How does "throwing away" grip make the car faster?
03-25-2009, 09:03 PM
#1
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Thread Starter
Join Date: Feb 2007
Location: Texas
Posts: 162
How does "throwing away" grip make the car faster?
I have what might be a very simple question, but I just don't get it even after reading a couple of the suspension books and spending way too much time online.
My car has CC plates which, with the increased front camber, should add front grip and make the car faster.
I also have Vogtland lowering springs, which lower the CG and should add total grip due to less weight transfer.
So now I have a certain amount of front and rear grip. The car still understeers.
With sway bars I can decrease rear grip and make the car more neutral. But I don't think that will increase front grip. Is that true?
So my question is, if my car understeers now, how do sway bars make the car faster since they don't increase front grip, they just "throw away" rear grip?
- Wayne
My car has CC plates which, with the increased front camber, should add front grip and make the car faster.
I also have Vogtland lowering springs, which lower the CG and should add total grip due to less weight transfer.
So now I have a certain amount of front and rear grip. The car still understeers.
With sway bars I can decrease rear grip and make the car more neutral. But I don't think that will increase front grip. Is that true?
So my question is, if my car understeers now, how do sway bars make the car faster since they don't increase front grip, they just "throw away" rear grip?
- Wayne
03-26-2009, 12:40 AM
#2
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Join Date: Aug 2007
Location: College Station, TX
Posts: 2,179
Good question. I would assume it has to do with decreasing momentum caused by body roll. It's a bit late for me too give it much thought, because when I re-read the post tomorrow, it won't make sense and I'll feel like an idiot.
03-26-2009, 07:13 AM
#3
Join Date: May 2008
Location: Virginia
Posts: 40
I've got the Vogtland springs on my Bullitt along with camber plates from Maximum Motorsports; I also have some Addco sway bars Sam Strano recommended, as well as Koni adjustable shocks. I have the front sway bar set to the middle hole for moderate stiffness (which is more than the OEM bar). The rear bar is actually not very big, though it might be slightly bigger than OEM. Sam steered me away from a bigger rear bar. In doing so, I'd say he was steering me away from "throwing away rear grip." I need both ends to stick.
The car handles very well. I'm finding that adjusting the shocks can tune a lot of the understeer out of the car. Your post didn't mention what shocks you're running. I'd suggest calling Sam (check out www.stranoparts.com, too) and talking it through with him. He'll get you to more neutral handling for not much $.
The car handles very well. I'm finding that adjusting the shocks can tune a lot of the understeer out of the car. Your post didn't mention what shocks you're running. I'd suggest calling Sam (check out www.stranoparts.com, too) and talking it through with him. He'll get you to more neutral handling for not much $.
03-26-2009, 10:54 AM
#4
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Join Date: Feb 2007
Location: state of confusion
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I also have Vogtland lowering springs, which lower the CG and should add total grip due to less weight transfer.
So now I have a certain amount of front and rear grip. The car still understeers.
So now I have a certain amount of front and rear grip. The car still understeers.
With sway bars I can decrease rear grip and make the car more neutral. But I don't think that will increase front grip. Is that true?
So my question is, if my car understeers now, how do sway bars make the car faster since they don't increase front grip, they just "throw away" rear grip?
So my question is, if my car understeers now, how do sway bars make the car faster since they don't increase front grip, they just "throw away" rear grip?
For a given car there will be a specific total amount of lateral load transfer. If the front tires "saturate" at some point and can develop no more lateral force, while the rear tires still have more grip available, shifting some of the lateral load off the front tires gives them back a little grip at that same point (where they were all done before). As long as you haven't saturated the rear tires, you now have a little more cornering capability.
A smaller effect is that adding any roll stiffness will reduce roll, which generally improves the camber situation for the front tires (and hence their lateral grip). Rear tires on a stick-axle car are not much subject to camber variations, and their grip relative to chassis roll remains essentially constant. Just be aware that keeping things in balance is what you're after, so don't just go crazy after the stiffest parts you can find.
