wheel rates
 

Open trackers, what wheel rates are you guys running in roll(springs and sway bars)? I have been going stiffer and am now running 385 at the front and 335 at the rear. It seems pretty stiff to me. I was just told that most race cars wind up at wheel rates close to corner weights. That would be 650 pounds a corner for me. An experienced race car chassis set up guy in Phoenix told me that. Ant wheel rates or comments? Scott

With certain other factors assumed you do want you wheel rates to follow your corner weight or weight distribution. The numbers you have listed are of course your spring rates. Bias your wheel rates slightly forward to help prevent snap oversteer.

So you do not run wheel rates at the corner weights. That would be big time over kill. You may run spring rates at the corner weights but that would just be coincidence since the spring rate is basically irrelevant unless you are compairing two identical cars. Wheel rates in say the 175-200 setting are firm for street use. Up to 250 for track. But of course this is a big 'depends'.

Frequency might be a better way to determine a starting point on spring rate. And of course this will change for every track. 80-100 CPM for a firmer sports car and 100-125 CPM for a racing car without wings or ground effects.

Basically I would set it up with the softest springs possible so long as it kept the thing off the ground and established the basic balance of the car. This keep tire compliance high. Then use bars to keep the camber curves under control. Do a little math and come up with a front and rear bar size after you come up with a base line spring rate and make your rear bar adjustable. Don't make tiny changes in spring rates. About 50 pound steps is about right.

Shocks to tune the rest.

Hope this helps.

Rick

Rick, those are my wheel rates in roll for front and rear, not spring rates. The spring rate in front is 600 pounds with a 1.25 sway bar. The rears have 800 pound springs and no rear bar. I know the spring rates don't matter because of motion ratio's, just the wheel rates. The balance is 53% front and 47% rear at the wheel. My vehicle weighs 2600 pounds with me in it, static weight distribution at 51% rear, 49% front. The load transfer on acceleration accounts for the lesser static rear wheel rates. I used to run softer wheel rates. The problem was that the cobra with its narrower front track, would not turn in well. I think it just fell over. Now it turns in really well. I am concerned with race track only. Scott

Scott,'

I don't know if this will help but here is what I have:

1 1/8" front swar bar
600# front springs
5000# rear springs (no swar bar) Couldn't keep it on the track w/ rear sway bar.

However, I am thinking back to Road America last year and your track times were so much better than mine and I am wondering why you want to change your setup? Granted the driver makes a very big difference on that track. It took me couple days to get where I could run flat out on the straights (especially the back ones with the cement walls and trees).

Looking forward to seeing you at Road America again this year.


Clois

Clois, I wanted to change it because my cobra would not turn in well. I noticed this when following some other cars at road america. Opposite of what you might think, to get a cobra to turn, a stiffer front was required. I am happy with my times but I felt like I was fighting the car at entry to every corner. I will be there again this year. Scott