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

[RoadRacer78]

If you go with the later 19mm ball joints you’ll need to bore the spindle to fit them. I have a fixture that I use to align them in the mill so the holes are straight. I also clamp a small piece of material in the slot so the cut isn’t interrupted which could break the cutting tool. Or you could just buy the later 19mm spindles. The Howe kit is a Chrysler screw in ball joint body. Much beefier with a weld on bung. These are widely used on race cars.

The ball joints aren't going to be customer friendly. So that's a no go. The masses need to be able to throw the past at the car from across the room and they install themselves. I can't believe how much push back I get from the customer base when it comes to setting things up. Correctly set pinion angle? "I didn't do that and my car is fine". Correctly shim the slave cylinder? "I didn't do that and my car is fine". Correctly set up belt tension on a blower car. "I didn't do that and my car is fine". I doubt they would feel the same if their engine builder put their motor together without measuring anything.....

 

[Fabman]

The ball joints aren't going to be customer friendly. So that's a no go. The masses need to be able to throw the past at the car from across the room and they install themselves. I can't believe how much push back I get from the customer base when it comes to setting things up. Correctly set pinion angle? "I didn't do that and my car is fine". Correctly shim the slave cylinder? "I didn't do that and my car is fine". Correctly set up belt tension on a blower car. "I didn't do that and my car is fine". I doubt they would feel the same if their engine builder put their motor together without measuring anything.....

Theres an old racers saying: "Winners do what Losers won't".
This is why you see the same people/teams rising to the top while others continually flounder.

 

[DaveW]

Yeah, I live in that world too which is why I got away from parts selling and just do part installing.

I have never verified, but it seems like the word on the street has always been that a B6 has pretty high compression valving, certainly more than a Ford/Tokico. Could that be shocking the tire more on the GT causing the wheelspin? I have no idea, just know that when my car is close overall in setup but gets on a site with less/more traction, I can make a pretty significant change in middle/exit traction with a click or 2 of compression adjustment. It's really a band aid type of shock adjustment, but works quickly and doesn't effect anything else.

 

[RoadRacer78]

Yeah, I live in that world too which is why I got away from parts selling and just do part installing.

I have never verified, but it seems like the word on the street has always been that a B6 has pretty high compression valving, certainly more than a Ford/Tokico. Could that be shocking the tire more on the GT causing the wheelspin? I have no idea, just know that when my car is close overall in setup but gets on a site with less/more traction, I can make a pretty significant change in middle/exit traction with a click or 2 of compression adjustment. It's really a band aid type of shock adjustment, but works quickly and doesn't effect anything else.

That is a possibility. I'd have to drive both cars while really paying attention to what's going on to verify.

 

[TeeLew]

Set your car up with zero anti squat and get back to us with the results.

Are you arguing with me or Newton?

For the record, if it's on a car, I've probably used it at some point on a setup. On a particularly slick track with a traction limited car, I've run pro-squat in the rear suspension. It works fine. It's just one of a million spices in the soup.

It sounds like you have a lot of differences between the two cars, even if the engines are the same. The dampers are going to be a huge difference and the bars will probably be meaningful as well.

 

[TeeLew]

I have no idea, just know that when my car is close overall in setup but gets on a site with less/more traction, I can make a pretty significant change in middle/exit traction with a click or 2 of compression adjustment. It's really a band aid type of shock adjustment, but works quickly and doesn't effect anything else.

It's not a band-aid. You're matching the damping to the conditions. The same track will want somewhat different setting based on conditions, 100%.

 

[stevbd]

Are you arguing with me or Newton?

@TeeLew Interesting discussion. I think adjusting anti squat changes the vertical force on the rear tires - and thus grip - that is created when you apply engine torque. Low AS creates an upward force that pulls the tire away from the pavement when you apply torque and high AS creates a downward force that drives the tire into the pavement. The opposite happens under braking. In this manner increasing AS increases rear grip under acceleration and reduces it under braking. This is separate and apart from the other usual vehicle weight transfers that come with accelerating, turning, or braking.

 

[RoadRacer78]

Are you arguing with me or Newton?

I'm not arguing with you at all. In the same way that I don't argue with flat earthers. It's not worth my time.

 

[RoadRacer78]

@TeeLew Interesting discussion. I think adjusting anti squat changes the vertical force on the rear tires - and thus grip - that is created when you apply engine torque. Low AS creates an upward force that pulls the tire away from the pavement when you apply torque and high AS creates a downward force that drives the tire into the pavement. The opposite happens under braking. In this manner increasing AS increases rear grip under acceleration and reduces it under braking. This is separate and apart from the other usual vehicle weight transfers that come with accelerating, turning, or braking.

