of weight on the nose of the car which braking would cause?
So, when the tire is at full ABS mode (ABS threshold braking) and you turn in, the ABS system will still only allow 10-20% slip so as you turn in, the slip is too high and the ABS system drops the braking forces directly in line with the build-up in lateral forces to keep the tire on the friction circle.
Again I am puzzled. If I need to be on the brakes with ABS engaged after I turn in, by definition I am entering at too high a speed else why would I continue to brake?
The car will never spin! You will turn in and the braking forces will drop. Try it (in a parking lot or skid pad), it’s neat.
Tim until I fully comprehend what you are suggesting I won't try this. I'd love to see it demonstrated though, but not in MY car.
I also suggest that you DO read the "rocking Chair" article because a famous racing driver contradicts what you have been saying. That doesn't make him right either but his credentials are pretty good. I'll enjoy reading your comments when you find time to demolish the article.
Best,
01-09-2004, 06:45 PM
#34
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Bob:
OK, don't have a lot of time right now, need to go get a pizza. The whole point is that the corner entry speed using trailing braking is faster than no trail and the car continues to slow through the turn-in transition. My corner entry speed is higher than yours, and therefore faster!
OK, don't have a lot of time right now, need to go get a pizza. The whole point is that the corner entry speed using trailing braking is faster than no trail and the car continues to slow through the turn-in transition. My corner entry speed is higher than yours, and therefore faster!
01-09-2004, 10:08 PM
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Originally posted by Steve in FL
I always thought the important thing wasn't how fast you entered the corner, it was how fast you exited it.
I always thought the important thing wasn't how fast you entered the corner, it was how fast you exited it.
Previously, I'd enter turn 1's braking zone doing close to 150, and ride my car's ABS while turning, get back on the gas, and throttle out of it. Very unsmooth and unsettling. But it sure felt fast. Now, I limit myself to 130-135 on the big straight, smoothly brake into the braking zone of turn 1 (sans ABS,) get back on the gas before turn-in, and am almost at full throttle by the apex. Way faster.
I'm going slower on the big straight, but faster elsewhere on the track. My times have dropped considerably. Now, this is in a Corvette which will have different characteristics than a rear-engined car. But I have to imagine the "In slow, out fast" mantra still applies, no?
jas
01-09-2004, 11:10 PM
#37
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Of course corner exit is important, but many races are won by the guy with the bigger cajones because he gets right on the friction circle (FC) faster and earlier than the other guys. It takes guts to throw your car right on the fc especially on high speed sweepers because if you make a miss early, your in trouble, you’re on the fc and there is no margin for error. It is also the fastest
OK, let's walk through it. If you have two cars that agree on the ideal line for a turn, and for this example, let's assume that the maximum lateral g's occurs at the apex (not the normal case, I know) at 70 mph. If both of our cars hit the apex at the same speed and track out the same way, what matters is what happens before that point. My trail braking (tb) approach is faster, (but a good abs driven like I am recommending is faster still).
No tb vs tb car.
This notb car approaches the corner at threshold braking. His braking point has to be earlier than the tb car because he has to allow time (equals distance) for the car to drop from tb long g’s to 0 long g in preparation for turn in. My tb car blows right past him at full throttle, braking later and with no tb to 0 long g change. Cool so far huh?.
Now let's keep going.
The tb car hits his corner entry point at 70 mph, throws the car into the turn, and holds it at that speed until the apex. It took the tb car time to build up the lat g's to get to the max at the apex. You are correct that the notb car can turn in faster (he has more grip, or as you seem to prefer more contact patch available) than my tb car but I am turning in earlier and at a higher speed.
My car is going 75 mph at the tb car turn in point (earlier point probably than the notb car). It then passes the notb car turn in point at 73 mph (3 mph faster), and is still dropping long g’s and building up lat g’s.
We both hit the apex at 70 mph at the lat g limit of our cars, I just did it well before the notb car because I was faster through the entry section. How did I do this, I stayed on the fc for more of the time than the notb car, and I won the race.
OK, let's walk through it. If you have two cars that agree on the ideal line for a turn, and for this example, let's assume that the maximum lateral g's occurs at the apex (not the normal case, I know) at 70 mph. If both of our cars hit the apex at the same speed and track out the same way, what matters is what happens before that point. My trail braking (tb) approach is faster, (but a good abs driven like I am recommending is faster still).
No tb vs tb car.
