Suspension 101: Components of Suspension & What They Do [sticky?]

[The Mic]

All info taken an posted here are courtesy the links listed below by Chingon.....

Suspension 101:Components of Suspension & What They Do

Introduction

Handling of a vehicle is determined by many variables. Some ofthese are tires, center of mass (a.k.a. center of gravity), chassistorsional stiffness, suspension geometry, suspension components(springs, shocks, anti-roll bars), etc.

There are many things that most people do not wish to change due tovarious reasons. For example, most people do not want to strip theinterior of the car to lower the center of mass. It isunderstandable as it would make a very impractical street car.Installing roll cage is not a really good idea for a street car,either. Changing the suspension geometry is not recommended withoutthorough understanding of the vehicle dynamics. Changing suspensioncomponents is the easiest way to alter the handling characteristicsof the vehicle.

Tires

Tires are black rubber things that provides the only contact withthe road surface. Friction between tires and the road surfacecreates acceleration, braking (deceleration), and cornering. Mostof you learned in high school physics that:

Ff = Cf * Fn

where Ff is the friction, Cf is the coefficient of friction, and Fnis the normal force. Well, ladies and gentlemen, I got news foryou. This equation only applies to very special cases where bothsurfaces are very hard and have reasonably smooth finish. Thisequation certainly does not apply for tires.

Tire's frictional property can not be expressed as an equationreally well. If I use the above equation, Cf will decrease withincrease in Fn. As normal force increases, coefficient of frictiondecreases. As a results, friction force does not increase as muchas increase in normal force. An important result of this, is thatlighter cars will turn sharper corners than heavy cars, all elsebeing equal.

Weight Transfer

Weight transfer is a shifting of loading on tires due toacceleration. Increasing speed, braking, and cornering cause weighttransfer. For transverse acceleration, weight transfer can beexpressed as:

dW = (m * h * a) / t

where dW is the resulting weight transfer due to acceleration a (inm/s^2 for metric unit and G in U.S. unit when lb. Used for mass),m is the mass of the vehicle (kg for metric unit and lb. for U.S.unit), h is the height of center of mass, and t is the track width.For longitudinal weight transfer, use wheel base instead of t.

This equation calculates the total weight transfer but does notcalculate how much weight is transferred by front or rear wheels.It required more complicated equation and a lot more details andassumptions to calculate the weight transfer by each wheel, and Iam not about to get into that.

Just remember that, if you make on end of the car stiffer, therewill be more weight transfer at that end and lose some tractioncapability due to increase loading on that end.

Springs

Springs are energy storing device. They store energy by deflection.Most springs are constant rate springs, i.e., amount of the forcethat is stored is proportional to the deflection of the spring. Itis usually expressed as:

F = k * X

Where F is the force (in lb., at least in the U.S.), k is thespring constant (or spring rate) in force per deflection(lb./inch), X is the deflection (in).

There are also progressive springs. Progressive spring's springconstant (k) increases with deflection.

OK, enough about what springs are. We can now talk what springs doin a car. Springs absorb bumps, limits the motion of the vehicledue to acceleration, braking, cornering, etc.

Shocks

Shock absorbers dampen the motion of suspension. Shock absorbers donot absorb impacts; springs do. Shock absorbers are dampers.

Shock absorbers also control the transient motion of the vehicle.Shock absorbers control HOW the car nose dive when brake isapplied. Springs control HOW MUCH car nose dives. Shock absorbercontrols HOW the car goes into roll when the steering is applied.Springs and anti-roll bar control HOW MUCH car rolls.

There are some adjustable shocks available. Adjusting the extensionof the shock is called "rebound," and adjusting other direction is"bump."

Anti-Roll Bars

Anti-roll bars are also known as roll bars, sway bars, anti-swaybars, etc. Anti-roll bars connect right and left wheel. They resistroll by twisting themselves, acting as torsion springs.

Tuning Springs, Shocks, & Anti-Roll Bars

You have to understand few terms before I can explain how to tunesuspension.

Understeer ("Push" for circle track people): Handlingcharacteristic that, when car is turning on the constant radiuscircle, front end of the car pushes to the outside of the circlewith increasing speed. Turning radius of the car increases withincreasing speed, or more steering is necessary with increasingspeed. It is caused by front end of the car having less tractionthan rear end.

Oversteer ("Loose"): Handling characteristic that, when car isturning on the constant radius circle, rear end of the car pushesto the outside of the circle with increasing speed. Turning radiusof the car decreases with increasing speed, or less steering isnecessary with increasing speed. It is caused by front end of thecar having more traction by rear end.

Neutral: Ideal condition that is rarely achieved. Car turns on theconstant radius circle with constant steering angle with increasingspeed. As strange as it seems, some racing cars can do this, untilyou lose traction and get into severe oversteer.

Entry: Imagine that you are approaching a long sweeper. Turn-in iswhen you turn the steering and wait for the car to "settle" tosteady state roll angle.

Steady State: Your car is finished turning in. You are giving thecar constant steering angle and throttle angle.

Corner Exit: You are beginning to get on the gas pedal and unwindsteering.

Symptoms & Solutions

Entry Understeer: Increase the rebound of rear shocks. Decrease thebump of front shocks. Increase the rear brake bias. Brake earlier.

