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Trying to Learn squat....

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Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Nah. Thanks to racer47 for reminding me about that calculator. Link was on my last computer that crashed. Already had the Boss LCA heights for your other thread. Perfect time to plug the data in. Control arms should be reduced for their 'projected' horizontal length, but close enough for me.

http://www.baselinesuspensions.com/instant-center_general.php
I got our clubs corner scales for the weekend, Looks like the Boss is in for some intensive suspension tuning!

Sent from my SM-G900M using Tapatalk
 
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FWIW - there is a difference in the axle housings on S197s in the castings so if you do go with a torque arm make sure that you have clearance - early housings need to be ground down in order to clear the toque arm underneath - just found this out on my Cortex T/A set up.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
This is how the car is right now. Tomorrow I will raise the rear and see how the corner balancing goes. Looks like I really need to raise the cars rear a fair bit, at least a cm if not two. the front of the car has the A arms horizontal to the ground.

upload_2018-2-9_19-20-43.png
 

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racer47

Still winning after 30+ years
392
497
Exp. Type
W2W Racing
Exp. Level
20+ Years
SE WI
I don't think there is anything wrong with it as is. Going up 1 cm (or 1/2") in the back would be fine too. I'm not sure why you would more than that.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
I have to resist the temptation for over tinkering... But the car is almost at zero degrees now, with no rake... Maybe the 1/2 inch would be fine.
 
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I suggest driving / testing the car before you make any other changes. You already raised the axle side of the lower control arm decreasing anti-squat and roll oversteer.
 
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Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Probably wiser to leave it as is. Maybe just wax the car.....

I passed by the dyno we use too see a friend today. Saw a 2011 GT 500 that was with a stock suspension, The LCA was almost horizontal, I doubt that the lca was more then 2 degrees down to the axle.
 

Grant 302

basic and well known psychic
I suggest driving / testing the car before you make any other changes. You already raised the axle side of the lower control arm decreasing anti-squat and roll oversteer.

Might help if you can also test some turns and see how much you can either goose/stab the throttle vs. roll into it. Results might surprise you. I think there's a lot of wisdom in some previous suggestions about learning to drive 'the fast way'.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
That's what I thought about the stock Boss LCA angle...until I took the measurement to the bolt centerlines.

Yes, that explains why back when I installed the P springs, the car handled so oddly..... The original Boss LCA angle was already pointing down slightly (from the axle) to start with, and lowering it an inch more, made it go too far into roll under-steer.

Currently its pointing up 1.6 degrees (Measured) after sorting out the rear ride heights. Bolts were at F. 6.3" and R. 5.7" Calculated angle is 1.9 degrees. This is all using the BMR brackets on the highest setting.

Added benefit is the car is back at 55% front/45% rear. (and I don't have to worry about scraping the exhaust over the speed bumps).

Off too wax the car and take it for a spin and see if I can notice any difference!
 

Grant 302

basic and well known psychic
Yes, that explains why back when I installed the P springs, the car handled so oddly..... The original Boss LCA angle was already pointing down slightly (from the axle) to start with, and lowering it an inch more, made it go too far into roll under-steer.

Agreed. Did the same mod on the GT with P springs on Boss shocks/struts and total grip suffered. Can't say I noticed it in any sense of roll steer conditions, but lateral grip was definitely missing.

Off too wax the car and take it for a spin and see if I can notice any difference!

Looking forward to the results.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
I could not get a feeling on the road, lots of traffic..... the car is very different with the spherical bushings and new UCA.... Feels solid (Yes, I know... I did lots of changes!)

That and I have my track tune loaded without TC so I was a bit leery of pushing too hard on a public road. Will try to find a decent deserted road asap.
 

Grant 302

basic and well known psychic
Took a bit of looking to find this, but in my opinion it supports what I've been saying:

Antisquat Can Provide Added Traction, But Not In The Way We Might Think
HotRod/Circle Track / Bob Bolles said:
It has been assumed over the years that by applying A/S to rear suspensions, more weight is applied to the rear tires by the mechanical effect produced through the third link. This is not true. The mechanical effect of A/S causes a portion of the load transfer associated with acceleration to be applied to the third link instead of the rear springs. This means we exchange some of the transferred load off the rear springs and onto the rearend where the link is attached.
HotRod/Circle Track / Bob Bolles said:
Since this is an equal tradeoff, there is no more load on the rear tires than before.
HotRod/Circle Track / Bob Bolles said:
The statement that for every action (the A/S forces applying a vertical load to the rearend) there is an equal and opposite reaction (the removal of load from the rear springs) means that there cannot be additional load on the rear tires. This is understandable, because where would the added load come from? In the mechanical world, we cannot receive additional load without taking the same amount of load from somewhere else. So we receive the load from the action of the A/S, and it is taken from the rear springs, to ultimately find itself on the rear tires.

And this is what all those diagrams on the internet are missing! :eek:

A brief resumé is below with some of his credentials:
http://www.hotrod.com/contributors/bob-bolles/

--------

Also found this in the search. Forgive me @Norm Peterson, for quoting you 13+ years later form a different forum and discussion, but I thought it was interesting. My emphasis in bold.

Anti-Squat and Autocrossing

sccaforums / Norm Peterson 18 Jan 2005 05:09 AM said:
Thinking only statically and ignoring the dynamic part of this issue misses the point. What anti-squat does do is load the tires more immediately in response to rear wheel drive torque. If you have zero A/S you have to wait for the rear suspension to adopt the new position that is statically consistent with the rearward load transfer (this wait is primarily a function of the rear suspension ride frequency, essentially 1/4 of the period). If you start to lose grip during the time that the rear is in the process of squatting, which is likely, you've given up acceleration potential not only over that 1/4 rear suspension period time but also over whatever additional time you spend backing off the gas waiting for grip to be re-established.

A/S transfers load to the contact patches over the considerably shorter time span associated with the rear tires' own ride frequency (that 1/4 period thing again), so if you're driving right on the limit of available forward traction it helps keep you out of wheelspin as you add throttle.
 

Grant 302

basic and well known psychic
I could not get a feeling on the road, lots of traffic..... the car is very different with the spherical bushings and new UCA.... Feels solid (Yes, I know... I did lots of changes!)

That and I have my track tune loaded without TC so I was a bit leery of pushing too hard on a public road. Will try to find a decent deserted road asap.

Smart. Wouldn't want you to do anything unsafe!
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
The car will still squat with 50% anti squat.
Less than zero antisquat is how you get wheel hop.
That's the force lifting the wheel and then dropping it back down when it loses traction and cycling over and over.

View attachment 3346
For starters, you need to at least fill in what is happening through the UCA. It's not sitting there doing nothing, and if the suspension squats at all the UCA will be developing some vertical force affecting that squat any time that it isn't perfectly horizontal in side view.

Dynamic tire loading needs to be thought of in terms of time, specifically very short increments of time (milliseconds, not whole seconds). Anti-squat, or kinematic effects 'hit' first (almost instantaneously**), followed by shock effects (based on suspension velocity) and spring effects (suspension position). The timing of these three components matters at least some.

**almost instantaneously because things like suspension bushing and tire compliances take time to happen.


Norm
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
What’s actually happening is usually the simplest thing.
When more than one effect is involved, simplest is going to be a little more complex than when there is only one effect.


Anti-squat does not support ANY weight. The spring supports weight. The ARM(s) can essentially borrow it or momentarily add to or subtract from it during acceleration/decel events. They do none of that in static or set speed instances.
Yes.

And right about here is where this discussion needs to be framed in terms of 'load' and 'load transfer'.


Norm
 

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