This notb car approaches the corner at threshold braking. His braking point has to be earlier than the tb car because he has to allow time (equals distance) for the car to drop from tb long g’s to 0 long g in preparation for turn in. My tb car blows right past him at full throttle, braking later and with no tb to 0 long g change. Cool so far huh?.
Now let's keep going.
The tb car hits his corner entry point at 70 mph, throws the car into the turn, and holds it at that speed until the apex. It took the tb car time to build up the lat g's to get to the max at the apex. You are correct that the notb car can turn in faster (he has more grip, or as you seem to prefer more contact patch available) than my tb car but I am turning in earlier and at a higher speed.
My car is going 75 mph at the tb car turn in point (earlier point probably than the notb car). It then passes the notb car turn in point at 73 mph (3 mph faster), and is still dropping long g’s and building up lat g’s.
We both hit the apex at 70 mph at the lat g limit of our cars, I just did it well before the notb car because I was faster through the entry section. How did I do this, I stayed on the fc for more of the time than the notb car, and I won the race.
01-09-2004, 11:15 PM
#38
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Steve and Jasonvp. You guys need a data acquisition system (das) on your car. Until you do this, you don't know for a fact what you are doing or why, you only have guess and opinion. The DAS shows you if you are on the fc and if you are really faster or not. It can tell you if you are braking and steering at the limit. It will tell you if your car is set up right or weather you are understeering at corner entry and oversteering on the exits. And much, much more.
If you guys really want to, I can pull some examples off the DAS I installed on my Lambo and show you just how invaluable it is.
If you guys really want to, I can pull some examples off the DAS I installed on my Lambo and show you just how invaluable it is.
01-09-2004, 11:29 PM
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Originally posted by ColorChange
You guys need a data acquisition system (das) on your car. Until you do this, you don't know for a fact what you are doing or why, you only have guess and opinion.
You guys need a data acquisition system (das) on your car. Until you do this, you don't know for a fact what you are doing or why, you only have guess and opinion.
"Slow is smooth, smooth is fast, in order to go fast you HAVE to go slow."
My personal on-track experience over the last 7 years as brought me to this conclusion. It may work better for you to TB into a corner, but it doesn't work well for me. I might be going into the corner faster, but I pay for it later with an unsmooth exit..
I agree with Bob's earlier comment re: your condescending attitude. You've got a lot of good ideas, but you sound awfully arrogant when you present them. That'll tend to make people think twice about listening to you objectively.
jas
01-10-2004, 12:44 AM
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I can see ColorChagne's point from a pure technical point of view.
i.e. No car can utilize max traction on all 4 tires at the same time during the entire cornering process with just human controlling the brake. We can't adjust break force on each wheel individually. We also can't control the power distributed to each wheel separately. BUT, the machine CAN!
I can imagine a correct ABS + PSM + traction control system specifically designed for the tracks would out perform any human being driving the traditional way. You can even throw in variable suspension that electronically adjusts the height and stiffness of individual shock thousands of times a second. Us human would not be able to do that and thus will be slower.
In practice, only a side by side test would tell which one is faster.
i.e. No car can utilize max traction on all 4 tires at the same time during the entire cornering process with just human controlling the brake. We can't adjust break force on each wheel individually. We also can't control the power distributed to each wheel separately. BUT, the machine CAN!
I can imagine a correct ABS + PSM + traction control system specifically designed for the tracks would out perform any human being driving the traditional way. You can even throw in variable suspension that electronically adjusts the height and stiffness of individual shock thousands of times a second. Us human would not be able to do that and thus will be slower.
In practice, only a side by side test would tell which one is faster.
01-10-2004, 01:25 AM
#41
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Jason: Again, I apologize for any condescension. My off hand comments are intended to make the fairly technical discussion more interesting. If it offends, I will try to stop.
You are dead wrong (this isn't condescension, it is direct communication and statement of indisputable fact) that if you do not have data acquisition, and the only data you have is for lap times, you only know your overal lap performance. You know (I'm an engineer, if you don't have the data, you don't know and can prove nothing) nothing about individual corners just like we are discussing. You have no idea of your level of variability within the lap ... I could go on forever.
The only reason tb does not work for you is that you aren't doing it right. DAS would show you that. It is a great thing to have a pro driver take your car around the same track you are driving and compare your driving to his. It is highly educational to say the least.