Exactly right.

An example of this would be the two basic drag car setups. A great example because a drag car has one job.

If you have a drag car that is set up for bias ply tires which are generally slicks you will have it set up with 90-100% AS. This is due to the sidewall of the tire being very soft and you want a little wheel speed (spin) out of a slick as it leaves the line. Dead hooking slicks doesn't work with their basic design.

If you take that same car and put drag radials on it you need to add AS until you have between 145-175%. This is because a drag radial has much stiffer sidewalls than slicks do so it requires more force to deform the tire correctly. And because of that stiff sidewall design you don't want very much or even little wheel speed. When a drag radial unhooks they tend to just "blow off". Their stiff sidewalls and sticky compounds make them light switches.

 

[TeeLew]

@TeeLew Interesting discussion..... This is separate and apart from the other usual vehicle weight transfers that come with accelerating, turning, or braking.

That's where we have our misunderstanding. Total weight/load transfer is determined by a few things and suspension geometry isn't one of them. Lateral/Longitudinal acceleration, track widths, wheelbase, C.G. height and position are the variables of interest. Springs, bars and geometry will influence the timing of how things happen, but it won't change the total amount. There is no real deflection in suspension links so the loads are transmitted very quickly from the contact patch to the chassis. The body has to actually start moving (roll or pitch) before the springs have an influence. Similarly, the car has to roll before the ARB's have an influence. The inertia of the sprung mass gives us a meaningful delay of the load transfer which goes through the elastic bits (springs/bars).

Loads in the suspension links are not separate from the other usual weight transfers which come from lat. or long. acceleration. The lateral and longitudinal accelerations are what drives and determines total amount weight/load transfer. Our choices of springs, bars, dampers and geometry will determine how those loads are distributed. These things will share the load in various percentages depending on the combination.

Herb Adams wrote a book about 35 years ago where he goes into detail about how anti's give you some extra load over and above the weight of the car. He was wrong, but I think this is where this idea comes from. IMO, he was a bit of a d!ck as well.

Here's my caveat: Drag strip launches are a place where you can momentarily get extra load on the tires with A/S suspension geometry. When applying the throttle on a road course, from 0-100% takes roughly 1 second with some average car on some average corner. The car will squat, but the motion of the chassis happens in a relatively controlled manner and it's small. The total motion of the body will be limited. On a drag launch, you get all the power at once. When the sprung mass starts to rotate around the CG (front up / rear down), then the actual physical movement of the mass will unload the tires. Because of this, you can crank up the A/S to reduce the physical motion of the sprung mass and minimize the momentary unloading of the tire due to theis chassis motion. Some cars have enough A/S that they'll push the rear of the car up initially, like a cat arching it's back. What you're trying to do in this scenario is time the loading through the suspension and the springs to load the tire as hard as possible, but, more importantly, avoid a chassis rebound which will unload the suspension in the moments after the launch and give wheelspin. Having said all this, drag racing is not my thing and I don't know the A/S numbers that are common for people to run at the strip. I do know it's a lot.

Anti-squat on the longitudinal axis is similar to roll-center height on the lateral axis. Have you tried the extended front ball-joints that raise the front roll center? Did it quicken the steering response of the car and flatten roll? It did, didn't it? It did so by supporting a small amount more of the lateral load transfer through the suspension links than before. This is the vertical component of the lateral loads being put into the chassis. If you kept raising it, you would eventually be taking all the lateral load in the suspension links and would have no compliance in the suspension. Mechanical grip would be very poor, but input reaction would be instant. This is the exact same with A/S. It's a way to distribute a portion of the longitudinal load transfer through the suspension links based on the horizontal force at the contact patch, but to do this, you ask more of the tire laterally. Raising the front roll center has the tendency to increase steering response, but also increase understeer later in the corner. Sometimes the added response is worth it and sometimes it's not.

But this is always true: If your car weighs 4000#, at any point of flat track around the lap (crests, compressions & banking will be neglected), if you could 'freeze frame' the car and put scales under the tires, it would always add to up to 4000#. It might be heavy on the front during braking, heavy on one side in a corner or heavy on the rear during acceleration, but it will always sum to 4000. You can't make higher than that unless you are physically shoving the sprung mass into the air like a hydraulic hopper. Even then it will only be momentary and quickly followed by being completely unloaded. The 'average' over the time period will still be 4000.

