Suspension Talks: Understeer & Oversteer

[svxistentialist]

Gentlemen

This Forum benefits from the knowledge, skill and opinions of a variety of talented and professional people. Some of this experience is experiential like Trevor's skill as a driver, which I do not doubt for one minute. Some of the expertise we enjoy comes directly from engineering knowledge and I also have no doubts about the bona fides of many contributors, in particular Harvey's credentials, or Shotgunslade's.

I don't want this particularly informative thread to degenerate into a slagging match between individuals. Nor am I going to be piggy-in-the-middle between a Harvey and Trevor confrontation again.

For the most part this discussion on SVX handling and driving technique has been carried on in what Trevor sometimes calls "robust discussion". In a robust discussion disagreements will happen and sarcasm may creep in, that's people for ya. However in post #54 Trevor is going over the line regarding Harvey's engineering credentials. That's disrespect, is against the rules, and there was no need for it.

This is such a good discussion otherwise there is no way I want to close the thread. But if you all continue to behave like children in a schoolyard I will close it or one of the mods will close it, reluctantly.

Grow up.

Joe

[icingdeath88]

Furthermore, keep in mind guys that much is lost in translation, when it comes to discussion of many things over the internet. I think it's very likely that if you were talking in real life, with a car handy to describe exactly what you're talking about, it would go much more nicely, and you'd find much more common ground than you've found. So take it easy.

[Trevor]

Originally Posted by svxistentialist

Gentlemen

This Forum benefits from the knowledge, skill and opinions of a variety of talented and professional people. Some of this experience is experiential like Trevor's skill as a driver, which I do not doubt for one minute. Some of the expertise we enjoy comes directly from engineering knowledge and I also have no doubts about the bona fides of many contributors, in particular Harvey's credentials, or Shotgunslade's.

I don't want this particularly informative thread to degenerate into a slagging match between individuals. Nor am I going to be piggy-in-the-middle between a Harvey and Trevor confrontation again.

For the most part this discussion on SVX handling and driving technique has been carried on in what Trevor sometimes calls "robust discussion". In a robust discussion disagreements will happen and sarcasm may creep in, that's people for ya. However in post #55 Trevor is going over the line regarding Harvey's engineering credentials. That's disrespect, is against the rules, and there was no need for it.

This is such a good discussion otherwise there is no way I want to close the thread. But if you all continue to behave like children in a schoolyard I will close it or one of the mods will close it, reluctantly.

Grow up.

Joe

Joe,

I have had a gut full of you and your clique continually backing Harvey and preventing me from defending myself against his snide nasty remarks. You conveniently ignore that which commenced the issue, i.e. Harvey's post #54. ---

“Dan when you go out on a real track, and race in a real race, like Trevor has, you will find out all about it. Harvey.”

A sly sarcastic insult, which directly mentions me by name, and which absolutely breaks the rules because it constitutes baiting. What is more it absolutely records disrespect by innuendo.

When I defended myself with this honest and direct statement, all hell brakes loose. ---

“Harvey, as always your crappy posts are based on nothing but sarcasm. I have been their and done it. There is no shame in saying so when posting relative information. You by contrast claim engineering status without the required credentials.”

N.B. I now make a direct complaint that Harvey’s post constitutes baiting as is clearly stated within the rules.

I do not expect within this forum to be to be arrogantly told, --- “But if you all continue to behave like children in a schoolyard I will close it or one of the mods will close it, reluctantly. --- Grow up.”

Joe, you have thrown a greasy spanner in the works and as far as I am concerned the thread is closed. Prior to you sticking your oar in, there was not a problem. You have completely spoiled an interesting technical thread, which has involved several in much time and effort. I am having careful second thoughts as to the value of the network.

[shotgunslade]

I also would like to protest Trevor's condescending and often insulting style. Our skirmish in this thread started when I said that my SVX responded well to trail braking, a common technique taught extensively in the Skip Barber School. Trevor called that term an "invented reference", despite the fact that it is discussed at length in "Going Faster", the Skip Barber School textbook by Carl Lopez. This reverence was dismissed with "Forget racing schools, they are for playboys with a big cheque book." After that it just got ugly, on both sides.

But here are my points, and I stand by them despite Trevor's convoluted and, I think disparaging, harangue.

1. To get an SVX to rotate to help negotiate a turn, continue braking after turn in, rather than turning-in without brakes and immediately beginning to squeeze the accelerator.

2. Braking in the SVX while turning will tighten the turn, acceleration, while turning, will straighten out the turn. In a rear wheel drive car, if significant acceleration is initiated while cornering near the limit, the additional forward forces transmitted through the rear tires, will reduce their ability to transmit lateral forces, so that the rear end will come around and "rotate" the car.