Ypshan: You are absolutely correct. Now, since I have not had my turbo out on the track (long story) and my new one is not here yet, and has no DAS, I can’t prove what I am saying with these P cars, and I can’t tell you how good or bad the abs and psm systems are. I will have the data and will be able to show the data before the end of the summer. I can also site numerous technical references if someone is interested in more reading. These aren’t my original ideas and I am discovering nothing new on my own.
You are dead wrong (this isn't condescension, it is direct communication and statement of indisputable fact) that if you do not have data acquisition, and the only data you have is for lap times, you only know your overal lap performance. You know (I'm an engineer, if you don't have the data, you don't know and can prove nothing) nothing about individual corners just like we are discussing. You have no idea of your level of variability within the lap ... I could go on forever.
The only reason tb does not work for you is that you aren't doing it right. DAS would show you that. It is a great thing to have a pro driver take your car around the same track you are driving and compare your driving to his. It is highly educational to say the least.
Ypshan: You are absolutely correct. Now, since I have not had my turbo out on the track (long story) and my new one is not here yet, and has no DAS, I can’t prove what I am saying with these P cars, and I can’t tell you how good or bad the abs and psm systems are. I will have the data and will be able to show the data before the end of the summer. I can also site numerous technical references if someone is interested in more reading. These aren’t my original ideas and I am discovering nothing new on my own.
01-10-2004, 03:00 AM
#42
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Color,
Your confidence is awesome. I'm guessing you haven't tried to trail brake a rwd C2 into a fast corner at the end of a long straight, but when you do, you might find it hard to successfully complete consistently. Each time the car gets more than 10 degrees sideways, the driver winds up very busy with corrections and almost invariably loses time. Maybe you can do it consistently, but I can't in a high-grip car with a big polar moment. That was my experience in my previous C2. I'm at a loss to know how to predict where to hit the brakes in order to so shorten the braking zone that your still into the abs at the transition point. I know how to modulate the brakes, as the braking distances change from lap to lap. But, figuring out the very last possible braking moment to keep the abs engaged seems like more than my butt can sense.
You and Bob don't disagree when it comes to a car like an early C4. My old one would not turn in unless you were on the anti-lock. But, I believe that had something to do with the design intent of unlocking the front wheel drive only in certain circumstances. That car needed to lose rear wheel grip to rotate.
The current awd tt is a very forgiving car that fundamentally understeers (at least that's how it feels to me). So when Bob referenced the technique of trail braking, I believe he credited it with helping to rotate the car, which allows you to get back on the gas earlier.
I'm not sure you're giving Bob enough credit for his experience in supporting his contentions. I read the Gentillozi article long ago. Remember, he's a multiple Trans-Am champion, so I'd guess he knows what he's talking about. If he couldn't efectively use your technique in a GT3, I'm pretty sure most of us couldn't either. Trying to do it your way, he finished at the back of the pack. So, I'd surmise that there's a little more to it than theory. I'll be curious about your experiences at Gingerman when you get to try out your new car. If you're consistently engaging the abs into the apex of corner 1, I'll help you clean off the grass and sand. AS
Your confidence is awesome. I'm guessing you haven't tried to trail brake a rwd C2 into a fast corner at the end of a long straight, but when you do, you might find it hard to successfully complete consistently. Each time the car gets more than 10 degrees sideways, the driver winds up very busy with corrections and almost invariably loses time. Maybe you can do it consistently, but I can't in a high-grip car with a big polar moment. That was my experience in my previous C2. I'm at a loss to know how to predict where to hit the brakes in order to so shorten the braking zone that your still into the abs at the transition point. I know how to modulate the brakes, as the braking distances change from lap to lap. But, figuring out the very last possible braking moment to keep the abs engaged seems like more than my butt can sense.
You and Bob don't disagree when it comes to a car like an early C4. My old one would not turn in unless you were on the anti-lock. But, I believe that had something to do with the design intent of unlocking the front wheel drive only in certain circumstances. That car needed to lose rear wheel grip to rotate.
The current awd tt is a very forgiving car that fundamentally understeers (at least that's how it feels to me). So when Bob referenced the technique of trail braking, I believe he credited it with helping to rotate the car, which allows you to get back on the gas earlier.