Tex - momentum in roll and overshooting of the final suspension position if you're getting excessive roll velocity (momentum) is more of a shock/strut damping issue. It's part of transient behavior and related to suspension velocities, not the steady-state and/or suspension position stuff that springs and bars react to.
Norm
Last edited by Norm Peterson; 03-26-2009 at 11:23 AM.
03-26-2009, 12:12 PM
#5
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You're going to hate this.... When does it understeer? All the time? Sometimes? On the way in? mid-corner? On the way out? What are you doing with your feet? I ask because I recall a long conversation in which I told you that using the brake and gas at the same time (he's a left footer and the car is an automatic) will confuse things.
Left foot braking cannot change the laws of physics. In fact, more to the point just last weekend I had a student in a C6 Corvette who's LFBing was just completely screwing him. There is nothing wrong with it *done correctly* and in fact in theory it's faster. But most don't do it correctly, and I recall in out conversation that there was something that led me to believe you were using it as a crutch. The man in the C6 told me he'd be doing it for 25 years and felt he was good at it. He wasn't. Every time we'd try and slow down, he'd still have some throttle on and you could just feel the car fight itself. We worked on it for a while, but he could not get off the gas (habit I guess). I made him right foot brake and changed nothing else. We almost spun twice on the first run because we had a lot more front grip but he was turning like he had been before. No other changes. So you need to make 1000% sure you aren't confusing things by dragging the brakes when on the gas, or dragging the gas when on the the brakes.
That said, just chaning tires can and will change the balance of a car. Tire pressures, alignment, bars, etc. etc.
Does taking grip from and end make a car faster? Only if you can't get the car balanced any other way.... My rule of thumb is simple. Maximize grip at both ends (including making sure the driver isn't causing the push if there is one) and tune from there.
I do think the car could use a little better balanced set of bars. I tend to use either a 35/22 combo like the Shelby has, and that I made a prototype set of that Jim in VA now has. I will also use the Hotchkis bars even though the rear is 1" which is normally bigger than I prefer. But I'm ok with it because the front bar from Hotchkis is much larger @ 1.5" so the balance remains good. Also both front and rear bars from the are hollow (most everyone else only runs a hollow front) and both bars are adjustable too. I also have bars from Hellwig, Eibach, H&R and Steeda, as well as the Hotchkis bars. Choices abound, but frankly H&R's rear is too big @ 26mm. Hellwig are both adjustable, but at this time both solid and the rear is 1" (again too big for the front they use IMHO).
Left foot braking cannot change the laws of physics. In fact, more to the point just last weekend I had a student in a C6 Corvette who's LFBing was just completely screwing him. There is nothing wrong with it *done correctly* and in fact in theory it's faster. But most don't do it correctly, and I recall in out conversation that there was something that led me to believe you were using it as a crutch. The man in the C6 told me he'd be doing it for 25 years and felt he was good at it. He wasn't. Every time we'd try and slow down, he'd still have some throttle on and you could just feel the car fight itself. We worked on it for a while, but he could not get off the gas (habit I guess). I made him right foot brake and changed nothing else. We almost spun twice on the first run because we had a lot more front grip but he was turning like he had been before. No other changes. So you need to make 1000% sure you aren't confusing things by dragging the brakes when on the gas, or dragging the gas when on the the brakes.
That said, just chaning tires can and will change the balance of a car. Tire pressures, alignment, bars, etc. etc.
Does taking grip from and end make a car faster? Only if you can't get the car balanced any other way.... My rule of thumb is simple. Maximize grip at both ends (including making sure the driver isn't causing the push if there is one) and tune from there.