3. The faster way through a corner in an SVX is to carry more speed into and through turn-in than you would in a rear wheel drive car, and to use the rotation that you get from "trail braking" to help get you in to the corner apex.

4. Apply full acceleration only after you begin to track-out, letting the wheel slowly go back to straight. This may occur slightly before or at the apex. By no means should full acceleration be applied well before the corner apex while you have the greatest amount of wheel angle for the corner. Acceleration will unweight the front end of the car, and your car will just "push," and front tire scrubbing will waste much of your applied power and diminish front lateral grip.

5. An effective means of negotiating a hairpin turn in the SVX is to turn in sharply under hard braking, which will cause the rear end to come around an appreciable amount, so that the car very quickly is pointed almost in the direction of the corner exit. Then apply full accelerator as you allow the car to track out. I have gained several car lengths through hairpin corners in this fashion.

6. If these principles are applied, the SVX is very predictable and enjoyable, and in fact, easy to drive on the track.

7. None of these techniques requires grass cutting to explore the limits of the car.

8. You don't need to participate in cut-throat racing to enjoy driving the SVX fast. Improvement of my technique and reduction of my lap times is sufficient for me. I have nothing to prove. I just want to have fun.

So, why does my recitation of these simple ideas incite Trevor to say:

My guess is that you have not properly interpreted what you have been told, and your instructor thank god, has not been game to sit along side you when you drive close to the limit. I commiserate with him.

Very often when members of this forum make remarks about driving or car dynamics, Trevor jumps in to pontificate, broadcast his experience in bombastic language, and insult and dimish the other forum members. His arrogant treatment of Tony in the endless "SVX Engine cooling "Again & Again" is a good example. Tony was working his butt off, making modifications and testing ideas, eventually, through experimentation, giving some good new insights into a pervasive problem. Trevor's contribution to this thread was an endless stream of indecipherable, yet combative posts, contributing almost nothing. I think that by the end of that thread, most members had figured out how to deal with Trevor, just ignore his posts completely. He may well have vast experience, and significant driving skills, but his antagonistic and condescending style diminishes my enjoyment of this forum and the value of his information. I'm sure Trevor would say: "Well, you're always free to leave and don't let the door bang your ass on the way out."

Let's just put it this way, only a very small portion of my experience in this forum is unpleasant. I guess the best way to overcome that problem is to "ignore completely" that one small source of unpleasantness.

In reflection, I apologize for having gotten sucked into this harangue.

Breaking news -- This just in -- Important progrss on this issue "I am having careful second thoughts as to the value of the network." Stay tuned.

[Crazy_pilot]

Originally Posted by SilverSpear

Well you have to dismantle the hell out of the front suspension to do that. But if I am not mistaken you do it only once in a lifetime.

Unfortunately it's not even that easy. The front bar runs through a hollow in the subframe. Without a 2-piece construction it is literally impossible to install it. I've puzzled over it a few times and can't come to an easy solution.

I do have one idea that might be possible. If the arms of the front bar were shortened to end in front of the axle, a tab could be welded onto the leading edge of the control arm to act as the end-link connection. The bar itself would be no thicker or stiffer (it's the stock bar), but due to the shorter arms it's effectiveness would be increased. The benefit would be mitigated slightly by the location of the tab on the control arm, as it's location closer to the pivot point gives the arm more leverage against the bar.

Measuring the relative stiffness of the bar is quite simple. The bar is laid on a table with the end of one arm clamped in place and the other overhanging the end of the table. Weight is hung from the free end and the deflection angle is measured. By plotting the load/deflection of on bar against the other it is possible to create a direct static comparison.

[TomsSVX]

front bar is cake... Seperate the two pieces at the splined end. Remove the support bushings and brackets, slide it through the subframe... Might even be able to do with the tires on

Tom

[Crazy_pilot]

That's my point. The 2-piece set-up is uber-easy. I have taken it out with the wheels on, although it was on a drive on hoist and I could get underneath the car. To make a new bar in a one-piece setup would be nigh impossible to install.

[Trevor]

Originally Posted by shotgunslade

I also would like to protest Trevor's condescending and often insulting style. Our skirmish in this thread started when I said that my SVX responded well to trail braking, a common technique taught extensively in the Skip Barber School. Trevor called that term an "invented reference", despite the fact that it is discussed at length in "Going Faster", the Skip Barber School textbook by Carl Lopez. This reverence was dismissed with "Forget racing schools, they are for playboys with a big cheque book." After that it just got ugly, on both sides.