Entry Oversteer: Decrease the rebound of rear shocks. Increase thebump of front shocks. Decrease the rear brake bias.

Steady State Understeer: Stiffen rear spring and/or anti-roll bar.Soften the front springs and/or anti-roll bar.

Steady State Oversteer: Stiffen front spring and/or anti-roll bar.Soften the rear springs and/or anti-roll bar.

Exit Understeer: Increase rebound of front shocks. Decrease bump ofrear shocks. Stiffen rear springs/anti-roll bar. Soften frontsprings/anti-roll bar.

Exit Oversteer: Decrease rebound of front shocks. Increase bump ofrear shocks. Soften rear springs/anti-roll bar. Stiffen frontsprings/anti-roll bar.

Car is slow to respond to driver's input: Stiffen the car bysprings, anti-rollbars, and shocks. Increase tire inflationpressure.

Car hops over the bump: Soften the car. Decrease tire inflationpressure.

Conclusion

As you can see, changing one thing can alter the all three stagesof the handling. You will have to make a compromise that best suitsto your requirement. There are also more variables such as rideheight of the vehicle, wheel alignment, tires, driving style, grossweight, etc., that can alter the handling of a vehicle.

[Nismo_Freak]

Have you even read our FAQ?

[llamabeta]

Have you even read our FAQ?

Heh, Nismo_Freak is always there for you S13GUY

[Tsukai240]

Have you even read our FAQ?

thats a great faq. it covers everything.

[The Mic]

ah oops!

[skydragoness]

I thought he was being a smarta$$. Actually, i still think he's being one.

[The Mic]

No, I'm not, and it's awfully presumptuous of you to act like you know my motivations.

[nismofly]

well when you are 99.9% of the rest of the time, i dont blame her

[The Mic]

well when you are 99.9% of the rest of the time, i dont blame her

"Pedantic" is the word you're looking for there.
Modified by S13GUY at 9:41 PM 2/2/2005

[nismofly]

ive always thought of that word meaning you had a sort of one track mind, which i dont think you do

maybe her term wasnt the best way to describe it, but what has been brought up is your bringing of attitude to many threads

although you are better since you got out of time-out

[skydragoness]

No, I'm not, and it's awfully presumptuous of you to act like you know my motivations.

Well, seeing how your'se such a stickler for pointing out dumb people on the boards, i'm more than surprised that you missed the 5 stickies in this forum. I mean, that's not like you. So i just assumed you were being a smartypants (since you did it twice)
Modified by skydragoness5 at 12:11 PM 2/3/2005

[The Mic]

Hah, no I really had good intentions as hard as that may be to believe. Have you seen my "How to: Perform a Leak-Down Test" and "Compression Testing vs. Leak Down Testing" write-ups? I do try to contribute once in a while, as laughable as that may sound, it's true. I remember looking at the suspension faqs above, but I remember just seeing links for some reason. Most likely, my senses were impaired at that time of night or day. I forget.

[skydragoness]

Don't worry. ..this never happened

[Chingon]

Hah, no I really had good intentions as hard as that may be to believe. Have you seen my "How to: Perform a Leak-Down Test" and "Compression Testing vs. Leak Down Testing" write-ups? I do try to contribute once in a while, as laughable as that may sound, it's true. I remember looking at the suspension faqs above, but I remember just seeing links for some reason. Most likely, my senses were impaired at that time of night or day. I forget.

How were they YOUR writeups, when you copy pasted from another board/website?

compression testing: http://www.turborides.com/foru...st211

leak-down testing: http://www.lcengineering.com/T...1.htm

suspension 101: http://zhome.com/Care/suspension_101.htm

Now who's using English the wrong way??

[skydragoness]

How were they YOUR writeups, when you copy pasted from another board/website?

compression testing: http://www.turborides.com/foru...st211

leak-down testing: http://www.lcengineering.com/T...1.htm

suspension 101: http://zhome.com/Care/suspension_101.htm

Now who's using English the wrong way??

[skydragoness]

Still, if your'e going to do a write up in your post, you should cite your sources--which you didn't. I.E. "hey exar-kun i have this info i'd like you to sticky (insert info and the link where it's from) .It's anyone guess if you don't, and noone follows your posts enough to know your 'writing style'..geez

[The Mic]

I told you I was impaired, or did I leave that part out?

[The Mic]

One entry found for write-up.Main Entry: write-upPronunciation: 'rIt-"&pFunction: noun1 : a written account; especially : a flattering article2 : a deliberate increase in the book value of an asset (as to reflect the effect of inflation)

*huff*

[nismofly]

oh so that word was spanish?

eh well its just s13guy, he cant harm any latinos

[Dori Dori]

Somebody needs to lock this bish.

[nismofly]

yeah it does

[Exar-Kun]

DOri, and sky..next time this crap degenerates....let me know. Hell I'll give you my cell.

quit pokin me AM.

Oh, for refences sake1. if you use article information and dont at the least reword/rewrite it..please cite the site pulled from (ala the sticky), but thanks for the effort in contribution, I'd never tell someone to not contribute usefull info.

Locked and edited by me, beacuse I am supposed to god rink soon and just don't care.

-Chet