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Where is the instant center?

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Blazer406

Mechanical Engineer
Joined
May 2, 2002
Messages
5,068
Hey guys.... about to plot out the rear suspension geometry on AutoCAD and want to play with the Cg and instant center. I really want to analyze what is stock..... and see if I can determine how much the instant center needs to move. I plan on making the necessary measurements... just wanted to see if anyone else on the board went to the trouble... and what did they find? This suspension book I bought called "Doorslammers" is very informative. Anybody else like this book?
 
http://www.baselinesuspensions.com

He knows how to do it. He is a member here, username KEVINS. He helped me.

FWIW, my instant center is basically in the center of the car and perpendicular to the crack of my azz, no kidding.
 
John said:
FWIW, my instant center is basically in the center of the car and perpendicular to the crack of my azz, no kidding.

Now that is funny right there... I don't care who you are!

I'll try and take my measurements tonight and report back...... It will vary from car to car with different ride heights. It will be a snap to plot out in AutoCAD once I have the heights of all the control arm mounting points and the length of the control arms.......
 
My measurments are as follows:

RLCA rear point = 8-7/16" off ground
RLCA front point = 9-3/8" off ground
RLCA = 20" long

RUCA rear point = 17-3/8"
RUCA front point = 17-1/8"
RUCA length = 11-1/8"

Autocad says intersecting point is 10'-8 15/16" ahead of rear axle centerline which falls about 22" in front of front axle centerline

This point was 14 7/16" off the ground.

Now I have to read up in my doorslamers book and see what that tells me....
 
Blazer406 said:
My measurments are as follows:

RLCA rear point = 8-7/16" off ground
RLCA front point = 9-3/8" off ground
RLCA = 20" long

RUCA rear point = 17-3/8"
RUCA front point = 17-1/8"
RUCA length = 11-1/8"
....

Does your car have bone stock suspension? How old are the suspension pieces?

Keep us posted....I'm tryin to design a 3-link for a 9" under my GN.
 
FBSideoiler427 said:
Does your car have bone stock suspension? How old are the suspension pieces?

Keep us posted....I'm tryin to design a 3-link for a 9" under my GN.

Yes, currently my suspension is stock. I have a HR Parts anti roll bar and some of their control arm bushings I am installing in the next few days. I have also not checked for the missing factory body bushings yet..... not sure which ones are the ones that are commonly left off.... all the ones toward the back are there. I am running 4 GTA front wheels with 245/50/16 tires. The measurements are the best I could do with a tape measure... trying to slide under the car w/o jacking it up. I probably should try to remeasure with a string and a plumb bob...to get a little more accurate.... I feel they are real close... it is just difficult to do w/o some help or having the car jacked up.... but that would interject more variables.....
 
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