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

[blacksheep-1]

I wasn’t talking about springs….

Talking about your governor?

 

[blacksheep-1]

From the people I know and what I know from them of how Ford Racing Parts works I don't believe for a second that there was any testing involved other than "yeah, those fit".

IMO progressive springs have no place on the street either.

Yeah, I wish I knew a few of those guys..

 

[Fabman]

Talking about your governor?

That one comes to mind.

 

[ShifterX]

I'd wager a lot of what you're feeling for squat is down to the progressive springs. Frankly, I detest progressive springs in every way. If someone asked me to sort your car out the first thing I would do is go linear rate. Not try and tune around the progressiveness.

I would agree. Seems like all stock perch type springs are progressive rate. This makes comparing even the listed spring rates of springs more difficult.

These springs seem soft to me. But from the choices I had they were on the stiffer side. Looking for minimal drop in the front and about as stiff as possible. Open to suggestions. But it may be some trial and error.

Probably will hold off on messing with AS for now. The trailing arm angle does not seem extreme enough to mess with. Especially if the minimum drop is 2". I would not end up much any closer to horizontal.

 

[TeeLew]

The way I look at anti-dive and anti-squat is that you're changing how much weight transfer under braking or acceleration is happening through the suspension linkage vs the springs & shocks. If you have 100% anti-dive and anti-squat, then all the longitudinal weight transfer happens through linkages and none through springs & shocks. And it happens instantly. This means you can't use springs & shocks to tune handling during longitudinal weight transfer. Having less anti-dive & anti-squat means you can use your shocks to tune & time the longitudinal weight transfer, just as you can use shocks to tune & time lateral weight transfer (if the roll center isn't at CG). If you're using a "soft spring & big bar" style suspension, you can keep the dive & squat under control by running higher anti-dive & anti-squat percentages.

In broad brush-strokes, this is how I look at it. On a live rear car, when you start playing around much with drop brackets, then the roll-steer goes to hell and the added anti-lift introduces brake hop. The roll-steer is used *massively* on dirt oval modifieds. They measure it in inches...no sh*t....and use it to turn the car. It's really cool to sit down and have a conversation with those dudes. I just don't like it for road course stuff.

My first experience with playing with something like this was running Paul Brown's setup on my Fox way back. I had a summer job when I was in school mounting race tires. We were at the 1994 Des Moines Grand Prix and I stalked him down more as a fan than a customer, but I bought the bars with my per diem cash so I didn't seem weird.

I was completely sold on the concept of increasing anti-squat, mostly be reading Herb Adams book that was out at the time. His whole logic was massively flawed, but I didn't know any better. Anyway, I changed a lot at the same time with the arms because I was also going from a 7.5"/drum to 8.8"/disc rear end with the bigger GT discs on the front, etc.

After the change, the first thing I noticed was that it was easy to introduce brake hop. That's basically how I'd set bias. I'd turn the prop valve to the rear until I'd get hop and then go 1/2 a turn forward. More rear bias was definitely better for braking, and I was never in danger of locking the rears without the hop. Once the hop starts on entry, though, it can be a real b*tch to deal with the locking. Now add roll-oversteer as the roll builds in the corner, and the tail starts wagging the dog. Going to throttle was my normal response. It wouldn't necessarily fix the problems, but it would end the suspense. I would throw it off the road every once in a while rear-end first. In retrospect, I got away with a couple that could have been *real* ugly.

The one thing you always have with a live rear is camber control. You can't always allow all the roll you want with an independent rear because of geometry issues, but you can with a live. You also have very good control of your total toe-in across the axle for obvious reasons. Roll steer and anti-squat are both changing as we play with lower arm height. Roll steer works laterally and anti-squat works longitudinally, but they often increase or decrease together.

It's a tool. If increasing A/S allows you to run a little softer rear spring or turn the car earlier in the corner, then it's probably a good thing. It's definitely a case of diminishing returns, though. As soon as it starts introducing any instability or traction problems, then it's a liability.

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"A car is like a primate, it has to squat to go." - Carroll Smith

 

[TeeLew]

Off Topic.....

IDK how the track community as a whole feels about progressive rate springs.......but I HATE them.

