Trying to Learn squat....

[Mad Hatter]

Ok, so I have a bunch or articles spinning around in my head.... and I just got in from under the car measuring the uca and lca angles....

This is what I got so far...



My UCA is at stock length and in the upper of three positions on the car (what a pain to install). The LCA is in the middle position. Both UCA and LCA are BMR gear.

If I am trying to add a little more squat (less antisquat), I could raise the LCA to the upper position of three. and/or lower the rear suspension a little to move the instant center further forward??

If I did both, the intersection would be below the neutral line and the instant center would be further forward. Should I be aiming to intersect closer to the center of gravity??

Am I on the right track? or .... I don't just know SQUAT!

couldn't resist that!!

 

[Mad Hatter]

Something more like this too Squat??

 

[VoodooBoss]

Rob knows squat.

@blacksheep-1

 

[Grant 302]

I used to know squat...

And I'm not trying to be cryptic here, because I haven't set up a road course car with the intent to increase it...

...but I think you have to consider the effects of roll and the different left-right geometry that you'll have when exiting a turn. I think you'd need to have the inside side still in squat as the rear tire droops/inside quarter lifts. Like visualizing the arms during roll-steer conditions.

Look at your spring rates and how much travel it will take to transfer the ~1,000 lbs off the inside front and mostly transfer to the outside rear. Might help to get a jack under one of the front corners and see. That won't be exactly the same, but will give you an idea of the dynamic positions.

I'll try to find some of my track pics that you can see the lower trailing arms. I know I have something showing the outside.

 

[blacksheep-1]

Well, and maybe AJ will jump in here, we pretty much use the stock attacjment points, also, squat, rate of squat, depend a lot on those shocks and their adjustments...It's a system and we use a ton of squat but those guys wrench like mad men on the car to get it right, even coming in. making a change and going right back out. My suggestion, as it usually is, is to quit redesigning the suspension system, duplicate the T1 or T2 car and drive it.

 

[Mad Hatter]

I downloaded the Scca rules to see what a T1 or T2 car is limited too. Thats a big file! My first race is at the end of March so hope to get some track time to test this all out! Mean time will set the LCA basically in horizontal.. But the UCA is at a fairly steep angle and a real PIA to get too for adjustments. Guess I have to check the pinion angle after every change angle ajustment..! Its just me and two dogs....no pit crew!

So for the next track test I will leave the cars as follows

 

[Grant 302]

Not the best pics, but part of what I was mentioning earlier.

Outside T10 Chuckwalla:


Inside T16 Chuckwalla:


The main thing to notice is how different those two angles are and that the inside trailing geometry is very well into anti-squat territory. My static angle is ~3º +/- up to the front of the car. This is all planned/designed to prevent the inside from going much if any downward even at full compression.

I *think* your static lower trailing arm static angle probably needs to be pointing *down* to the front to get what you're looking for. Even if just slightly so that under full droop on the inside, that that side is dynamically under "100% anti-squat" (I dislike those terms, btw...but they are convention). Maybe even like 1" or more difference in pivot point heights. Again, I don't know because I've never set up a car to do this intentionally even though I've spent waaaaay too much time thinking about it over the years.

Secondary effects from roll-steer using parallel lower trailing arms should also help in theory. Roll understeer would point the outer rear wheel toward centerline and further help weight transfer to that corner.

As for your upper trailing arm connection point, I *think* the lowest connection would be best. But that's more of a guess. You have the BMR mount with the 3 siamesed holes?

 

[Fabman]

I made this video quite a while back (you may have seen it) to see what the trailing arms did under actual track conditions. Set with a static angle of 1* up at full race weight.
Upon viewing the video I noticed that the car spent much of it's time with the trailing arms on the wrong part of the curve, so I was able to make adjustments based on real data.
There are two different views of the suspension in action. This is Laguna so most of the turns are to the left.

This is just a visual to give perspective to static settings, dynamically.

https://www.facebook.com/video.php?v=10155155104213535

 

[BigTaco]

 

[Mad Hatter]

Thanks for all the input... I do have the BMR three hole bracket, so I will try the the highest position and see what happens on the track.