I do think the car could use a little better balanced set of bars. I tend to use either a 35/22 combo like the Shelby has, and that I made a prototype set of that Jim in VA now has. I will also use the Hotchkis bars even though the rear is 1" which is normally bigger than I prefer. But I'm ok with it because the front bar from Hotchkis is much larger @ 1.5" so the balance remains good. Also both front and rear bars from the are hollow (most everyone else only runs a hollow front) and both bars are adjustable too. I also have bars from Hellwig, Eibach, H&R and Steeda, as well as the Hotchkis bars. Choices abound, but frankly H&R's rear is too big @ 26mm. Hellwig are both adjustable, but at this time both solid and the rear is 1" (again too big for the front they use IMHO).
03-26-2009, 06:01 PM
#6
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Thread Starter
Join Date: Feb 2007
Location: Texas
Posts: 162
You're going to hate this.... When does it understeer? All the time? Sometimes? On the way in? mid-corner? On the way out? What are you doing with your feet? I ask because I recall a long conversation in which I told you that using the brake and gas at the same time (he's a left footer and the car is an automatic) will confuse things.
Left foot braking cannot change the laws of physics. In fact, more to the point just last weekend I had a student in a C6 Corvette who's LFBing was just completely screwing him. There is nothing wrong with it *done correctly* and in fact in theory it's faster. But most don't do it correctly, and I recall in out conversation that there was something that led me to believe you were using it as a crutch. The man in the C6 told me he'd be doing it for 25 years and felt he was good at it. He wasn't. Every time we'd try and slow down, he'd still have some throttle on and you could just feel the car fight itself. We worked on it for a while, but he could not get off the gas (habit I guess). I made him right foot brake and changed nothing else. We almost spun twice on the first run because we had a lot more front grip but he was turning like he had been before. No other changes. So you need to make 1000% sure you aren't confusing things by dragging the brakes when on the gas, or dragging the gas when on the the brakes.
Just to make sure, the car is not an automatic. I shift from 3rd to 4th on the back and front straights at TWS. The rest of the track is taken in 3rd which means that I have about 10 corners where I don't have to downshift. I trail brake and using the left foot simply makes me smoother. The brake and gas are used together for maybe a 1/2 second - one is always coming off as the other one comes on.
Does taking grip from and end make a car faster? Only if you can't get the car balanced any other way.... My rule of thumb is simple. Maximize grip at both ends (including making sure the driver isn't causing the push if there is one) and tune from there.
I do think the car could use a little better balanced set of bars. I tend to use either a 35/22 combo like the Shelby has, and that I made a prototype set of that Jim in VA now has. I will also use the Hotchkis bars even though the rear is 1" which is normally bigger than I prefer. But I'm ok with it because the front bar from Hotchkis is much larger @ 1.5" so the balance remains good. Also both front and rear bars from the are hollow (most everyone else only runs a hollow front) and both bars are adjustable too. I also have bars from Hellwig, Eibach, H&R and Steeda, as well as the Hotchkis bars. Choices abound, but frankly H&R's rear is too big @ 26mm. Hellwig are both adjustable, but at this time both solid and the rear is 1" (again too big for the front they use IMHO).
I do think the car could use a little better balanced set of bars. I tend to use either a 35/22 combo like the Shelby has, and that I made a prototype set of that Jim in VA now has. I will also use the Hotchkis bars even though the rear is 1" which is normally bigger than I prefer. But I'm ok with it because the front bar from Hotchkis is much larger @ 1.5" so the balance remains good. Also both front and rear bars from the are hollow (most everyone else only runs a hollow front) and both bars are adjustable too. I also have bars from Hellwig, Eibach, H&R and Steeda, as well as the Hotchkis bars. Choices abound, but frankly H&R's rear is too big @ 26mm. Hellwig are both adjustable, but at this time both solid and the rear is 1" (again too big for the front they use IMHO).
As to where I am, (after adjusting the Koni's, stiffer in back than the front), the car turns in nicely and transitions back to steady state understeer on track out. I like the security blanket of the understeer as I still tend to lift, carefully, when I'm too hot.