There can be some good reason to stage springs (bump rubbers), but I'm no fan of progressives.

 

[blacksheep-1]

You guys knew it was coming
This is the gold standard for S197 suspensions right here...
Pole run at VIR back around 2016, I think this same car won the SPGP, the last pro win for the Boss302R platform.

 

[navseng]

In broad brush-strokes, this is how I look at it. On a live rear car, when you start playing around much with drop brackets, then the roll-steer goes to hell and the added anti-lift introduces brake hop. The roll-steer is used *massively* on dirt oval modifieds. They measure it in inches...no shiznit....and use it to turn the car. It's really cool to sit down and have a conversation with those dudes. I just don't like it for road course stuff.

My first experience with playing with something like this was running Paul Brown's setup on my Fox way back. I had a summer job when I was in school mounting race tires. We were at the 1994 Des Moines Grand Prix and I stalked him down more as a fan than a customer, but I bought the bars with my per diem cash so I didn't seem weird.

I was completely sold on the concept of increasing anti-squat, mostly be reading Herb Adams book that was out at the time. His whole logic was massively flawed, but I didn't know any better. Anyway, I changed a lot at the same time with the arms because I was also going from a 7.5"/drum to 8.8"/disc rear end with the bigger GT discs on the front, etc.

After the change, the first thing I noticed was that it was easy to introduce brake hop. That's basically how I'd set bias. I'd turn the prop valve to the rear until I'd get hop and then go 1/2 a turn forward. More rear bias was definitely better for braking, and I was never in danger of locking the rears without the hop. Once the hop starts on entry, though, it can be a real biznitch to deal with the locking. Now add roll-oversteer as the roll builds in the corner, and the tail starts wagging the dog. Going to throttle was my normal response. It wouldn't necessarily fix the problems, but it would end the suspense. I would throw it off the road every once in a while rear-end first. In retrospect, I got away with a couple that could have been *real* ugly.

The one thing you always have with a live rear is camber control. You can't always allow all the roll you want with an independent rear because of geometry issues, but you can with a live. You also have very good control of your total toe-in across the axle for obvious reasons. Roll steer and anti-squat are both changing as we play with lower arm height. Roll steer works laterally and anti-squat works longitudinally, but they often increase or decrease together.

It's a tool. If increasing A/S allows you to run a little softer rear spring or turn the car earlier in the corner, then it's probably a good thing. It's definitely a case of diminishing returns, though. As soon as it starts introducing any instability or traction problems, then it's a liability.

-------------------------------------------------------------------------------------------------------------------------------

"A car is like a primate, it has to squat to go." - Carroll Smith

AS is better adjusted with the top link though, and leaving the lowers level at ride height. Are you saying you had adjusted the AS with the lowers by having them run downhill (side view front to back) , then yeah, that could definitely cause some issues.

I'd still be curious about actual geometry of a race trim s197 where the actual numbers fall in, but no one seems to want to answer that question.

 

[blacksheep-1]

AS is better adjusted with the top link though, and leaving the lowers level at ride height. Are you saying you had adjusted the AS with the lowers by having them run downhill (side view front to back) , then yeah, that could definitely cause some issues.

I'd still be curious about actual geometry of a race trim s197 where the actual numbers fall in, but no one seems to want to answer that question.

Maybe no one has those answers, I'm sure some techy can come up with a computer simulation. Regardless of that, you're gonna have to make whatever you have, work. The S197 platform like a lot of ride height, and a lot of squat, and really weak springs.

 

[blacksheep-1]

There can be some good reason to stage springs (bump rubbers), but I'm no fan of progressives.

We used to keep several, in different viscosity, cut in half and full size.

 

[TeeLew]

AS is better adjusted with the top link though, and leaving the lowers level at ride height. Are you saying you had adjusted the AS with the lowers by having them run downhill (side view front to back) , then yeah, that could definitely cause some issues.

I'd still be curious about actual geometry of a race trim s197 where the actual numbers fall in, but no one seems to want to answer that question.

