steve40th

Seems to me, everything stock is not stiff enough, along with shocks.
SO my question is, when does a spring become to stiff in autoX?
Do you want the spring to allow some lean, and let the alignment and tires do the rest?

0RAAMaudio

I am new to the Vette scene but pretty experienced in autocross with all types of drivetrains and have always preferred moderate springs, adjustable sway bars and the fattest, softest tires I am allowed to run in the class.

Plenty of negative camber, positvie caster, probably some tow out front and rear, may be the way to go, have not had the change to test yet, not for a few months here in Utah.

So, just general thoughts for now, more into track days and building up to road race now but I will run autocrosses because I like them and I can get my kids more involved(the main reason, keep them off the streets, teach them to really drive


Whatever you do, use light wheels!!!!

Rick

mrwrenchphd

When it won't let you utilize all of your suspension travel in the conditions you normally drive/race in I would imagine. I thought my springs were to stiff in my track car so I put zip ties (some people use rubber bands) on my shock shafts & after the track day looked to see how much travel was used. Even with a wheel rate of 495lbs. it used it all. So I felt good about my set-up.

steve40th

Neat trick. I might try that with the FE1 93.3 springs then the 115.7 ZO7 springs to see the changes.

0RAAMaudio

Yes, zip ties, etc, very good testing tool

Softer springs can help keep the tires on the ground on rougher surfaces, bumps, etc, more contact, more grip, more speed

To soft, bottom out, lose grip and other issues.

There is a more accurate but more time consuming way to determine optimal spring rates, damper settings, etc. it has to do with frequency, I will address that once the season gets rolling.

Rick

steve40th

Can you explain, or with pics, where to put zip ties and utilizing them.

samc

i have a picture of what too much rear spring can do...
http://gallery.floridacorvetteracing..._0703_173604AA
there are a lot of factors that will dictate the required spring rate, but in my case i had WAY too much spring, and it made the rear "loose", so when i tried to turn a little too fast in a slalom, the rear came around on me. ended up down a hill then up a tree... but i did learn a lot. got a softer spring from VBP, and now the car is much more competitive. (so, the body panels are different colors now, at least i washed the berry stains off...) http://gallery.floridacorvetteracing...all05/IMG_1068

jwt1603

Hey Sam,

Are you guys doing the Tampa Fairgrounds this year? When is the next time you're running a sanctioned event at Brooksville?

Joe T
North Florida Corvette Association

TheNick

Zip ties are useless the second you hit a bump. If you drive on a perfectly smooth sheet of glass with zero jacking forces from the steering - then you can consider them a good tuning tool.

Springs are too stiff when the suspension looses the ability to remain compliant over bumps.


There is nothing wrong with lean. Load transfer is completely dependent on the dimensions of the car. Track width and CG height. The lower the car - the less load transfer - the lower the car - the stiffer the car needs to be to remain off the bumpstops.

steve40th

Good Lord, what spring rate did you have? Were you trying to make the front end come up druing tunrs?

davidfarmer

All above sounds good. If you are driving on a laser-level-smooth surface, then maybe you could drive without springs. I used to see a lot of slammed hondas running around town with no springs in them. They BOUNCE around just like a track car would, with the tires literally leaving the ground every time they hit even the smalled bump.

Tires are springs also, and allow some compliance, and in an F1 car, I'd bet the tire is "softer" than the actual springs. However, in road cars, you want the suspenion to be compliant to bumps, the inside tires to droop in corners to aid in grip, and you want the weight to shift in a smooth controlled manner.

TheNick

If you are driving on a smooth surface - you still have load transfer when you turn. I bet those Honda's had springs on them - I bet they were super soft, super low and way out of the operation range of the stock shocks they were using. Thats why they were bouncing around all over the place. There is a difference in bouncing because of a lack of damping and bouncing because there is no compliance in the suspension.

BTW - weight never transfers - it is always a downward component at the CG. The term you are looking for is "load transfer"

bsim

Uhhh, isn't the point TO hit bumps? To see how much travel is being used?

rfn026

You shouldn't be using springs to control body roll. You control body roll with the sway bars.

Springs, shocks and sway bars all have different purposes. The real job of the spring is to keep the car from dragging on the ground. Today you really want the softest springs you can find - and the biggest sway bars you can locate.

On the other hand a Kuhmo engineer once told me that if I got the car totally screwed up and it became impossible to find the sweet spot just put stiff springs in it and "run it like a damn go kart." He said that stiff springs will cover up all sorts of bad settings.

I run the base springs in my '85 and Z51 bars. Bilstein made me up a set of custom shocks. Now if I can get more negative camber into the damn thing I'll be fine.

Richard Newton

Autocross Performance Handbook

Wheel and Tire Performance Handbook

Bill Hetzel

Yea, you're right about the tries/springs on a F1. Springa on an F1 or Indy car are unbelievably stiff.
Even the spring rate on a Formula E is high. We run 600 and 1000 springs on an 1100 lb. car.
Davy Jones, from Indy cars, did some testing on these cars when we changed to Penske shocks and said he was supprised how soft the cars were, so you know the Indy cars are extremely stiff.

steve40th

So soft springs, big sway bars and custom shocks with plenty of camber and sticky tires. Stiff springs arent doing you any good?
Then why does everyone use a ZO7/Z51/ZO6 etc. Just get a base suspension, get big bars and an alignment?

rfn026

Most of the ZO7/Z51/ZO6 cars are street cars. That's a whole different agenda.

Richard Newton



Autocross Performance Handbook

Wheel and Tire Performance Handbook

steve40th

True. I am working that agenda, as I know alignment and sticky tires are the big helpers. I will not be running real competition tires for a while, but I do run BFG KD's. My videos dont really show allot of body roll with the ZO7 sway bars I have and QA1 shocks. But I will be putting my ZO7 springs on here soon, and then a good autocross alignment, which is no biggie here in Hawaii as I barely drive the car anyways.

samc

hi joe - we have 10/25 & 10/26 reserved at brooksville. still trying to get back at the fairgrounds, and now we are talking to some people with a track in bradenton. if they get their zoning straight we might be able to do something there earlier in the year. i was going to try and get an early date at brooksville, but due to a miscommunication we didn't. we will have some non-sanctioned events there starting back up in may.

steve - i don;t remember exactly, but i think gary said it was 750#/in - seems there were some mislabeled springs at vette brakes. gary took care of me though, and got me the right spring - and it made a big difference. i think the new spring is maybe 350#/in. not only do i stay on the track now, i noticed almost 2 second improvement on a ~50 second autocross course. that was at the fairgrounds, and the course was the same. i could be way ff on the #'s, i would have to check with gary.

mousecatcher

that's the opposite of my understanding.

you want the stiffest possible spring, to control dive and squat. you want the softest possible sway bar, because the stiffer the sway bar (which only exists to make up for inadequate springs) the more bumps in a corner upset your handling (by transferring energy to the opposite wheel).

in a street car, you give up too much in ride quality if you use springs that are too stiff, so you have to compromise with sway bars.

formula cars have very little sway bar. some none at all.

just as an example, if you add more rear sway bar, the car gets looser. this is because more load is transferred from the outer wheel (where the grip is) to the inner wheel.

of course my advice is worth what you paid for it.