instant center?

from what i understand instant center is the point where upper and lower 4 link bars would intersect if they were extended past the front pivot points going towards the front of the truck..what is the optimum location for instant center? what does placing it properly do for you? and what if the bars are parallel? is there no instant center?

http://www.streetsource.com/forum/Topic.aspx?topic_id=88500&forum_id=16&Topic_Title=instant+center+and+pinion+angle+for+BioMax&forum_title=Suspensions

http://www.streetsource.com/forum/Topic.aspx?topic_id=85853&forum_id=16&Topic_Title=BioMax

If you really want to get down and dirty and measure it all out, I'll try and explain it the best that I can...
Looking at the diagram that Terry posted, you would first want to find your over-all length (which you have- 144") then you would find the distance that the tabs on the rearend are apart (you have that too- 9 7/8") then you need to decide how long your bars are going to be (that's fairly easy let's use 36" to keep things simple) With these numbers you can calculate the disatnce that your front tabs should be apart.
9.875(rear tab distance) / 144(overall length) = .069(tab ic ratio)
144(overall length) - 36 (bar length) = 108(let's call this the secondary bar length)
108(secondary bar lengt) x .069(tab ic ratio) = 7.45(front tab distance)
Hopefully that all made sence...
From here you would need to make sure that your bars are near parallel to the ground a half travel to keep rollsteer in check.
As for your pinion angle, it sounds to me that your half travel angle should be 0.

There from the man himself

To anser your other question if your bars never intersect and are parallel to each other then the IC is infinate.

Originally posted by Gangsta Boogie



what is the optimum location for instant center? what does placing it properly do for you? and what if the bars are parallel?



The optimum location for the ic depends on what you what the suspension to excell at. Most of you are just looking for a good overall driving vehicle, so the best placement would be around the bumper(ish.) There is no exacly proper location though, the ic is constantly moving around anyhow so that is why I say bumper(ish.)

If you run the bars parallel then the dynamic energy that is being transfered to the chassis will be wasted doing nothing. Having an ic. gives the energy someplace to go and aids with traction and braking.

You got a full time job in this department max lol

It seems that way some times, but as long as you guys are willing to listen, I'll keep typing...

What did you say? lol hell yeah ill take your advice anyday.

max i have learned so much from just iming you, reading your articles, and your most on forums.....keep it up we all are gratefull even though most people wont admit it.

basically the advantage to properly placing the instant center would increase traction during acceleration and decelration? when the vehicle is at a constant speed does a suspension with no instant center perform any different than a suspension with an instant center at the front of the truck?