Well, on a Fox, the axle ends are splayed arms cast into the housing. The whole idea was a big mess and there was never any good way to deal with them except to bin them and use a torque arm/panhard setup. So you were painted into a corner unless you wanted to do some serious fab work. I was young and probably game to do it (God knows I sketched out several 3-link/watts ideas), but poor and when push came to shove, I put on the inexpensive bolt-on arms. The chassis point was a poly bush and the other end had a lowering bracket on the stock axle bucket with a big rod-end for the pivot.

 

[navseng]

Well, on a Fox, the axle ends are splayed arms cast into the housing. The whole idea was a big mess and there was never any good way to deal with them except to bin them and use a torque arm/panhard setup. So you were painted into a corner unless you wanted to do some serious fab work. I was young and probably game to do it (God knows I sketched out several 3-link/watts ideas), but poor and when push came to shove, I put on the inexpensive bolt-on arms. The chassis point was a poly bush and the other end had a lowering bracket on the stock axle bucket with a big rod-end for the pivot.

Ah ok, that makes sense i get it!

I had an sn95 in my younger days too with a similar setup and I did the ghetto 3 link (removing one of the links) with a home brew panhard . It was junk... Haha

Welding link mounts onto the cast section probably wouldn't be the best play..

 

[navseng]

Maybe no one has those answers, I'm sure some techy can come up with a computer simulation. Regardless of that, you're gonna have to make whatever you have, work. The S197 platform like a lot of ride height, and a lot of squat, and really weak springs.

I mean there are plenty of calculators out there its just some measurements you plug in. Just curious where the numbers fall in , that's all.

 

[RoadRacer78]

I would agree. Seems like all stock perch type springs are progressive rate. This makes comparing even the listed spring rates of springs more difficult.

These springs seem soft to me. But from the choices I had they were on the stiffer side. Looking for minimal drop in the front and about as stiff as possible. Open to suggestions. But it may be some trial and error.

Probably will hold off on messing with AS for now. The trailing arm angle does not seem extreme enough to mess with. Especially if the minimum drop is 2". I would not end up much any closer to horizontal.

You can run straight rate "coilover" springs from Viking, Hyperco, etc in the rear paired with UPR adjustable spring perches (the aluminum ones). This allows you to pick whatever straight rate spring you want and be able to set ride height wherever you want it to. I run this combo in everything now. Including my drag car.

Billet Lowering Rear Ride Height Adjuster Kit (fits 05-14 Mustang) UPR

Set the rear ride height of your 05-13 Mustang with UPR Products Adjustable Rear End Spring Mount. These mounts weld to the factory lower spring perch on the rear end and feature a Billet Aluminum adjuster that allows up to 3" of adjustability.

www.uprproducts.com

Viking 10 Inch 2.5 inch Diameter Coil Over Spring

Viking ultra lightweight, high travel 10" springs. 25% weight savings over some other brands on the market. Made in the USA from high tensile spring steel with a sleek silver or black powder coated finish and length/spring rate clearly marked on each spring. Cold wound, heat treated and shot...

www.uprproducts.com

 

[ShifterX]

You can run straight rate "coilover" springs from Viking, Hyperco, etc in the rear paired with UPR adjustable spring perches (the aluminum ones). This allows you to pick whatever straight rate spring you want and be able to set ride height wherever you want it to. I run this combo in everything now. Including my drag car.

Billet Lowering Rear Ride Height Adjuster Kit (fits 05-14 Mustang) UPR

Set the rear ride height of your 05-13 Mustang with UPR Products Adjustable Rear End Spring Mount. These mounts weld to the factory lower spring perch on the rear end and feature a Billet Aluminum adjuster that allows up to 3" of adjustability.

www.uprproducts.com

Viking 10 Inch 2.5 inch Diameter Coil Over Spring

Viking ultra lightweight, high travel 10" springs. 25% weight savings over some other brands on the market. Made in the USA from high tensile spring steel with a sleek silver or black powder coated finish and length/spring rate clearly marked on each spring. Cold wound, heat treated and shot...

www.uprproducts.com

More thinking about the front, where with spring has to fit the factory style upper and lower mounts. Limited options with the stock style springs. It seems like most anything with a high rate has significant lowering (+1.5" drop). Like H&R or MM race springs.

