mountainbiker2

OK racers. What's the deal. Anytime you read a article on suspension setup you are always told that if the front end understeers go to a softer setup on that end. Whether that be softer springs, sway bars or adjust your shocks softer. Same with oversteer. Go softer setup at that end. So, why do we all put on bigger sway bars and stiffer springs? When you add a stiffer bar, spring on one end, does it make more traction on the other end or do we just lose traction on the end we put the stiffer bar, springs on?

I'm sure it's a compromise somewhere in the setup.
This week I will be able to answer my own question. I ordered stiffer springs and shocks last week. For all the money and time You and I have spent answering all my question about shocks and springs in the last week, it sure better be quicker.

Thanks.
Steve

John Shiels

What did you order?

danswofford

Generally, you make the springs and anti-sway bars stiffer on both front and rear to control body roll in corners. Cars that corner flatter keep more weight on the inside tires, less weight on the outside tires, and corner faster, and better with more control and are easier to drive fast.

You change spring rates, sway bar rates or shock rates on the front or rear, individually, to fine turn the handling characteristics, i.e. understeer or oversteer.

Any you've got the general idea right, whatever end of the car that looses traction first has too much spring weight. The high spring weight transfers more weight onto that tire and overloads that corners ability to hold traction.

63Corvette

Usually you don't have a problem with street tires. When you go to race rubber, you have so much traction that the Gee loading causes (even Z06) stock springs to allow the car to corner on the bump stops. That means the car takes a few seconds to take a "set" and then the frame is the (infinite rate) spring. This costs time in transient maneuvers. In the wet, the setup is usually softer because the wet track will not allow the Gee loading. A car that is too stiffly sprung will track fine on a perfectly smooth track, but will have trouble getting the power down on bumpy pavement.

davidfarmer

it's all relative. You stiften the end with grip, soften the end without. Ultimately you want a stiff race car, but things must be kept in balance. Generally, you are making the other end handle better when you stiften one end.

mountainbiker2

I ordered 960 front, 750 rear springs. VB&P.
Koni's 2812 custom valved from ProParts.

I have a assortment of swaybars to fine tune it.

Steve

63Corvette

Assuming that the rules of your sanctioning organization don't preclude it, wouldn't you be better off with coil overs?
Coilovers with T1 bars

mountainbiker2

Maybe, That was the same question I asked last week. Here is the thread.


http://forums.corvetteforum.com/show...58&forum_id=23


http://forums.corvetteforum.com/show...24&forum_id=23






Nobody I know runs coil overs for autocross. I called LG Motorsports and they said all there testing was done on road race tracks. Not autocross. They use T-1 bars and far as I know no one has been successfully using those for autocross. I also do track events, but more serious about autocross and what works for that. My conclusion is that you can make anything work. Just what route you what to do.

Steve

Solofast

[QUOTE=danswofford]Cars that corner flatter keep more weight on the inside tires, less weight on the outside tires, and corner faster, and better with more control and are easier to drive fast. QUOTE]

That is a common misconception, you don't keep more weight on the inside tires with heavier springs in a car with as little roll as a Corvette. The weight transfer is essentially the same, since it is simply a function of the height of the CG and the width of the car. What stiffer springs do is control the amount of suspension travel, and therefore the camber change is controlled and you get higher grip by keeping the tires more upright...

XPC5R

I run coilovers on my car (Ankeny Penske's with hypercoil springs and rate advice from LGM) It won B-Prepared and placed 2nd in A-Prepared on Hoosier DOT rubber against competition on racing slicks at the Solo II nationals last year.

2 years ago we ran in ASP with T1 bars and small 285 front tires too. those can be made to work pretty well too. You are right, it's all in the tuning, coilovers just make it easier to tune.

As for how stiff is too stiff? a lot depends on your tires and wheels, and the surface you are on. Also driving style - a stiff car is fast, but will be less forgiving at the limit sometimes. Tires with so-so steering response like the car to be stiff, and have lots of rebound damping to set the chassis quickly. 'Edgy' tires, or slick surfaces, want a little more compliance in the shocks, springs, and bars to make them easier to control. Same goes for fast courses - softer is ok, slow courses, stiff helps get the chassis responding quicker.

