antisquat %, IC height & length discussion - S197 mustang

lindertw

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So I went to the above website and was going to plot my suspension and am unsure about "Control arm LENGTH is not the actual length. It is the parallel/projected length along the horizontal axis."

Is it bolt hole to bolt hole or?

the control arm will be at an angle depending on where you have it installed on relocation brackets. take a plumb bob at each bolt and mark the spot on the floor front/rear. measure the distance on the floor (it will be a fraction of an inch shorter than the actual control arm length).

pythagorean.jpg
 
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psfracer

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I really like post #8. If we can get enough data I will make this a sticky. Great info so far.

Thanks for clarifying above. I would have measured from the center of each bolt hole to get the length.
 

Norm Peterson

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Not lowered, all OE geometry. Use it as a baseline with anybody's all-OE short times. From my own spreadsheet.

FWIW, antisquat will vary slightly due to driver weight. With a 180-ish lb driver aboard a car with OE springs and geometry the antisquat drops by about 1%. It won't necessarily be the same 1% for other configurations.

All dimensions not specified as lengths are co-ordinates, so control arm lengths are calculated internally

X = longitudinal (fore-aft)
Y = lateral (lateral angularity - it makes a small enough difference in these cars that it can be ignored for antisquat calcs)
Z = vertical

2008 Mustang OE (approx)

INPUTS
LCAchassisX . . . . . . . . . . .18.38in
LCAchassisY . . . . . . . . . . .23.63in
LCAchassisZ . . . . . . . . . . .7.88in

LCAaxleX . . . . . . . . . . . .0.00in
LCAaxleY . . . . . . . . . . . .22.13in
LCAaxleZ . . . . . . . . . . . .8.25in

CGHeight . . . . . . . . . . . .21.00in
Wheelbase . . . . . . . . . . . .107.10in
RearTireRollingRadius . . . . . . 13.00in

UCAchassisX . . . . . . . . . . .8.50in
UCAchassisY . . . . . . . . . . .0.00in
UCAchassisZ . . . . . . . . . . .19.38in

UCAaxleX . . . . . . . . . . . . . .0.00in
UCAaxleY . . . . . . . . . . . . . .0.00in
UCAaxleZ . . . . . . . . . . . . .20.63in


CALCULATED
LCAlength . . . . . . . . . . . . . . .18.440in
LCAplanviewlength . . . . . . 18.436in
LCAsideviewlength . . . . . . 18.379in

ANTISQUAT . . . . . . . . . . . . .31.53%



Norm
 
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BMR Tech

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Here is a quick comparison, showing how crucial the rear IC/AS settings are.

The car in this video is a Brembo 2013 GT on stock tires w/35psi.

The first video is all stock geometry, with BMR UCA/UCM and BMR LCA:
http://www.youtube.com/watch?feature=player_embedded&v=-oqn-wQrPU4

As you can see, wheel-hop is still there. I suggested that he drop the UCA down to the lower mounting position on our bracket.

The only change was lowering the UCA Mounting point 1", which shortened the IC and raised the AS%.
http://www.youtube.com/watch?feature=player_embedded&v=LD12TIjKmow

As you can see, wheel-hop was completely eliminated.(traction was increased substantially) :beer:
 

luv2cheat

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Here is a quick comparison, showing how crucial the rear IC/AS settings are.

The car in this video is a Brembo 2013 GT on stock tires w/35psi.

The first video is all stock geometry, with BMR UCA/UCM and BMR LCA:
http://www.youtube.com/watch?feature=player_embedded&v=-oqn-wQrPU4

As you can see, wheel-hop is still there. I suggested that he drop the UCA down to the lower mounting position on our bracket.

The only change was lowering the UCA Mounting point 1", which shortened the IC and raised the AS%.
http://www.youtube.com/watch?feature=player_embedded&v=LD12TIjKmow

As you can see, wheel-hop was completely eliminated.(traction was increased substantially) :beer:

So in moving the upper arm down did it take bite (or hit) out of the car? It seems to me that it would have less A/S by looking at one of the diagrams you posted earlier.

I just want to be sure I have a good understanding of this.
 

fdjizm

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Here is a quick comparison, showing how crucial the rear IC/AS settings are.

The car in this video is a Brembo 2013 GT on stock tires w/35psi.

The first video is all stock geometry, with BMR UCA/UCM and BMR LCA:
http://www.youtube.com/watch?feature=player_embedded&v=-oqn-wQrPU4

As you can see, wheel-hop is still there. I suggested that he drop the UCA down to the lower mounting position on our bracket.

The only change was lowering the UCA Mounting point 1", which shortened the IC and raised the AS%.
http://www.youtube.com/watch?feature=player_embedded&v=LD12TIjKmow

As you can see, wheel-hop was completely eliminated.(traction was increased substantially) :beer:

How much percentage is moving it to the lower hole?
I have the BMR UCA bracket with the arm in the lower hole since installation, because racecar of course. I don't plan on moving it lol

those are awesome vids!
 
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luv2cheat

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This may not be the right place to ask this question but here goes. Whats best, lowering the upper arm front hole (using a multi hole mount) or lowering the lower arm at the rear (relocation brackets)?
 

fdjizm

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I don't see why you would ever lower the front mounting hole.
I'd say stick with lowering the rear via brackets.
 

fdjizm

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My bad I read that wrong!!! I thought you were talking about the LCA's for some reason.
My UCA is also on the lower mount of the BMR bracket. Not sure which setting has more of an effect.
My LCA's are in the top bracket of the relocation brackets, might try the middle for track days.
 

psfracer

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So in the videos above, was the LCAs still at the stock geometry? I.E. parallel to the ground, and just the UCA was moved to the lower hole?

Great videos.
 

BMR Tech

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Correct. The car was stock ride-height, all stock geometry.

When an S197 is lowered, I usually recommend AGAINST using the lower hole on the UCA....instead, I urge using the LCA Relocation Brackets to set IC/AS.

The reason is because, when you lower the car....you are dropping the front of the UCA down already, so when you "fix" the LCA with Relocation brackets, AND drop the UCA position down....you start running into issues of having too short IC, and too much AS.
 

psfracer

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Ok, so on a smaller tire a couple months ago this is what was happening:

The car would hook great the first 20-30 feet, then it would break loose. I went back to a 10.5W and all is fixed.

So generally, what is happening if a car hooks hard first, but then spins 20-30 feet out? To much anti-squat?
 

psfracer

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So to correct too much anti-squat, where does the IC have to move to? Further out and down?
 

BMR Tech

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That is where it get's complicated.

In simple words, the AS% has to drop.....meaning IC (point where the control arms meet) needs to typically move further forward, or down, but it just depends.

AntiSquat.jpg
 

wbt

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psfracer - what I did was move my UCA to the top hole and kept the LCA relo brackets on the car. This reduced the AS by ~30% and placed the IC very close to the CoG.

I am using full CHE brackets and control arms. The LCA relo bracket mounting holes are the same location as the middle hole on most of the 3 hole LCA relo brackets.
 

BMR Tech

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psfracer - what I did was move my UCA to the top hole and kept the LCA relo brackets on the car. This reduced the AS by ~30% and placed the IC very close to the CoG.

I am using full CHE brackets and control arms. The LCA relo bracket mounting holes are the same location as the middle hole on most of the 3 hole LCA relo brackets.

What is the measurement from the stock location, to the position in those brackets? 2.5", 3.0", 3.5"? That would be good info to share sir.:beer:
 

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