But here are my points, and I stand by them despite Trevor's convoluted and, I think disparaging, harangue.

1. To get an SVX to rotate to help negotiate a turn, continue braking after turn in, rather than turning-in without brakes and immediately beginning to squeeze the accelerator.

2. Braking in the SVX while turning will tighten the turn, acceleration, while turning, will straighten out the turn. In a rear wheel drive car, if significant acceleration is initiated while cornering near the limit, the additional forward forces transmitted through the rear tires, will reduce their ability to transmit lateral forces, so that the rear end will come around and "rotate" the car.

3. The faster way through a corner in an SVX is to carry more speed into and through turn-in than you would in a rear wheel drive car, and to use the rotation that you get from "trail braking" to help get you in to the corner apex.

4. Apply full acceleration only after you begin to track-out, letting the wheel slowly go back to straight. This may occur slightly before or at the apex. By no means should full acceleration be applied well before the corner apex while you have the greatest amount of wheel angle for the corner. Acceleration will unweight the front end of the car, and your car will just "push," and front tire scrubbing will waste much of your applied power and diminish front lateral grip.

5. An effective means of negotiating a hairpin turn in the SVX is to turn in sharply under hard braking, which will cause the rear end to come around an appreciable amount, so that the car very quickly is pointed almost in the direction of the corner exit. Then apply full accelerator as you allow the car to track out. I have gained several car lengths through hairpin corners in this fashion.

6. If these principles are applied, the SVX is very predictable and enjoyable, and in fact, easy to drive on the track.

7. None of these techniques requires grass cutting to explore the limits of the car.

8. You don't need to participate in cut-throat racing to enjoy driving the SVX fast. Improvement of my technique and reduction of my lap times is sufficient for me. I have nothing to prove. I just want to have fun.

So, why does my recitation of these simple ideas incite Trevor to say:



Very often when members of this forum make remarks about driving or car dynamics, Trevor jumps in to pontificate, broadcast his experience in bombastic language, and insult and dimish the other forum members. His arrogant treatment of Tony in the endless "SVX Engine cooling "Again & Again" is a good example. Tony was working his butt off, making modifications and testing ideas, eventually, through experimentation, giving some good new insights into a pervasive problem. Trevor's contribution to this thread was an endless stream of indecipherable, yet combative posts, contributing almost nothing. I think that by the end of that thread, most members had figured out how to deal with Trevor, just ignore his posts completely. He may well have vast experience, and significant driving skills, but his antagonistic and condescending style diminishes my enjoyment of this forum and the value of his information. I'm sure Trevor would say: "Well, you're always free to leave and don't let the door bang your ass on the way out."

Let's just put it this way, only a very small portion of my experience in this forum is unpleasant. I guess the best way to overcome that problem is to "ignore completely" that one small source of unpleasantness.

In reflection, I apologize for having gotten sucked into this harangue.

Breaking news -- This just in -- Important progrss on this issue "I am having careful second thoughts as to the value of the network." Stay tuned.

You continue to very conveniently misinterpret all I have said, “convoluted and, I think disparaging, harangue.” is a personal misconception.

(1) Above. As I have pointed out, please when making a statement, first indicate the degree of “turn” called for in the change of direction involved. A serious corner can not be approached without heavy braking, at which point the car should be set up before entry. N.B. I note that it is now agreed that the accelerator is squeezed, rather than slammed.

(2) Assuming that a US SVX is involved and there is front drive bias during cornering, front wheel drive technique should apply. If so acceleration during turn in will increase the front slip angle and the car will understeer.

In a rear wheel drive car only an idiot driver would induce a spin out whereby, ---- “significant acceleration is initiated while cornering near the limit, the additional forward forces transmitted through the rear tires, will reduce their ability to transmit lateral forces, so that the rear end will come around and "rotate" the car.”

The throttle is used to balance the car as per the photo above. Where have I indicated that the car should be deliberately spun out?

(3) Both a front and rear drive car with road tyres should be set up for the corner before entry and the attitude carried through the corner without brakes. A car fitted with sticky racing type tyres, involves a completely different approach to driving and this is area which is being covered by your instructor. What is more, as you are only involved for fun, he is not advising you how to drive on the limit on road tyres.

(4) You are stating that things should be allowed to happen during cornering. I state that the car should be set up on entry so that things happen in accordance with your requirements throughout the manoeuvre. The driver should dictate the attitude of the car. He should not respond after the fact, and be called upon to correct what need not have occurred.

(5) Just where have I disagreed with your current statement?