Reading Fabmans previous posts again, Interesting how everything gets changed around as you go too stickier tires and more HP. With square 275 street tires and the LCAs at horizontal, the roll understeer was very pronounced while cornering. Going to a higher angle brought roll oversteer that improved my lap times (with that setup). Now with a little more HP and lots more R7 295 grip, things get turned around. What was working great on street tires is not so optimal on slicks and a better suspension. Or at least thats what I intend to find out!!

To be more specific my goal is to go faster. I would love to able to list the inside front tire probably because of a long time love affair with Alfas. I always wanted to have a 1970 vintage Alfa GT.

 

[Fabman]

Thanks for all the input... I do have the BMR three hole bracket, so I will try the the highest position and see what happens on the track.

Reading Fabmans previous posts again, Interesting how everything gets changed around as you go too stickier tires and more HP. With square 275 street tires and the LCAs at horizontal, the roll understeer was very pronounced while cornering. Going to a higher angle brought roll oversteer that improved my lap times (with that setup). Now with a little more HP and lots more R7 295 grip, things get turned around. What was working great on street tires is not so optimal on slicks and a better suspension. Or at least thats what I intend to find out!!

To be more specific my goal is to go faster. I would love to able to list the inside front tire probably because of a long time love affair with Alfas. I always wanted to have a 1970 vintage Alfa GT.

Cortex recommends lower trailing arm to be 3* to 5* up at race weight.

 

[ajaquilante]

SCCA T2 rules require OEM pickup points and OEM control arms except as permitted. They allow the Ford Racing rear lower control arms with poly bushings and the Ford racing adjustable panhard bar. Also allowed is the FR upper rear shock mount to use eye-to-eye rear shocks and move the springs to the shock in a coil over. The cars are not slammed to the ground. Actually probably pretty close to OEM ride-height considering the diameter of tire is much smaller.

SCCA T1 is OEM pickup points, and control arms are open, coilovers open. We used Ford racing rear lower control arms with sphericals, FR Panhard bar.

The honest truth is that we never have measured or tried to calculate anything. #1, not allowed to move anything, and #2.When we got into the Mustangs, FR already had good baseline setups. We adjusted springs, shocks and bars from there.

Like every other company out there, we could sell you a kit of parts and your car would be able to do exactly as ours does. You want that inside wheel in the air and rear end planted on the ground? What tire do you run and what size, and how is the track lay out, as that will determine how much wheel lift you get. The only difference between "their" parts and ours, is that I know what ours will do and how the car feels. Now is that necessarily better? Not totally because different drivers like different things, but so far, we've maybe only had one that couldn't wrap their head around driving a Mustang the fast way.

Now there is nothing wrong with trying to learn about the dynamics of the car. If you have the money and time go for it. I just caution that with the internet a lot of opinions can be given without a good way to quantify the findings. That is what I like about racing in series with tighter rule books vs track-days and "open" competitions, it removes a lot of "this is better because"...

One thing that was reiterated to us during our brief stint with the running PorscheGT3's , The first engineer wanted to move this and move that, while the replacement engineer told us to put everything back to the way Porsche designed it. Why? because if moving this and that was so beneficial, wouldn't Porsche have done that when designing their racecar in the first place? Same can be said for Ford, if moving this mount, or changing that mount was so easy and so beneficial, then why didn't they change it on the FR500C, FR500S, 302R, 302S?

 

[Mad Hatter]

thanks Fabman my LCA angle is currently at 3.5 degrees.

I wish our racing was with a few more rules.. but its pretty much open season for us with cars ranging from all out racer cars to exotics and then a few semi street cars like mine. Doing the best possible with out going ballistic with costs will be my aim.

Luckily I have gotten to the point that my best race day lap times are seldom off by more then 0.5sec. So I should be able to register any improvements in the car with the changes I have made and am planning to make (hopefully!!).