I'm not sure you're giving Bob enough credit for his experience in supporting his contentions. I read the Gentillozi article long ago. Remember, he's a multiple Trans-Am champion, so I'd guess he knows what he's talking about. If he couldn't efectively use your technique in a GT3, I'm pretty sure most of us couldn't either. Trying to do it your way, he finished at the back of the pack. So, I'd surmise that there's a little more to it than theory. I'll be curious about your experiences at Gingerman when you get to try out your new car. If you're consistently engaging the abs into the apex of corner 1, I'll help you clean off the grass and sand. AS
01-10-2004, 09:17 AM
#43
Three Wheelin'
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AS, I don't mean purposely try to sound so confident but I have spent quite a bit of time reading and thinking about this. I am probably not correct on everything I have stated but I am quite confident that overall, I am right.
As regards to driving specific cars or my ability to do it, I have never said how to do it or that I was great ... believe me, I'm not. What I am saying is that a great driver does/would drive this way. I may be in the same boat as you (in the tt) and have great difficulty doing it on the track as you. I'll know next summer.
The biggest problem I have with any racer (not Bob specifically) who does not have data is he only has opinion. This is why there are so many false “truths" out there in racing. Very few people are technical enough to understand what they are doing and why, and further, have the data to back it up.
The reason I am taking time to explain all of this is that unlike most racers, Bob appears to have an open mind and is trying to learn, just like me. I can guarantee you, Bob would have a whole lot to teach me out on the track, ... but I'm learning fast Bob!
When you say Gentilozzi is a trans am champ so must know what he is talking about is flat out wrong. It means he is good at driving fast, he may not know why or be able to explain it, and furthermore, it is in his best interests to lie and try to confuse those who don't understand. Had you thought of that? Again, being a good driver says nothing about being a good engineer or understanding what you are doing., and Mark Donahue would have never told you the truth about what he was doing while he was racing. He wouldn't want to give up his Unfair Advantage. Types like Mark Donahue or are very rare.
As regards to driving specific cars or my ability to do it, I have never said how to do it or that I was great ... believe me, I'm not. What I am saying is that a great driver does/would drive this way. I may be in the same boat as you (in the tt) and have great difficulty doing it on the track as you. I'll know next summer.
The biggest problem I have with any racer (not Bob specifically) who does not have data is he only has opinion. This is why there are so many false “truths" out there in racing. Very few people are technical enough to understand what they are doing and why, and further, have the data to back it up.
The reason I am taking time to explain all of this is that unlike most racers, Bob appears to have an open mind and is trying to learn, just like me. I can guarantee you, Bob would have a whole lot to teach me out on the track, ... but I'm learning fast Bob!
When you say Gentilozzi is a trans am champ so must know what he is talking about is flat out wrong. It means he is good at driving fast, he may not know why or be able to explain it, and furthermore, it is in his best interests to lie and try to confuse those who don't understand. Had you thought of that? Again, being a good driver says nothing about being a good engineer or understanding what you are doing., and Mark Donahue would have never told you the truth about what he was doing while he was racing. He wouldn't want to give up his Unfair Advantage. Types like Mark Donahue or are very rare.
01-10-2004, 02:27 PM
#45
Burning Brakes
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Originally posted by ColorChange
Steve and Jasonvp. You guys need a data acquisition system (das) on your car. Until you do this, you don't know for a fact what you are doing or why, you only have guess and opinion. The DAS shows you if you are on the fc and if you are really faster or not. It can tell you if you are braking and steering at the limit. It will tell you if your car is set up right or weather you are understeering at corner entry and oversteering on the exits. And much, much more.
Steve and Jasonvp. You guys need a data acquisition system (das) on your car. Until you do this, you don't know for a fact what you are doing or why, you only have guess and opinion. The DAS shows you if you are on the fc and if you are really faster or not. It can tell you if you are braking and steering at the limit. It will tell you if your car is set up right or weather you are understeering at corner entry and oversteering on the exits. And much, much more.
You have an interesting theory but as you stated in your original post you haven't tested it yet. Until you can present factual data showing your theory works in the real world allow us some skepticism. My personal experience with the interaction of ABS and PSM the first time I took my Boxster S out at Sebring is it did _not_ make for a fast line through the corners. What it did do is remind me rather vividly that you can't drive a Boxster S like a 911T (the latter is much easier to steer with the throttle). And this is where I think your theory breaks down - different cars will have different lines. Sure there's the theoritical ideal constant radius arc in a turn but it hasn't been my experience that is always used in the real world. There's also the problem is that your theory relies on PSM to save your bacon when turning your car under ABS gets you out of shape. If you don't have PSM what do you do?