Trying to keep the front geometry near stock. Target is 15" hub to fender which is about 3/4" drop. During my first search for springs, I read some great posts from @Norm Peterson. He advocated for the BMR GT500 handling springs because of the minimal drop in the front (on a GT) and the relatively stiff straight rate of 260lbs. They are pretty cheap too. That's the route I plan to go.

For anti-squat, I am going with the idea that a 1" trailing arm rise is better than a 1" trailing arm drop. At least for now.

 

[RoadRacer78]

More thinking about the front, where with spring has to fit the factory style upper and lower mounts. Limited options with the stock style springs. It seems like most anything with a high rate has significant lowering (+1.5" drop). Like H&R or MM race springs.

Trying to keep the front geometry near stock. Target is 15" hub to fender which is about 3/4" drop. During my first search for springs, I read some great posts from @Norm Peterson. He advocated for the BMR GT500 handling springs because of the minimal drop in the front (on a GT) and the relatively stiff straight rate of 260lbs. They are pretty cheap too. That's the route I plan to go.

For anti-squat, I am going with the idea that a 1" trailing arm rise is better than a 1" trailing arm drop. At least for now.

I just put a set of those BMR springs on my shop "bang for the buck" 3v street car yesterday (over Bilsteins). It's got the UPR adjusters/ perches and 200# Viking springs out back. I'm curious how it's going to sit once it's on the ground. Being a street car I don't care that much about ride height and it's effects on performance. It will still go around corners pretty fast. But if it sits too low I'll make some spacers for the strut mounts to bring it back up.

It's only got 26" tires on it. I don't think it could look too low.

 

[blacksheep-1]

Well, on a Fox, the axle ends are splayed arms cast into the housing. The whole idea was a big mess and there was never any good way to deal with them except to bin them and use a torque arm/panhard setup. So you were painted into a corner unless you wanted to do some serious fab work. I was young and probably game to do it (God knows I sketched out several 3-link/watts ideas), but poor and when push came to shove, I put on the inexpensive bolt-on arms. The chassis point was a poly bush and the other end had a lowering bracket on the stock axle bucket with a big rod-end for the pivot.

We weren't allowed to change the suspension points, but we could add a panhard bar. ( installing a PHB with the triangulated 4 link was death, you might as well weld up the suspension, it was in such a bind) HOWEVER... the rules said nothing about bushing material, so we used poly bushings on 3 of the 4 links and roll bar padding on the 4th, basically allowing the PHB to center the diff, and freeing up the entire POS so it would work... sort of.
Details of the poor man's 3 link can be found under the sn95 header, it was one of the first posts. I think it was called the junkyard dog.

 

[SMGDHG]

It's not a very intelligent answer but WILL answer your question:

Buy RLCA relocation brackets (ones with multiple holes) and try them in each hole. This is something you can change in ~10mins trackside.

You'll feel a big difference between the two extremes. There are pros and cons to each extreme. This is a good way to feel and learn the impacts of anti-squat %

 

[Fabman]

It's not a very intelligent answer but WILL answer your question:

Buy RLCA relocation brackets (ones with multiple holes) and try them in each hole. This is something you can change in ~10mins trackside.

You'll feel a big difference between the two extremes. There are pros and cons to each extreme. This is a good way to feel and learn the impacts of anti-squat %

Boom.

 

[TeeLew]

We weren't allowed to change the suspension points, but we could add a panhard bar. ( installing a PHB with the triangulated 4 link was death, you might as well weld up the suspension, it was in such a bind) HOWEVER... the rules said nothing about bushing material, so we used poly bushings on 3 of the 4 links and roll bar padding on the 4th, basically allowing the PHB to center the diff, and freeing up the entire POS so it would work... sort of.
Details of the poor man's 3 link can be found under the sn95 header, it was one of the first posts. I think it was called the junkyard dog.

I've read about people doing this since. At the time, all I really knew was that it was a handful to drive no matter what I did. The SN95 didn't exist when I was polishing my '79 Indy Pace Car turd. I had decided that understeer was the enemy and so anything that made me saw on the wheel more must be fast. At the very least, it was both an entertaining and educational time.

Side note: Understeer is *not* the enemy.