I have five points left in NASA TTC, so I could consider bars, but I'm just mainly trying to understand how they work. I'm trying to keep the car as a CMC trainer and they don't allow bar changes, unless they were stock on some model (so no Shelby or Bullitt bars).
Edit to add: The real reason for the question is that whenever I see in-car camera shots, from almost any series, the driver seems to be constantly "catching" oversteer. So that tells me that maybe oversteer is fast. But is it fast if you have to "throw away" rear grip to get it?
-Wayne
Last edited by houstonnw; 03-26-2009 at 06:27 PM. Reason: additional question
03-26-2009, 06:21 PM
#7
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Sorry, I knew I remembered automatic.... None the less it doesn't matter *if* (and I'm saying if, not that you are) you are riding the brake in funny ways the car won't like it and the car will get tight.
Autox vs. track makes no nevermind here. A car at the limit is a car at the limit, and there are plenty of autocrossers proving that we're good on a track. And more to the point, a 45mph corner on a track is no different than a 45mph corner autoxing unless somehow you think the car reacts differently to a course defined by cones vs. grass.
You're asking what to do next, sort of, but I have no idea what the pressures are, what the alignment is, etc. What does the car do mid-corner. It turns in well and then understeers on the way out. That data helps, but what is the neutral throttle balance like? What if we loosen it up on the way out and then it's too loose in? And fwiw, Bullitt bars are the same as GT bars...
I don't know I have an answer for you. I don't much like theory, prefer reality. The reality is to help you tune the car better I need a lot more information on when/how it does what and what the other parameters are that could be effecting it. And again, a tire change could well change the cars behavior with no other changes. So I'd recommend getting on a tire you want to run and setting up for that.
Autox vs. track makes no nevermind here. A car at the limit is a car at the limit, and there are plenty of autocrossers proving that we're good on a track. And more to the point, a 45mph corner on a track is no different than a 45mph corner autoxing unless somehow you think the car reacts differently to a course defined by cones vs. grass.
You're asking what to do next, sort of, but I have no idea what the pressures are, what the alignment is, etc. What does the car do mid-corner. It turns in well and then understeers on the way out. That data helps, but what is the neutral throttle balance like? What if we loosen it up on the way out and then it's too loose in? And fwiw, Bullitt bars are the same as GT bars...
I don't know I have an answer for you. I don't much like theory, prefer reality. The reality is to help you tune the car better I need a lot more information on when/how it does what and what the other parameters are that could be effecting it. And again, a tire change could well change the cars behavior with no other changes. So I'd recommend getting on a tire you want to run and setting up for that.
03-26-2009, 06:41 PM
#8
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Thread Starter
Join Date: Feb 2007
Location: Texas
Posts: 162
Sorry, I knew I remembered automatic.... None the less it doesn't matter *if* (and I'm saying if, not that you are) you are riding the brake in funny ways the car won't like it and the car will get tight.
Autox vs. track makes no nevermind here. A car at the limit is a car at the limit, and there are plenty of autocrossers proving that we're good on a track. And more to the point, a 45mph corner on a track is no different than a 45mph corner autoxing unless somehow you think the car reacts differently to a course defined by cones vs. grass.
You're asking what to do next, sort of, but I have no idea what the pressures are, what the alignment is, etc. What does the car do mid-corner. It turns in well and then understeers on the way out. That data helps, but what is the neutral throttle balance like? What if we loosen it up on the way out and then it's too loose in? And fwiw, Bullitt bars are the same as GT bars...
I don't know I have an answer for you. I don't much like theory, prefer reality. The reality is to help you tune the car better I need a lot more information on when/how it does what and what the other parameters are that could be effecting it. And again, a tire change could well change the cars behavior with no other changes. So I'd recommend getting on a tire you want to run and setting up for that.