Does this help explain things?

 

[TeeLew]

I'm not arguing with you at all. In the same way that I don't argue with flat earthers. It's not worth my time.

Really, guy? Are you fkcing serious?

 

[stevbd]

But this is always true: If your car weighs 4000#, at any point of flat track around the lap (crests, compressions & banking will be neglected), if you could 'freeze frame' the car and put scales under the tires, it would always add to up to 4000#. It might be heavy on the front during braking, heavy on one side in a corner or heavy on the rear during acceleration, but it will always sum to 4000. You can't make higher than that unless you are physically shoving the sprung mass into the air like a hydraulic hopper. Even then it will only be momentary and quickly followed by being completely unloaded. The 'average' over the time period will still be 4000.

Does this help explain things?

@TeeLew I agree with most of what you are saying but respectfully, I think you may be conflating the force of the usual weight transfers of the car itself, which are created as a result of accelerating, braking, and turning the weight and mass of the vehicle, with the vertical forces on the rear tires that are created by applying torque to the rear tire either via the engine or brakes through the rear link geometry. As to the second, depending on rear geometry and anti-squat percentages, when you apply torque it creates a forward force arrow that makes the car move forward but it also creates a smaller and separate vertical force arrow (created by the engine torque, not the rearward transfer of the weight of the car) which depending on AS setup will either tend to drive the tire downward into the pavement or upwards off the pavement. Whichever way the vertical force arrow goes under torque from the engine, it will go the other direction under torque coming from the brakes. Which is why people running a lot of AS often complain about rear brake hop. So it's a compromise like everything. My understanding is that this upward or downward force is different and separate from the usual weight transfers you are describing (very well I would add).

At least that is how I understand it. I don't think I'm wrong but maybe I am and if I say more I will be out of my depth on this subject if I'm not already!

EDIT - I should add, this is my understanding of how a SRA S197 works with AS. Is AS even a thing with the IRS on an S550? I really don't know.

 

[RoadRacer78]

Really, guy? Are you fkcing serious?

Until Fabman tells me that anti squat has ZERO effect on traction, yes, I'm as serious as a heart attack.

 

[RoadRacer78]

EDIT - I should add, this is my understanding of how a SRA S197 works with AS. Is AS even a thing with the IRS on an S550? I really don't know.

IRS cars do have some anti squat characteristics. But it's a small faction of what a live axle car does.

 

[TeeLew]

Until Fabman tells me that anti squat has ZERO effect on traction, yes, I'm as serious as a heart attack.

If *that* is what you got out of what I wrote, then can I suggest re-reading it?

 

[RoadRacer78]

then can I suggest re-reading it?

No. I'm way past done with you.

 

[TeeLew]

@TeeLew As to the second, depending on rear geometry and anti-squat percentages, when you apply torque it creates a forward force arrow that makes the car move forward but it also creates a smaller and separate vertical force arrow (created by the engine torque, not the rearward transfer of the weight of the car) which depending on AS setup will either tend to drive the tire downward into the pavement or upwards off the pavement.

This is the torque reaction of the rear axle and, yes, it creates a spreading force between the sprung and unsprung masses separate of the vehicle acceleration. Having said that, it's basically pulling itself up by it's boot-straps. The forces are internal to the system. It doesn't add to the overall total weight of the car. The load it puts on the rear it takes off the front.

The only way to increase total load is with aerodynamics.

Yes, independent rears have anti-squat on drive and anti-lift while braking. They don't have to deal with the drive or coast torque reaction, so much less prone to brake hop.

 

[RoadRacer78]

If *that* is what you got out of what I wrote, then can I suggest re-reading it?

This is me extending an olive branch.

If you are not debating the pro "anti squat has no effect on traction" position what are you debating? More specifically, how can you be debating anything else with me? The only solid position I have taken is that anti squat has an effect on traction.

 

[TeeLew]

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.

 

[Fabman]

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.

This is my setup exactly.
Let the differential be free enough to articulate and put the power down while the competition is still trailbraking. Too much anti squat shocks the tires loose and binds up the suspension links making it artificially stiff. Low rear roll center, soft springs and bars (often w/no bar) Zero roll steer.
Now I am just an ammature engineer and can't explain things as elaquently as @TeeLew and some other really smart guys that visit these pages, but I have been very successful with this strategy.
Yes you pay for it with understeer, so season to taste.
Recently I backed the bite down just enough to help with rotation and the car was a rocket.
After all this time I'm Still learning.