S197 Anti Squat Numbers/ Theory/ Real World Results/ Etc

[blacksheep-1]

Which, BTW , is the reason a lot of very competitive guys are running a stock upper trailing arm. Corner entry, corner exit are the S197's really strong suites, center corner, not so much, so getting power down as much as possible, without shocking the tires, is paramount.

 

[stevbd]

@TeeLew damm, I would like that post 2x if I could. Super helpful and I learned a ton. Your second paragraph is a light bulb for me, especially the part about how AS adds rear roll stiffness under throttle. It makes perfect sense but I never thought of it. I was always wondering, if this thing has more grip why is it oversteering more when I try to get on the gas?

 

[stevbd]

Recently I backed the bite down just enough to help with rotation....

@Fabman what do you mean by this phrase? Thanks.

 

[Fabman]

@Fabman what do you mean by this phrase? Thanks.

I loosened the car up a tad. Gave up a tiny bit of traction for a better rotation.

 

[TeeLew]

I loosened the car up a tad. Gave up a tiny bit of traction for a better rotation.

Which is a great position to be in.

 

[Fabman]

Which is a great position to be in.

It all about balance.
A little more slip angle is just what I needed.

 

[TeeLew]

@TeeLew I was always wondering, if this thing has more grip why is it oversteering more when I try to get on the gas?

Glad I could help.

FWIW, I went through this exact exercise myself a long time ago with an aftermarket Fox lower trailing arm kit (Paul Brown). I just couldn't understand why if I'd done something to add grip why I was now fighting brake hop and saving my ass every time I turned the steering wheel. Something seemed wrong, but I knew adding anti-squat added grip. Tires must be old? (Let's face it, tires *were* old, mismatched with the front and probably used when I got them.)

Then I was in on building a Formula SAE car in school using the same idea. It didn't have sh!t for traction, either. At least that was adjustable. That was my first real lesson that something was happening which I didn't understand. Since then, I've had a lot of opportunities to learn how it all works together. There are probably other ways of looking at it, but my walls of text describe the model in my head.

 

[RoadRacer78]

I'm saying that it has an effect, but that adding anti-squat does not necessarily mean adding traction. In a lot of road race scenarios, it can hurt traction. The exact same impulse to the tire that we both agree can be beneficial on a drag car can hurt traction on a road race car because it feeds the load to the tire quicker than the tire can accept it. You end up 'blowing through' the tire. It's often referred to as the car 'feeling on the top of the road' and leads to a lot of partial throttle drifting. This would be the excess condition, but directionally, this is what increasing anti-squat does. If you've got a spicy tire that *wants* that sort of energy input, then by all means, it's a tool to use. Normal people don't get to run those tires.

Where adding anti-squat comes in handy is when you've got good traction, but the car is rolling/squatting enough on throttle that it's creating U/S out of low-speed corners, but you don't want to raise rear spring rate because of bumps. In this scenario, adding anti-squat will effectively add stiffness with throttle application and it has the effect of helping to turn the car on-throttle. This effect can be big when dealing with the torque reaction as well as the acceleration. Throw some roll steer in as well if you want to really make it turn.

It's all going to be a compromise. Let's say going up on the anti-squat means you can drop the spring 25#, maybe that's a option that does increase rear grip. For sure, with the power being talked about here, we're never going to be in this 'really good traction out of slow corners' situation. In this scenario, you start biasing the car for rear grip, which means soft bars, soft springs and get the geometry out of it (Lower the panhard bar and reduce anti-squat). Yes, it will squat and understeer more. It doesn't matter, because it'll be driving straight down the track while everyone else is busy sliding laterally out to the exit curb. The first guy to be able to go full throttle will be the fastest around a lap. Corner minimum speed is highly overrated.

___________________________________________________________________________________________
To loop all the way back to the start, you were talking about 50% anti-squat. I mentioned that I thought that was on the high side. For whatever reason, it was poorly received.

It's silly to think we can only talk about suspension after providing racing resumes. That's just an argument from authority. There are no perfect answers, only compromises. I'm just here to talk about the physics and share a bit of experience. You may very well come up with a better mousetrap than me, and that's an opportunity for us both to learn.

I see where this fell apart.

-I'm talking about the macro. You're talking about the micro.

-I'm not talking about roadrace cars. I'm talking about a good street car setup. There is no micro involved.

-I'm working on very, very basic "swings" at the suspension. You're getting into the nitty gritty (not a bad thing) but it just doesn't apply to street cars. They can't be pushed hard enough for the nitty gritty to matter.

-When it comes to AS specifically I'm just talking about the fact that it does have an effect on traction and to a lesser degree how the car feels and behaves. I have a car at approx 35% and another at approx 75%. I want to feel what 50% feels like so I have a "butt dyno database" of what the pros and cons of each is. I'm not necessarily looking for a "solution". I'm looking for information. Once I have that information I can come to a conclusion on what is going to be ideal for a street car and it's different set of requirements than a track car. Street cars that will generally have a LOT more power than track cars too. The setup direction is going to be quite different between a 500hp/400tq (at high RPM) track car and a 750hp/750tq (at lower RPM) street car. Those are two completely different animals in two completely different situations.