Some time ago I did buy a Ford Racing LCA and brackets and dug it out of storage the other day just in case the BMR positions did not fit. Would put it on now, but want to see how the new UCA and spherical bearings work first so as not to confuse myself even more!

One of the reasons I went with the Cortex coilovers (simple Koni shocks) is that the Ford P springs were too low for me after a year, was scraping the ground all the time even without a full load of race tires and tools etc. I don't have the car slammed at all. My race tire size is 295/30-18 R7s square with a 25" wheel diameter. So the cars sits a inch lower just with the tires.

Looking back at how I got the car to this point.... Its easy to see how you would do things differently! Going a SCCA T1 route would make lots of sense since you guys already charted the way forward.

Never the less....Happy with the car, certainly like driving it....The one thing that has me a little worried is the current UCA angle of 15 degrees seems a bit steep, looks like a little wrench gymnastic will be required to make it longer...

 

[Fabman]

SCCA T2 rules require OEM pickup points and OEM control arms except as permitted. They allow the Ford Racing rear lower control arms with poly bushings and the Ford racing adjustable panhard bar. Also allowed is the FR upper rear shock mount to use eye-to-eye rear shocks and move the springs to the shock in a coil over. The cars are not slammed to the ground. Actually probably pretty close to OEM ride-height considering the diameter of tire is much smaller.

SCCA T1 is OEM pickup points, and control arms are open, coilovers open. We used Ford racing rear lower control arms with sphericals, FR Panhard bar.

The honest truth is that we never have measured or tried to calculate anything. #1, not allowed to move anything, and #2.When we got into the Mustangs, FR already had good baseline setups. We adjusted springs, shocks and bars from there.

Like every other company out there, we could sell you a kit of parts and your car would be able to do exactly as ours does. You want that inside wheel in the air and rear end planted on the ground? What tire do you run and what size, and how is the track lay out, as that will determine how much wheel lift you get. The only difference between "their" parts and ours, is that I know what ours will do and how the car feels. Now is that necessarily better? Not totally because different drivers like different things, but so far, we've maybe only had one that couldn't wrap their head around driving a Mustang the fast way.

Now there is nothing wrong with trying to learn about the dynamics of the car. If you have the money and time go for it. I just caution that with the internet a lot of opinions can be given without a good way to quantify the findings. That is what I like about racing in series with tighter rule books vs track-days and "open" competitions, it removes a lot of "this is better because"...

One thing that was reiterated to us during our brief stint with the running PorscheGT3's , The first engineer wanted to move this and move that, while the replacement engineer told us to put everything back to the way Porsche designed it. Why? because if moving this and that was so beneficial, wouldn't Porsche have done that when designing their racecar in the first place? Same can be said for Ford, if moving this mount, or changing that mount was so easy and so beneficial, then why didn't they change it on the FR500C, FR500S, 302R, 302S?

Back in the day guys would move stuff all over (illegally) not knowing what they were doing and screw up all the geometry. I used to tell them: "There is way more speed in the correct wheel rates than there is for all the cheatin' in china".
Translation: Fine tune the basics first, then experiment if you're so inclined.

 

[ChrisM]

SCCA T2 rules require OEM pickup points and OEM control arms except as permitted. They allow the Ford Racing rear lower control arms with poly bushings and the Ford racing adjustable panhard bar. Also allowed is the FR upper rear shock mount to use eye-to-eye rear shocks and move the springs to the shock in a coil over. The cars are not slammed to the ground. Actually probably pretty close to OEM ride-height considering the diameter of tire is much smaller.

SCCA T1 is OEM pickup points, and control arms are open, coilovers open. We used Ford racing rear lower control arms with sphericals, FR Panhard bar.

The honest truth is that we never have measured or tried to calculate anything. #1, not allowed to move anything, and #2.When we got into the Mustangs, FR already had good baseline setups. We adjusted springs, shocks and bars from there.