(7) If you have not exceeded the limits, you have not explored the limit and are not aware of the limit. You are not seriously extending the limit. You now advise that you are only involved in having fun. Why raise an argument regarding an issue beyond and not involved with, what you have personally exoerienced?

(8) If proper motor racing is not your cup of tea so be it. As a result you should not be insisting that your views are authoritative. I held RAC, Federation International de L'Automobile racing drivers license No, FIA 5829, valid worldwide and only granted as a result of demonstrated experience. Even so I am flexible when it comes to techniques involving sticky tyres, a topic completely outside of that covered here.

In have in no way been incited. By contrast you have become excited, as a result of being disagreed with. As I have previously pointed In many respects there is no real disagreement, only confusion relating to the degree of cornering involved. The instructor is teaching you how to very safely drive around a circuit at speed.

I have been referring to serious motor racing, whereby one must travel as quickly as is possible, while overtaking other cars in the process. I would now appear that you have been involved in no more than trials against the clock.

If the thread and your posts are examined fairly, it will be seen that it is you who have overreacted and I have done no more that counter your incisive remarks.

It is unfortunate that you regard decisive English as being bombastic. I find it desirable in order to accurately relate technical information. Your use of the word “slammed” is a case in point.

My contribution to the “Cooling again and again” thread, involved the the presentation of what was deemed correct. The fact that it was contrary to that recorded by the author, and therefore was taken by those without understanding who could nor decipher what was involved, is not my concern. As yet no one has proven that the modifications covered within the thread are proven effective overall.

If the thread is examined carefully, it will be seen that I expressed special respect for Tony and phrased every post accordingly. What is more you did not have access to exchanges of personal messages. I reject your nasty insinuations.

I have been advised by PM, that in circumstances such as this, I should resort to clicking the complaints button, but I refrain from doing so. You and others with your views do not concern me. Rattle your dags.

Your sarcastic insertion, --- “Breaking news -- This just in -- Important progrss on this issue "I am having careful second thoughts as to the value of the network." Stay tuned.”

I have recently been advised by the clique, that this, your sly form of attack, falls within the rules. All of this emphasises exactly why I am having second thoughts regarding this place.

P.S. I note that your current post within the thread, SVX Engine cooling again & again, confirms that the overall modifications covered by the thread, and in particular those to which I have specifically referred, have not been applied. Therefore your nasty statement regarding my contribution to the thread, is devoid of fact.

[SilverSpear]

Originally Posted by Crazy_pilot

Unfortunately it's not even that easy. The front bar runs through a hollow in the subframe. Without a 2-piece construction it is literally impossible to install it. I've puzzled over it a few times and can't come to an easy solution.

I do have one idea that might be possible. If the arms of the front bar were shortened to end in front of the axle, a tab could be welded onto the leading edge of the control arm to act as the end-link connection. The bar itself would be no thicker or stiffer (it's the stock bar), but due to the shorter arms it's effectiveness would be increased. The benefit would be mitigated slightly by the location of the tab on the control arm, as it's location closer to the pivot point gives the arm more leverage against the bar.

Measuring the relative stiffness of the bar is quite simple. The bar is laid on a table with the end of one arm clamped in place and the other overhanging the end of the table. Weight is hung from the free end and the deflection angle is measured. By plotting the load/deflection of on bar against the other it is possible to create a direct static comparison.

Yeah I was just checking a diagram and you might be right at this. The front bar is too much of a hassle for sure, but I guess it is worth it. With the heavy nose of the SVX, a better anti roll bar is a must and I am willing to go the extra mile to do it.

Here is a diagram:



Now if you check the picture, and a recapitulation:
- Front bar has funky bents and it is shaped as L + I
- 18mm thickness, same as the rear.
- It passes through a subframe, hence the shape as L + I.

Ideas:
1- What if a blacksmith was able to make the same funky shapes but instead of L + I it would be a long L and in 24mm? Then after sliding it through the subframe he can heat it up at the point of the driver side bushing and bend it to become a U ?

2- Remove the entire subframe and do the same above mentioned job..

What worries me most is not what I mentioned above, but rather a competent blacksmith who can do all those shapes on a 24mm (or so) bar.

Thoughts?

[Trevor]

Originally Posted by SilverSpear

Ideas: ----
What worries me most is not what I mentioned above, but rather a competent blacksmith who can do all those shapes on a 24mm (or so) bar.

Thoughts?

How about sliding piece of hardened steel tubing over the bar, drilled with several holes, so that through these it can be spot arc welded at intervals on a radius, along the bar. Obtaining suitable tubing could present difficulties, but it could be worth investigating. A blacksmith will advise what could be possibly be hardened/tempered.