When you started debating me I couldn't figure out what was going on. I wasn't making claims. I wasn't suggesting one thing is better than another. I didn't see any basis for debate other than you were saying anti squat doesn't have an effect on traction. Which is the only thing I ever claimed as fact. All I was hearing (not necessarily what you were trying to say) was that you were saying anti squat has no effect on traction and you were coming after me directly.

 

[RoadRacer78]

@TeeLew

Now that we are maybe on the same page. If you were solving/testing for my "problem" which is where to set the AS% on a 750hp/750hp TQ street car that is only driven on the street. But driven as hard as can be on the street. What would your suggestion be?

 

[RoadRacer78]

It's silly to think we can only talk about suspension after providing racing resumes. That's just an argument from authority. There are no perfect answers, only compromises. I'm just here to talk about the physics and share a bit of experience. You may very well come up with a better mousetrap than me, and that's an opportunity for us both to learn.

I don't agree with this even a little bit. In these days of social media almost everyone talks and acts like they're an expert. When in fact you would be lucky if 1% of the people with opinions has ever walked the walk. This goes for all subjects. The only way to weed out the unqualified is to have the bonafides of the people commenting. I'm not targeting you with this statement. But when people say that you shouldn't have to provide a resume, bonafides, etc all I hear is someone without those things throwing up a smoke screen.

It is not an argument from authority. It as an argument of competence. Competence does not necessarily mean authority.

I also don't agree that there are no perfect answers when talking about engineering/ performance. Sure, the perfect answer is made up of compromises. But there is a best solution for everything. It can be tested.

This dovetails into opinion. I don't think opinion has any place in engineering. It either works, or doesn't work as intended. It can be measured.

 

[TeeLew]

-I'm not talking about roadrace cars. I'm talking about a good street car setup.

-When it comes to AS specifically I'm just talking about the fact that it does have an effect on traction and to a lesser degree how the car feels and behaves. I have a car at approx 35% and another at approx 75%. I want to feel what 50% feels like so I have a "butt dyno database" of what the pros and cons of each is. I'm not necessarily looking for a "solution". I'm looking for information. Once I have that information I can come to a conclusion on what is going to be ideal for a street car and it's different set of requirements than a track car. Street cars that will generally have a LOT more power than track cars too. The setup direction is going to be quite different between a 500hp/400tq (at high RPM) track car and a 750hp/750tq (at lower RPM) street car. Those are two completely different animals in two completely different situations.

I approach a road car setup very similarly to how I approach the setup of a car for FP1 on a street circuit, Cautiously. I make it relatively soft (still stiff compared to stock) to get over the nasty bumps you're going to find and with lots of rear grip, because I'm fine with having a bit of understeer in a car that might have have to deal with oil, water, gravel or whatever at the apex of a blind corner.

A 750/750 car on the street is a little bit like Barry Wood in the bedroom. You've got more under the hood than you can effectively use. I'd give it a lot of rear tire, soften the rear springs and do my best to not show up on a YouTube video while leaving Cars and Coffee.

As far as the A/S goes, by all means, if you've got options, try them out. If anything, it's educational. I suspect less than 35% would improve traction in general use, but maybe not for a stoplight launch. You'll have to rely on your butt dyno or Draggy for that.

 

[TeeLew]

when people say that you shouldn't have to provide a resume, bonafides, etc all I hear is someone without those things throwing up a smoke screen.

Just because I listen to someone doesn't mean I'll agree with them. I'll listen to just about anyone, but I believe damned few. Most of the time, when people brag about all the stuff they've done, I find it to be a way to avoid the actual engineering of the matter and make pronouncements from on high. On the other hand, if a guy were to actually have the resume and then keep it to himself, it makes things a little more conversational and doesn't end with, "Well, I've done X,Y, Z, so I know best!"

 

[Ludachris]

Guys, before I go through and do some thread cleanup, let it be known that these replies are not within the spirit of the forum. Please be respectful, even through disagreements.

 

[Mad Hatter]

What is it about talking squat?? Seems to be that only this topic, some people get overheated.

 

[Fabman]

What is it about talking squat?? Seems to be that only this topic, some people get overheated.

I remember.

 

[blacksheep-1]

I remember.

Not me,I don't run any of that stuff..

 

[Fabman]

Not me,I don't run any of that stuff..

He's referring to a certain someone who loved to fight about everything....the last battle was about anti squat.

 

[TeeLew]

Guys, before I go through and do some thread cleanup, let it be known that these replies are not within the spirit of the forum. Please be respectful, even through disagreements.

It's all good.

 

[TeeLew]

What is it about talking squat?? Seems to be that only this topic, some people get overheated.

Ya, who would have guessed that "Tire pressures at Daytona" was on the bingo card, either, but here we are.

 

[ShifterX]

What is it about talking squat?? Seems to be that only this topic, some people get overheated.

In some ways that’s what makes the s197 a more interesting foundation. It’s easier to change some of the engineering of suspension design than on typical irs cars.

I guess that can also be a downside as people throw parts at cars and end up creating more problems than solving.