Suspension Voodoo

[wepsbee]

I am now trying to understand the voodoo racers call "suspension setup".
I truly understand suspension is undefinable due to its drivers "feel" component.
However there must be starting points.
Springs heavier in front or rear and why. Do spring lengths matter or can I
adjust the coilovers to make up the difference?
Camber in front and back, same camber to start prior to testing???
Car low as possible or raised, tight as opposed to loose?? Low car would seem to be faster but would the car be too tight with no give?

I know testing is king and will be attending a test day but I do not have unlimited
funds for testing or even tires so if I can glean alot of this info ahead of time it would help.
I assume most of you have gone through this so I am asking for some lessons learned.
Thanks

[Greg Amy]

Step 1: Buy a car that has a real suspension, not MacPherson struts.

Step 2: If no Step 1, then reach into pocket and buy best shocks you can afford.

Step 3: Buy stiffest springs Step 2's shocks can control.

Step 4: Realize this is stupid and go back to Step 1.

GA

[gran racing]

That goes contrary to the advice I've received Greg (besides step 1), but recognized there are quiet a few variables. When speaking with Lee at Koni about various shock packages, he actually recommended that I didn't purchase the "better" shock package due to diminishing returns. There were also other packages which had a multiple ways to adjust them which I simply am no where near ready for. Given my particular situation, having single adjustable shocks was the way to go. Koni also obtained various pieces of information about my car such as total weight, corner weights, and so forth.

What suspension brand are you using now?

[Greg Amy]

...speaking with Lee at Koni about various shock packages, he actually recommended that I didn't purchase the "better" shock package due to diminishing returns.

That's because he knows you're a cheap f**k...



On edit: sorry, I meant to use the word "thrifty"...damn Turet's keyboard...!

[Rabbit07]

Wow Greg, a bit cynical?
Greg is correct in most of this. However, if you are going to run a Strut type car there are things to be careful about. If you lower the chassis too much you can play hell on the roll center. This in-turn increases roll moment. With very heavy springs you still will not be able to keep the car from rolling or even jacking. You really can’t spend too much on shocks, but for IT racing you have to budget it. You can hit a point of diminishing returns so to speak. Most cars run more spring rate in the rear which seems to help. Ask a good chassis engineer and they will tell you it doesn’t matter once the rear tire is in the air. Once the tire is hanging you are at 100% weight transfer and the front springs are all that matters. Spring and shock lengths matter, you don’t want to bottom out or bind either one. Because you are fitting a poor camber curve you will need to run lots of static camber, but this will depend partly on tire choice.

[Greg Amy]

Me? Cynical? You don't know me too well...

Tell you one thing: had I kept the NX I'd have dropped a $6k set of Koni 2817 struts all the way around on that thing...and it would have friggin' FLOWN around Road Atlanta!!! Instead, I had to "make do" with custom-valved Koni 8611s (valving and spring rates, I might add, that Lee *still* doesn't understand how I made work)...

Just sayin'.

[raffaelli]

Step 1: Buy a car that has a real suspension, not MacPherson struts.

Step 2: If no Step 1, then reach into pocket and buy best shocks you can afford.

Step 3: Buy stiffest springs Step 2's shocks can control.

Step 4: Realize this is stupid and go back to Step 1.

GA

I LOL'd.

[924Guy]

I think it was Sir Colin Chapman who once said "any suspension can be made to work well once you stop it from moving." Most appropriate as relates to struts...

[rsportvolvo]

The suspension is only a means to keep the tires happy. Learn to read tires and you'll be steps ahead of the competition.

Set camber based on tire temps across the tread
Toe is for tracking and turn-in (toe-out front, toe-in rear generally)
Caster is suspension layout specific. Struts require more caster to work (emulate BMW & Porsche if you have struts).

Depending on your technical background and desire to play with numbers you can read up on suspension design via Milliken's, Rowley's, Puhn's, and Smith's books.

One caveat to Greg's comment on dampers & springs. A damper only works when it's moving. If you are sprung as stiff as a go-kart then dampers really don't matter that much.

[chuck baader]

A couple of comments..first, a strut car can be make as fast as an "a" arm car. Second, front drive cars like a lot more spring than a rear wheel drive...something esoteric about keeping the inside front wheel planted. Third, shocks, shocks, shocks...talk with Lee at Koni until he gets tired of you. He should have a good deal of knowledge of spring and bars from the old escort series. CB

[wepsbee]

I have spoken to Koni and last year purchased a set of 8600 series Double adjustable shocks put together by Koni USA. They made a tremendous improvement but I think not enough.
I have 500 6" Eibachs in the front and 400 7" Eibachs in the back.
I just installed rear camber plates and have not yet had the car on the track so the test day is going to be busy.
The car to me feels a little whippy and rolly, New technical terms, so I thought stronger springs might be in order.
I experience some understeer in tight corners.
I will be using up a set of TA-1's and 888's then I will be using Hoosiers.
Will the setup be different for different tires??
BTW great help by all, Thanks

[lateapex911]

The set up will most absolutely be different on Hoosiers than the others. I'd recommend NOT using the TAs..just toss them, you'll end up chasing your tail. And i know you don't want to hear this, but I'm thinking the 888s are a waste too, if you're trying to dial the car in.

If you can buy Hoosiers in your size that have some cycles, that would be better. Of course, you'll still have people suggest that setting a car up on used tires is a waste, but, it's better than setting it up wrong...and I imagine you won't be putting fresh ho hos on every other session, so.....