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Fuelie600

Active Member
Joined
May 25, 2001
Messages
1,847
What are your opinions on altering "instant center" on these cars? My GN is a low 10's car, and I will be running HR&Parts bar, Metco fixed lowers, and Metco adj. uppers. This is also a street driven car. Thanks, Brian
 
Brian, are you running a T-brake? What stall is the converter?
IMO, the IC should be located properly for best results. However, the results will be much better if you are shocking the tires with a t-brake and/or a good stall converter. When I altered mine I could feel the difference but b/c I power brake the car to 15psi this preloads the suspension so much the geometry doesn't have a chance to "work". But when you shock the suspension with a t-brake then things work much beter..

ks:cool:
 
Brian, are you running a T-brake? What stall is the converter?
IMO, the IC should be located properly for best results. However, the results will be much better if you are shocking the tires with a t-brake and/or a good stall converter. When I altered mine I could feel the difference but b/c I power brake the car to 15psi this preloads the suspension so much the geometry doesn't have a chance to "work". But when you shock the suspension with a t-brake then things work much beter..

ks:cool:

I'm running a TH400 w/brake. Convertor is a ATI fuel/blown. These were just installed, so I have no track time with them ( it's 0* outside ). The reason I posted this thread was because my Metco lowers came w/ brackets to lower the rear mounting point of the lower control arms to alter IC. Some say not to install these, and to stick with fact mounting points, and to just adjust the pinion angle with the uppers. This IC stuff his is a bit new to me, and I'm trying to inhale it as fast as possible. Lowering the fronts of the uppers makes sense, but I'm confused as to where I need to place the intersect point ( IC ). I also run slicks. Brian
 
Leave off the AS brackets and bolt them to the factory holes. Do you have enough tire clearance that you can lower the rear of the car so the LCA is horizontal with the ground? If so I would do this which moves the IC back and lower which is better. You can always try it with/without the brackets to see how it works..

ks
 
Does anyone make brackets to lower the front of the upper control arms? Thanks, Brian
 
Does anyone make brackets to lower the front of the upper control arms? Thanks, Brian

Not that I know of but all you need to do is weld some flat plates to the torque boxes and drill some holes.

ks
 
I'm running a Moser 10 bolt housing. The upper control arm mountings are much beefier and the location has been moved up. This moves the IC back and down and helps plant the tires when the suspension is shocked. It also controls the cars tendancy to wheelie. Traction has not been a problem with 10.5" slicks. Maybe it's helping.
 
I'm running a Moser 10 bolt housing. The upper control arm mountings are much beefier and the location has been moved up. This moves the IC back and down and helps plant the tires when the suspension is shocked. It also controls the cars tendancy to wheelie. Traction has not been a problem with 10.5" slicks. Maybe it's helping.

Don, Any idea how much the mounting point was moved?
 
IMHO, if you have the adjustable UCA's, you may as well set the IC.
I am FAR from any expert, but, did you see this thread?
http://www.turbobuick.com/forums/general-turbo-buick-tech/60687-lower-control-arms.html

If you are referring to the adjustable uppers as a way to move the instant center.... no good.... it can't move it. the angle of the bar is still the same.... you would change the pinion angle... yes..... but not the instant center. You have to change tha angle of the bar.... usually by moving one end up or down..that moves the instant center....

Lakewood makes some "no-hop" bars that alter the IC. Also...someone made some ears you could weld on to the LCA brackets on the rear end to lower the LCA's a couple of inches... that will move it.
 
If you are referring to the adjustable uppers as a way to move the instant center.... no good.... it can't move it. the angle of the bar is still the same.... you would change the pinion angle... yes..... but not the instant center. You have to change tha angle of the bar.... usually by moving one end up or down..that moves the instant center....

Lakewood makes some "no-hop" bars that alter the IC. Also...someone made some ears you could weld on to the LCA brackets on the rear end to lower the LCA's a couple of inches... that will move it.

My Metco's came with the brackets you are refering to.
 
If you are referring to the adjustable uppers as a way to move the instant center.... no good.... it can't move it. the angle of the bar is still the same.... you would change the pinion angle... yes..... but not the instant center. You have to change tha angle of the bar.... usually by moving one end up or down..that moves the instant center....

Lakewood makes some "no-hop" bars that alter the IC. Also...someone made some ears you could weld on to the LCA brackets on the rear end to lower the LCA's a couple of inches... that will move it.

You are correct.
I had the PA and IC confused.
 
I have the Metco lowers and I used the brackets to lower the rear of the control arm but in my case the car itself had been lowered which messed with the IC...before I did anything the LCA's were parallel to the ground and maybe a little higher in the rear...after the Metco/bracket install the LCA's are now just a little lower in the rear compared to parallel...I think that's the right way to go to move the IC back...from what I've read lowering the rear of the LCA helps move the IC back towards the rear of the car which in turn helps plant the tires better...I'm by far no expert on this...this suspension stuff still confuses me...
 
The upper control arm mounting point on the 12 bolt Moser housing is cast 1.00" higher than the OEM mounting point. I called and checked with Moser and 1.00" is the exact dimension. This pulls the IC back. Where it puts it exactly? I've never calculated that out. Maybe some of guys with the sims can let us know.
 
Well..... plotted out on AutoCAD.... using my initial measurements as "stock".... raising the rear UCA's up 1" at the rear mounting point....has a tremendous effect on the instant center. It moves it down almost 3" over stock.... and back about 63" over stock. This (assuming my initial measurements on my car were accurate) makes the instant center about 66" in front of the rear axle....about 11-1/2" off the ground.

So stock IC lies in front of front tires by 22" or so.... the new one is 41" behind front tires.

Take that for what it is worth.
 
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