It would be a matter of trial and error to test if the existing links and arms will cope with extra load. However road cars are usually over engineered, so that it is reasonable to be optimistic.

[shotgunslade]

Reacting only to substantive portions of a previous post.

The issue of trail braking (braking to assist cornering) is a controversial issue. At the Bertil Roos school, it was highly discouraged. At the Panoz school, it was discussed as an advanced strategy that they would not be getting into. I know that at the Skip Barber School, it is encouraged, although I have not attended that school.

Perhaps some of the confusion does spring from different language usage. In the US, "rotation" does not mean spinning, it means decreasing cornering radius due to controlled drift of the rear tires. Even a slight lateral slip that might occur from cresting a hill, especially when enhanced by a momentary throttle lift can serve to assist cornering through car "rotation." The car is actually rotating around an axis likely somewhere near its outside front tire. The degree of rotation may only be a few degrees, but it can really assist getting around the corner. Achieving this is easier in a rear wheel drive car, because you can use the throttle to accelerate thereby expending some of the available traction of the rear tires, and reducing the available lateral traction.

The description of this phenomenon in "Going Faster", is really clear. It is described as the "friction circle." It really helps understanding of the relationship of the forces transmitted through the tire contact patches.

One thing I have seen, is that finding and hitting the apex of the corner is importnat, but also, the direction the car is pointing at the apex is also important. The more the car is pointed toward the ultimate direction of the exit from the corner, the less cornering is left to be done after the apex, and the safer and more effective will be full acceleration after that point. The SVX seems to benefit from a later turn-in, as long as it doesn't tighten the corner too much, a later apex, and the slight rotation from trail braking. With that technique, when you brush the inside track edge at the apex, you will be pointed more directly toward the corner exit.

[svxistentialist]

Originally Posted by Trevor

How about sliding piece of hardened steel tubing over the bar, drilled with several holes, so that through these it can be spot arc welded at intervals on a radius, along the bar. Obtaining suitable tubing could present difficulties, but it could be worth investigating. A blacksmith will advise what could be possibly be hardened/tempered.

It would be a matter of trial and error to test if the existing links and arms will cope with extra load. However road cars are usually over engineered, so that it is reasonable to be optimistic.

I think this plan of Trevor's could work, but from the look of that diagram the lateral bar is not 100% straight, it has two minor bends in it. This will complicate the shape of the hollow tube, perhaps require 3 hollow tubes to be tacked on.

Another suggestion would be to only grow the lateral part of the front sway bar.

You see where the LHS [on the right in the drawing] of the bar is screw threaded to allow bolting on the curly side? This is for ease of fitment because it has to go through the hole in the subframe. If you were making a complete new unit what would stop you cutting and threading it at both ends? That would allow you to make the centre longest lateral section thicker in diameter and bolt on the two bendy bits at either side.

For simplicity you might even consider using the current thickness of the two curly ends, with the centre lateral of greater thickness. It will still create greater resistance to torque than standard.

Worth trying?

Joe

[SilverSpear]

Originally Posted by Trevor

How about sliding piece of hardened steel tubing over the bar, drilled with several holes, so that through these it can be spot arc welded at intervals on a radius, along the bar. Obtaining suitable tubing could present difficulties, but it could be worth investigating. A blacksmith will advise what could be possibly be hardened/tempered.

It would be a matter of trial and error to test if the existing links and arms will cope with extra load. However road cars are usually over engineered, so that it is reasonable to be optimistic.

How can I slide these on a bar with curves more than a living snake?

[shotgunslade]

Is the left lateral bar symmetrical? If so, then a 3 piece bar might be easy to do as Joe has suggested. Fabricate a thicker center section without the integral right arm, and attach a left lateral arm to each end, both the left and the right.

[SilverSpear]

Originally Posted by shotgunslade

Is the left lateral bar symmetrical? If so, then a 3 piece bar might be easy to do as Joe has suggested. Fabricate a thicker center section without the integral right arm, and attach a left lateral arm to each end, both the left and the right.

No they are not. Check the diagram above.

Furthermore, how can you attach a thicker bar (6~7 more mm?) to 18mm arms? You sure need a hell of a machinist to mate them correctly. I prefer not to go this route though, I still believe a continuous bar like the rear is the best way for it.

I will need a high resolution photo of the front bar of an SVX, will show it to both a machinist and a blacksmith. Let me see what they have to say about this.

Now another issue, if the rear is the bontrager with a 22mm diameter. What should be installed in the front? 23? 24? 25?

I sneaked into Bill's locker, he is using 25mm if I am not mistaken. But isn't this too much?