Like every other company out there, we could sell you a kit of parts and your car would be able to do exactly as ours does. You want that inside wheel in the air and rear end planted on the ground? What tire do you run and what size, and how is the track lay out, as that will determine how much wheel lift you get. The only difference between "their" parts and ours, is that I know what ours will do and how the car feels. Now is that necessarily better? Not totally because different drivers like different things, but so far, we've maybe only had one that couldn't wrap their head around driving a Mustang the fast way.

Now there is nothing wrong with trying to learn about the dynamics of the car. If you have the money and time go for it. I just caution that with the internet a lot of opinions can be given without a good way to quantify the findings. That is what I like about racing in series with tighter rule books vs track-days and "open" competitions, it removes a lot of "this is better because"...

One thing that was reiterated to us during our brief stint with the running PorscheGT3's , The first engineer wanted to move this and move that, while the replacement engineer told us to put everything back to the way Porsche designed it. Why? because if moving this and that was so beneficial, wouldn't Porsche have done that when designing their racecar in the first place? Same can be said for Ford, if moving this mount, or changing that mount was so easy and so beneficial, then why didn't they change it on the FR500C, FR500S, 302R, 302S?

AJ, do you use the Multimatic upper arm and stock differential bushing in your cars? I'm not sure what they came with.

 

[ajaquilante]

Back in the day guys would move stuff all over (illegally) not knowing what they were doing and screw up all the geometry. I used to tell them: "There is way more speed in the correct wheel rates than there is for all the cheatin' in china".
Translation: Fine tune the basics first, then experiment if you're so inclined.

Exactly. I can understand before computers and simulation design, but in today's world with computer design and sim work, along with much better manufacturing tolerances, I'm not sure you can get magical gains. With the GS/PWC cars, we were fine tuning spring rates with 15 lb/in spring rubbers.

AJ, do you use the Multimatic upper arm and stock differential bushing in your cars? I'm not sure what they came with.

Nope. Only used it once on the GS car. Went back to the OEM arm after one race in 2013. Always used the OEM diff bushing.

 

[Fabman]

Exactly. I can understand before computers and simulation design, but in today's world with computer design and sim work, along with much better manufacturing tolerances, I'm not sure you can get magical gains. With the GS/PWC cars, we were fine tuning spring rates with 15 lb/in spring rubbers.

This was the 80's and early 90's....right around the dawn of the cell phone and before. The only computer we had seen at that point was on star trek...thats how old I am. I used to draw out chassis and suspension layouts on the floor in chalk at 1-1 scale and swing the arcs with a string and a pencil. It was archaic, but it worked and it was more than a lot of others would do so that put me at the head of the curve....sad as that is.

I have a set of those spring rubbers.
Back in the day we used twist in coil spring spacers. "Knuckle busters" we called them.
Now everybody has a software program to do the thinking for them....progress I suppose.

 

[blacksheep-1]

down south we call those"goobers"..
we call adjustable wrenches the " fitall wrench".
Like " throw a couple of goobers in that spring and hand me the fitall wrench"
you guys need to get on board.

 

[Fabman]

down south we call those"goobers"..
we call adjustable wrenches the " fitall wrench".
Like " throw a couple of goobers in that spring and hand me the fitall wrench"
you guys need to get on board.

All the good racing info came from the south....the saying was always:
"Well the guys down south are all doing....."
I acquired the transcript from a chassis seminar from a notable builder way back when and it really accelerated my understanding. I had always been a vociferous reader of all things racecar, but the southern boys really had a way of making sense of things.

 

[Grant 302]

Back in the day we used twist in coil spring spacers. "Knuckle busters" we called them.
Now everybody has a software program to do the thinking for them....progress I suppose.

I knew them as 'spring helpers'. Used them in the 80's and got them from J.C. Whitney, IIRC. Used them for cars that squat too much on the strip...like a poor man's air bag. Sometimes just on the right side.

I understood what you were talking about when you mentioned 'spring rubbers' a while back. Looks like they've evolved a lot since I've used anything like that. I'm sure they're a lot softer. But I'd caution that their effect on a 5 coil spring is a lot greater than 8 or more coil springs that you might have been using them on in the past.