ladies_first

ok , so i looked through a couple of threads and i have a couple questions regarding some terms i didnt quite understand fully...
THIS IS MY RESEARCH , but bc my experience level is at a 10 right now im completely clueless to what some terms mean

i have 95 eg coupe and i wanna change the suspension all around. i dont want to just lower my car.

what does "BODY ROLL" mean ? im going to guess that it has to do something with turning and not have the car completely flip. but like i said, im not a professional , so correct me if Im wrong.

"If you want all the body roll virtually gone, go with a big front/rear set up that compliments your spring rates"
i got that from another thread , can anyone explain that to me ?

Another thing that sounds like its important to include,
i have H&R struts. i havent put them on yet but thats not the only thing i wanna do. i wanna "improve" basically the suspension/chassis itself.
idk how good these are, brand wise. i bought them a while ago very cheap so i threw myself at them hehee ....

i just thought id start my own thread so i can get personal responses rather than just go from thread to thread guessing on whats right and wrong.

anyway, any information would be REALLY helpful on making my decision on what brands, improvements, etc. to make.
thank you for your time (:

ej6fade

"On wheeled or tracked vehicles, body roll is a reference to the load transfer of a vehicle towards the outside of a turn. When a vehicle is fitted with a suspension package, it works to keep the wheels or tracks in contact with the road, providing grip for the driver of vehicle to control its direction. This suspension is compliant to some degree, allowing the vehicle body, which sits upon the suspension, to lean in the direction of the perceived centrifugal force acting upon the car. Anti-roll bars are a part of the suspension specifically designed to address body roll.

When a vehicle is fitted with a suspension there is compliance between the mass of the vehicle and the vehicle's contact with the ground. Body roll is the noticeable (either perceived or measurable) deflection produced when load transfer acts on the compliant elements of the suspension. Anti-roll bars directly impact body roll but their design intent is actually as a tool to adjust roll couple percentage or roll moment distribution."

http://en.wikipedia.org/wiki/Body_roll
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"Stabilizer bars are part of a car's suspension system. They are sometimes also called anti-sway bars or anti-roll bars. Their purpose in life is to try to keep the car's body from "rolling" in a sharp turn.

Think about what happens to a car in a sharp turn. If you are inside the car, you know that your body gets pulled toward the outside of the turn. The same thing is happening to all the parts of the car. So the part of the car on the outside of the turn gets pushed down toward the road and the part of the car on the inside of the turn rises up. In other words, the body of the car "rolls" 10 or 20 or 30 degrees toward the outside of the turn. If you take a turn fast enough, the tires on the inside of the turn actually rise off the road and the car flips over.

Roll is bad. It tends to put more weight on the outside tires and less weigh on the inside tires, reducing traction. It also messes up steering. What you would like is for the body of the car to remain flat through a turn so that the weight stays distributed evenly on all four tires"

http://auto.howstuffworks.com/question432.htm

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"Anti-roll Bars

The primary function of anti-roll bars is to reduce body roll by adding to the roll resistance of the springs.

An anti-roll bar, also referred to as a stabilizer or sway bar, is a bar or tube which connects some part of the left and right sides of the suspension system. On independent suspension systems, the connection point is usually the lower control arm.

Most cars have a front anti-roll bar, and most sports cars are going to have both a front and rear bar. After market bars are going to be stiffer than the stock ones.

Roll Resistance

Anti-roll bars are used to reduce body roll during cornering. They add to the roll resistance of the suspension springs for a higher overall roll resistance Because the primary purpose of the spring is to maintain maximum contact with the road surface over imperfections, we must settle for the roll resistance provided, and it is rarely enough. The anti-roll bar adds to the roll resistance without resorting to an overly stiff spring. A properly selected anti-roll bar will reduce body roll in corners for improved cornering traction, but will not increase the harshness of the ride, or reduce the effectiveness of the tire to maintain good road surface contact.

So, how does limiting body roll improve handling? The suspension system geometry (the lengths and connecting points of its parts) of a street car is designed to keep the bottom of the tire parallel with the road for maximum contact patch. At rest, the car's suspension has a particular geometric relationship to the road surface. Body roll changes that relationship, and reduces the suspension's ability to keep the tire parallel to the road.

During body roll, the car body is no longer parallel with the road, and neither is the suspension geometry. Even though the suspension allows the wheel to be somewhat independent from the body, the high cornering forces, and resulting large body roll of a factory car, on the track take the suspension close to its limits where it affects the angle of the wheel.

Large amounts of body roll cause the wheels to tilt away from the corner which lifts the edges of the tire and reduces the contact patch size. While this can be compensated for by having the wheel purposely tilted inward to start (adding negative camber), there is a practical limit to this which is not enough in most cars to compensate entirely for the body roll. The anti-roll bar reduces the amount of body roll, and therefore helps to maintain as much of the contact patch as possible.