Vetracr

Don't forget about braking when figuring your spring rates. I normally set my cars front spring rate at the softest I can find to minimize brake dive. You don't want the front suspension on the stops at the turn in point. Once the front spring rate is determined I set the rear spring to match. I believe in the soft spring theory for bump compliance. I use my sway bars to control roll in the corner and shock adjustments to control transients. Books have been written on this subject so there is no easy answer for all cases.

Larry

JonLT4CE

[QUOTE=Solofast]Solofast has it exactly right! I might add though that although total weight transfer is the same, the stiffer end wil get more of it.

vette.se

I was asking Lou at LG about spring rates for coilovers and this was his answer:


If you have stock rear shock pickups on the car you have a different effective wheel rate than a modified shock pick up. The other factor is the angle of the shocks. With the stock shock angle in the rear, you have a “digressive rate” since the wheel rate changes with every inch of wheel travel for the worse. The rear shock angle changes so rapidly that you will have to spring it up stiffer to reduce the variance.

I have run so many track sessions testing our shocks that I can confirm that when we run 700 fronts and 600 rear we have a fine handling car, that is capable of running World Challenge lap times. The stock wheel rate in the rear will actually lower your rear spring rate by 55% at one point in the wheel travel then even lower as the car travels further.

If the car has wings, and front splitter, you must raise the springs rates to 850 front, 750 rear. Again, we have tested this time and time again.

MitchAlsup

Correct

Cars that corner flatter (because of high spring and/or anti-roll bar rates) do not keep more weight on the inside tires! Weight transfer happens--it is independent of the spring and anti-roll bar rates--it is based solely on the CoG and the wheelbase (lognitudinal) and track (latteral) and the amount of latteral acceleration. The springs and anti-roll bars determine the "amount" (AKA response) of body movement from a given amount of weight transfer. See Milliken and Milliken, or Race Car Preperation, vanValkenburg

Cars with low body roll generally have more traction on the inside tire because of lower camber changes on the inside tire! not because of a change in weight transfer. Suspensions are designed to keep the heavily loaded outside tire 'more' straight up on the road surface under cornering. This 'optimization' penalizes the inside tire camber change under latteral acceleration.

{Side notes:: A car with its CoG at the road surface does not generate weight transfer under acceleration loads! Similarly, a car with its roll centers 'at' the CoG will not roll even with zero spring rates. The first is physicaly impossible, the second is practically impossible due to large camber effects under braking and acceleration. One could place the roll centers above the CoG and end up with a car that rolls into the turn rather than away from the turn.}

Cars with stiff springs and anit-roll bars traverse the zone from slipping (high grip) to sliding (more moderate grip) and back more easily (giving more control). This comes from less body movements (and thereby, lower camber changes) as the G forces change when one transitions from slipping to sliding and back.

In addition to changing anti-roll bars to find/maintain the desired oversteer/understeer relationship, one can adjust the O/U relatioinship by adjusting the ride heights at the front (seldom) or rear (generally). This is known as the "roll couple distribution". Some cars are very sensitive to this adjustment (Ferraris) and some are only moderately sensitive (Vettes) while some are practically insensitive (solid rear axles). A 5mm increase in the rear ride height of a modern mid-engined Ferrari can change an oversterring pig into an understeering pig.

Also, the O/U relationship can be adjusted by changing the section width ratio of the tires front to rear. O/U relationship can also be fine tuned with air pressure adjustments.

Whatever end looses traction first may too much spring rate (not weight) but it could also have too much camber change (from too little spring rate)! or it could have too little or too much air pressure.

And as we indicated earlier, weight transfer is independent of the spring and anti-roll bar rates. The response of the car is dependent upon the spring and anti-roll bar rates but not the amount of weight being transfered.

mountainbiker2

Thanks guys for all the good information.
One change to my order. The 2812's that I ordered a week ago, I canceled. I'm back to looking at the 3013's. Right now I have the front spring installed and the back comes in Thursday. I'm going to see how it feels with the 04 Z06 shocks first. My first impression with the front spring is that it feels softer then my Z-51. The weird thing is when braking it dives less, but over bumps it feels softer.
When I get the rear spring on and re-align it, I will start a new thread.
Thanks.
Steve

froggy47

Guys that just throw a big bar on the front are just extremely misinformed.