Autox vs. track makes no nevermind here. A car at the limit is a car at the limit, and there are plenty of autocrossers proving that we're good on a track. And more to the point, a 45mph corner on a track is no different than a 45mph corner autoxing unless somehow you think the car reacts differently to a course defined by cones vs. grass.
You're asking what to do next, sort of, but I have no idea what the pressures are, what the alignment is, etc. What does the car do mid-corner. It turns in well and then understeers on the way out. That data helps, but what is the neutral throttle balance like? What if we loosen it up on the way out and then it's too loose in? And fwiw, Bullitt bars are the same as GT bars...
I don't know I have an answer for you. I don't much like theory, prefer reality. The reality is to help you tune the car better I need a lot more information on when/how it does what and what the other parameters are that could be effecting it. And again, a tire change could well change the cars behavior with no other changes. So I'd recommend getting on a tire you want to run and setting up for that.
The real reason for the question is that whenever I see in-car camera shots, from almost any series, the driver seems to be constantly "catching" oversteer. So that tells me that maybe oversteer is fast. But is it fast if you have to "throw away" rear grip to get it?
Just curious why everybody else wants to "catch" oversteer all the time.
-Wayne
03-26-2009, 08:27 PM
#9
1st Gear Member
Join Date: Dec 2007
Posts: 100
I'll give you two reasons why I might give up grip at one end or the other:
#1 To balance the car. I find understeer frustrating and would prefer to "feel" like the car is balanced in steady state turns. Listening to the front tires scrub away doesn't do it for me. This doesn't necessarily make me faster, but it increases my enjoyment of driving.
#2 To rotate the car faster. I tend to like to get the car turned as quickly as possible and without the stiffer rear bar I had a real hard time doing that even with pretty heavy trail braking. Either I just didn't have the skill or the car wasn't up to the task.
Disclaimer: I'm no autocross champion, you should listen to Sam. And, I use street tires, not R-comps.
#1 To balance the car. I find understeer frustrating and would prefer to "feel" like the car is balanced in steady state turns. Listening to the front tires scrub away doesn't do it for me. This doesn't necessarily make me faster, but it increases my enjoyment of driving.
#2 To rotate the car faster. I tend to like to get the car turned as quickly as possible and without the stiffer rear bar I had a real hard time doing that even with pretty heavy trail braking. Either I just didn't have the skill or the car wasn't up to the task.
Disclaimer: I'm no autocross champion, you should listen to Sam. And, I use street tires, not R-comps.
03-26-2009, 08:40 PM
#10
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Join Date: Oct 2007
Location: Harrisburg PA
Posts: 1,778
I don't have anything to add regarding your question about throwing away grip, its a good question and I'm enjoying this discussion.
But I am kind of chuckling in a deja vue sort of way. Over on the Vette forum right now there is a thread going just like this but the other way around - trying to cure oversteer. The guy has done just about every trick in the book trying to change the characteristics and still having issues. He comes from the momentum car world and is frustrated with the C6.
The conclusion of many very knowledgeable folks in that forum is - he has to adjust his expectations and driving style. The car is an oversteerer and he has to learn to deal with it.
As for the Stang - it is inherently an understeering car, its in the DNA. I'm not suggesting you can't change handling characteristics, we all know we can, just that fundamentally its a front heavy, rear stick axle car.
Cheers. I'm going back to the b-ball game now, go Pitt!
But I am kind of chuckling in a deja vue sort of way. Over on the Vette forum right now there is a thread going just like this but the other way around - trying to cure oversteer. The guy has done just about every trick in the book trying to change the characteristics and still having issues. He comes from the momentum car world and is frustrated with the C6.
The conclusion of many very knowledgeable folks in that forum is - he has to adjust his expectations and driving style. The car is an oversteerer and he has to learn to deal with it.
As for the Stang - it is inherently an understeering car, its in the DNA. I'm not suggesting you can't change handling characteristics, we all know we can, just that fundamentally its a front heavy, rear stick axle car.
Cheers. I'm going back to the b-ball game now, go Pitt!