As with all good things, more is better only to a point. Because the anti-roll bar connects the left and right sides, this reduces the independence of independent suspension. Too stiff a bar, and you can cause too much loss in the ability of the left or the right wheel to independently respond to road surface imperfections. The purpose of suspension is to maintain maximum tire contact with the road. The purpose of independent suspension is to allow the left and right wheels to each seek that contact separately. The left wheel may need to be going down when the right needs to be going up. If they were tied together as with the old floating rear axles, one or both of the wheels is not achieving maximum contact. In fact, too stiff an anti-roll bar can actually cause an inside wheel to lift completely off the ground during hard cornering.

When cornering, the bar will twist with the outside end being pushed down, and the inside end being lifted (just like the body of the car). On the outside tire, this downward pressure helps increase tire traction. However, on the inside tire, the anti-roll bar is pushing up on the suspension reducing the downward force the spring is trying to place to keep the tire on road. If the anti-roll bar is too stiff, it will overpower the spring, prevent it from extending enough to keep the tire on the road, and the wheel will actually lift off the ground. This is not an optimum situation, but it is common in several racing classes. The cause is not so much poor engineering, but the limitations of the class rules that allow the engineer to compensate for it.

Roll Coupling

The anti-roll bar is also used to tune the roll coupling of the chassis. Roll coupling is the relationship of the roll resistance of the front of the car and the roll resistance of the rear.

The balance of the roll coupling, because of its effect on traction, has influence on whether the car has a tendency to understeer or oversteer. While this can be caused by several factors, the anti-roll bar (especially, an adjustable one), can be used to compensate.

As we mentioned, the anti-roll bar helps increase the mechanical downforce of the outside tire during cornering. This increases the traction of that tire, and that end of the car (front or rear). An increase in traction at that end, may leave the opposite end with too little traction. An imbalance of traction occurs, and one end of the car will lose traction before the other end. If the front tires lose traction before the rear tires, the car will understeer. If the rear tires lose traction before the front tires, the car will oversteer. Changing the anti-roll bar stiffness can adjust this out.

Summary

The anti-roll bar reduces body roll to keep the suspension geometry, and ultimately the tire, parallel with the road. Stiffer bars reduce body roll more, but too stiff a bar can deteriorate independent suspension performance, and ultimately cause an inside tire to lift off the ground during hard cornering.

The anti-roll bar can also be a major tuning element in reducing excessive understeer or oversteer. Used incorrectly it can also cause it.

Like other parts you can buy for the car, the "killer" biggest, stiffest anti-roll bar you can buy is rarely going to be the appropriate choice. Look for someone experienced with your car, and can take into account the shocks and springs already installed in your car."

http://www.turnfast.com/tech_handling/handling_antiroll

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Dealing With Body Roll


Body Roll Factors

Center of Gravity & Roll Center There are several basic terms that need to be explained in order to understand what affects body roll. They are center of gravity and roll center.
Center of Gravity: The center of gravity (CG) is that point that all the masses in the vehicle can be considered to be concentrated.

Roll Center: The roll center (RC) is a point where the car pivots. There is one in front and in one in the back and the car pivots about a line (roll axis) between the two roll centers. When the car is in a corner, it will lean (roll) about the roll axis.

The most dramatic impact to body roll is center of gravity height. This is affected by the CG distance from the roll center height. The greater the distance between them the more body roll. Consider the example below. This simplified vehicle has a high center of gravity and is offset considerably from the roll centers and roll axis. When a cornering force is applied the body will lean. You can see that if the CG was closer to the roll axis, in the same corner the body lean would be reduced.

Why is This Important?

From this discussion you would think that just lowering the vehicle by using shorter springs would result in an improvement to handling. While it is true that you will lower the CG by lowering the car, you can also adversely impact the roll center, steering geometry or both. Even if the ride height is not changed the roll center can be a problem that needs to be understood

We are only going to address the front roll center because it is the easiest to change and will provide the most amount of improvement. The RC of a symmetrical, independent suspension is determined by utilizing a front view of the suspension pivot points and drawing imaginary lines to connect the ball joint, point B and inner pivot, point A of each control arm and extending them to the point where they intersect, point C. This point is called the instant center and is the point at which the wheel (if attached with a single bar) will move about in an arc.


Drawing another line from the centerline of the bottom of the tire, point E to the instant center, point C and still another set for the other side of the suspension will give you the roll center. It is the point where these two lines meet. The height of the roll center is measured from ground level.










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took all of 60 seconds. You know when you take a turn hard and you feel the car tipping, or leaning, to one side or the other? like when you make a hard left, your body and your car lean right? that is body roll.



"If you want all the body roll virtually gone, go with a big front/rear set up that compliments your spring rates"

if you are asking what that means, you need to develop a much better understanding of how suspension works and how all the parts affect each other. I hope you aren't expecting to be spoon-fed information, because you will quickly realize that this not how H-T works.

then what do you want to do? are you just daily driving it? track? auto-x? daily and weekend warrior? drag racing? lacking a lot of details here. What is your budget like?? Full coilovers or shocks/coilovers or shocks/springs?

I understand everyone starts somewhere, but we are not going to spoon feed you. Being a noob is no excuse, before I even looked into brands and parts I spent two months developing a full understanding of how suspensions work, suspension geometry, types of suspensions, vehicle dynamics, etc.
I started on here, read the stickys, and here: http://www.carbibles.com/suspension_bible.html

Google is your friend.