instant center brackets

[FivePointOhh]

can someone explain these things to me? i understand the function. but i guess i cant find an illustration or in depth explanation of how it works. from the looks of it, does it actuate back and forth for your vehicle to find its instant center on launch? or is it a fixed piece? anyone have pictures of them installed? write ups of how they work? again i know what instant center is and what it does, i just wanna know how the brackets work. pictures/write ups would be appreciated.

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[5.0kid]

Its a fixed piece, that is welded to your axle tube. I am actually going to be installing some on my car over the winter when i go to do the suspension.

http://baselinesuspensions.com/info/4_LINK.pdf diagram
The goal in setting up a suspension is to apply just enough force to the tires to keep them from spinning and let the rest of the force push the car forward.
Draw an imaginary line through the lower control arm forward. Now draw an imaginary line through the upper control arm forward until it intersects the lower line. This intersection is called the Instant Center (IC).

Now imagine the Center of Gravity (CG) of your car concentrated at the shifter handle. Where the IC (Instant Center) is located compared to the CG (Center of Gravity) is what determines how the force of the suspension acts on the car to get it moving. If the IC is too high then there will be too much energy wasted pushing the car skyward. If the IC is too low then there won't be enough force applied to the rear tires and the tires will spin. There are also variables if the IC is in front of the CG or behind the CG. Somewhere there is going to be a position (or more than one) that will apply just enough force to the tires to keep them from spinning and the rest of the force will push the car forward.

While the car is sitting still, the tires have 100% traction. During the launch you don't want to change this. Properly adjusting the IC will maintain the existing traction during the initial launch or Tire Shock. The IC starts working during the first .001 second of the launch and continues for the next 30 feet or so. However, after the first .001 seconds the shocks are playing a very important roll in "maintaining" the traction and allowing the IC to apply the desired force to the tires. For the most part, the IC is what is adjusted to get the initial hook and the shocks should be adjusted to maintain the traction throughout the 60'.

The four control arms on a four link type suspension, when adjusted correctly for a particular car, can help launch a car quicker and use less horsepower doing it. Compared to a ladder bar suspension a 4 link suspension has the added benifit of changing the length of the Instant Center to accomodate more or less front end lift without adding any more Anti Squat.
Definitions:
Anti Squat (AS):
This is a term used to describe how much the rear of the car will Rise or Squat during launch. If a chassis has 160% of AS then the rear will rise drastically, planting the tires violently. By comparison if a chassis has 100% AS then the rear of the car will not rise or squat and if a chassis has less than 100% the rear of the car will squat.
~A common problem with high horsepower cars running Too Much AS is that the tires will plant the tires very hard for the first several feet but then start to unload the tires and spin when the chassis starts to settle. If your car does this, then look into the value of the AS. Much too often racers will detune the engine to "calm down" the launch instead of look into the suspension geometry.
~A common problem with high horsepower cars running Too Little AS is that the suspension will cause the rear of the car to squat which tries to unload the tires. Again racers detune the engine to maintain traction instead of looking into the suspension geometry.

Normal/Neutral Line:
1. Draw a line up through the center of your front wheel.
2. Draw a Horizontal line through the CG until it crosses the line drawn through your front wheel and mark this intersection point. The Normal Line (or Neutral Line) is the line drawn from the Rear Tire contact patch through this intersection. Neutral Line

The location of the IC relative to the CG and the Normal Line (or Neutral line) is what determines what the chassis is going to do. One term used to describe the chassis movement for a 4 link suspension is Anti Squat. An IC that is located ABOVE the Normal Line is said to have more than 100% Anti-Squat. An IC located BELOW the Normal Line is said to have less than 100% Anti Squat.

~4-link settings of 100% Anti Squat should accelerate the car w/o any raising or squatting of the rear of the car.
~4-link settings with MORE than 100% Anti Squat will Raise the rear end and hit the tires HARDER.
~4-link settings with LESS than 100% Anti Squat will cause the rear end to Squat and hit the tires SOFTER.

~IC's that are located IN FRONT of the Center of Gravity (CG) will tend to lift the NOSE of the car.
~IC's that are located BEHIND the Center of Gravity (CG) will tend to lift the REAR of the car.

[FivePointOhh]

ok i understand a bit more...but then i dont. from the pdf you attached, if i'm reading correctly...this instant center is located BEHIND the CG, so the rear wants to rise, making the tires want to unload...so there is too little AS...probably less than 100%?

so in that same pictures, lets assume he has adjustable control arms, what if you shortened your lowers and lengthened your uppers and your IC is now closer to your CG, would your AS increase putting it closer to 100%? is this right or am i putting too much thought into this?

[302army187]

I think my brain melted half way through reading the second paragraph.

[FivePointOhh]

^^ LOL

[5.0kid]

honestly idk why hes talking about CG honestly he confuses me on that but heres a link to my sponsor who sells ICB's http://www.bluecollarperformance.com/mic0003.html

[5.0kid]

The installation of these brackets lowers the rear mounting point of the rear lower control arms, modifying the vehicle’s ‘instant center’. The ‘instant center’ of the vehicle is the point at which imaginary lines drawn to extend the vehicle’s upper and lower control arms would meet. The brackets cause this imaginary point to move toward the rear of the vehicle, reducing the tendency of the rear of the vehicle to ‘squat’ during hard acceleration. Power normally absorbed in suspension compression is instead applied to the suspension mounting points, driving the rear tires downward and significantly improving traction.

These brackets are recommended for vehicles used primarily in drag race applications, and are generally not recommended for vehicles used exclusively in street applications or vehicles used for autocrossing or road racing. As anti-squat is increased, anti-dive characteristics will increase and some vehicles may experience instability during hard, high-speed braking. The installation of the ICM brackets is a complex operation and should not be attempted by an inexperienced installer. The bracket positioning requires careful measuring, including pinion angle determination, to assure proper installation.

[FivePointOhh]

what is talkin about with anti-dive? meaning your car will understeer?

[5.0kid]

when you go to brake your car will fall over on the nose more then usuall because the rear end will want to rise more. so your car will react as though it has very soft springs and shocks already. under braking at the top end my air deflector rubs because i have my shocks at 100/0 and 150 spring rate coil overs

[FivePointOhh]

i see, i emailed the guy at blue collar for further clarification of how this bracket is supposed to work. i honestly dont understand how its supposed to make your rear suspension work any differently than adjusting your pinion angle with adj. u/l control arms? besides those brackets only work with their control arms...just sounds like a relocation kit to me.