Malibu Instant Center calculations

TNTS79

Dragway Regular
Jan 6, 2006
1,252
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Illiniois
Here are some quick figures from my car, used baseline suspensions calculator. Rearend is a 12 bolt GM, aftermarket HPM upper control arms for a 12 bolt and tubular double adjustables from Iceman. Let me know if any of the figures seem out of line and I can remeasure them. Just wondering what some of you have done to adjust control arm mounting locations to alter instant center / antisquat values on your rides. Mine pretty much pops the tires straight up, seems to be pulling the tires out of the beam which is giving me fits launching consistently...
I inverted the values for the lower control arms front to rear, duh...

Current Values (car still squats a little) Will double check measurements and update accordingly.


If I lower the rear lower control arm mount 1"



If I lower the front upper control arm mount 1/2"

 

TNTS79

Dragway Regular
Thread starter
Jan 6, 2006
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Illiniois
I would be happy with it leaving with the front end on the ground if it would be more consistent rather than using energy launching the front end straight up in the air...

 

mean78malibu

Dragway Regular
Mar 15, 2008
998
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16
Pittsburgh, PA and Philly Area
I would try option 2 first. Moving both upper and lowers puts your IC pretty far behind the CG.

Your plot with the 12 bolt looks a lot better than mine the GN 10 bolt. Maybe because you aren't lowered as much as I am.
 

TNTS79

Dragway Regular
Thread starter
Jan 6, 2006
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Illiniois
Moving the lower control arm down 1" should hit the tires a little harder than moving the upper control arms but...

There is a nice set of buckets and control arms from Baseline suspensions for $320 that would allow the upper control arms to be repositioned - would be a nicer setup than moving my lower control arms... Anyone installed one before? Guess I could buy just the buckets as I already have useable offset upper control arms for the 12 bolt.

 

TNTS79

Dragway Regular
Thread starter
Jan 6, 2006
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Illiniois
If I move the upper control arm mount down 1" it calculates out to 152.75 AS
 

10secBu

MalibuRacing Junkie
May 21, 2003
4,284
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36
Westminster, MD
What tire, slick or radial?

How much power?

Myself I like #3 the best out of the 3 you have shown. On a radial I would go shorter.
 

TNTS79

Dragway Regular
Thread starter
Jan 6, 2006
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Illiniois
Tire is MT ET drag now. Best 60 ft on the slicks is a 1.48. Back when I ran the pro series 275 radial it 60ft a best of 1.45. Power estimate around 450 hp at the tires. 3400 lb car 6.92 @ 97 fastest it has been on the radials
 

Ed Cannon

Pro Stocker
Jul 17, 2009
1,682
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Johnson City Tn
I've always been interested in this stuff. I know what instant center is, but don't know where the optimum position is and what effects the wrong position has on the car.
 

10secBu

MalibuRacing Junkie
May 21, 2003
4,284
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Westminster, MD
I will say on drag radials with my 1200 hp N/A bbc I run the IC at 35" long and just shy of 10" high. I believe the A/S is 150%.

I'll be reconfiguring the bars for slicks here in the next couple weeks and will be shooting for 45-48" long and 7" high or so, A/S close to 100%.

Radials need a hard hit to plant the tire. Slicks can't handle that hard of a hit (without balling the sidewall up) so they need a longer and lower IC.
 

TNTS79

Dragway Regular
Thread starter
Jan 6, 2006
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Illiniois
I am just starting to get a little of an understanding. If the intersection point of the control arms is infront of the center of gravity it will cause the nose of the car to lift more potentially resulting in a wheelie contest ride type of setup... Still a little unclear as to what role the instant center length and height play??

Higher anti squat % = hitting the tires harder and increased chassis separation which is a good thing given the power level in my car. Would a shorter instant center length and lower height be better or vice versa...??

I would prefer for my car to turn a faster 60ft by using the power it's making to push the car forward not upward. I'm just hoping some of the guys chime in with changes they have made / results...

Currently I am leaning towards the baseline suspension kit. If I tie the upper control arm braces to the frame and weld in the baseline mounting boxes mine should be pretty stout and adjustable if I change the car in the future.
 

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