Trying to understand chassis tuning

[rick88civic]

More on this subject. I am running a 1990 ITA Civic with Koni shortend, and valved. The problem is bottoming the suspension, specifically the left front upper balljoint hitting the tower. Hit with 1000# springs in front, no front sway, progressive in back with 800# springs, 5 1/2 " ride height. Springs to stiff car bounced. Raised car to 6 1/4 dropped to 800# front and 600 # back. Still hit left front balljoint but not as bad.
I would like to keep this spring setup but the car will not rotate under these conditions. I don't want to put the front bar on because of a bad push. If I lower the car, hence lower the CG the car should not roll as much but I am afraid of bottoming again. This happens on hard rights. How can I fix? I cannot drastically change corner weights but would this help. HAs anyone installed sway so that it does not catch until car rolls to a certain point? Might be snappy when that occurs. Thoughts?

Rick Jarrett
ITA racer

[Xian]

More on this subject. I am running a 1990 ITA Civic with Koni shortend, and valved. The problem is bottoming the suspension, specifically the left front upper balljoint hitting the tower. Hit with 1000# springs in front, no front sway, progressive in back with 800# springs, 5 1/2 " ride height. Springs to stiff car bounced. Raised car to 6 1/4 dropped to 800# front and 600 # back. Still hit left front balljoint but not as bad.
I would like to keep this spring setup but the car will not rotate under these conditions. I don't want to put the front bar on because of a bad push. If I lower the car, hence lower the CG the car should not roll as much but I am afraid of bottoming again. This happens on hard rights. How can I fix? I cannot drastically change corner weights but would this help. HAs anyone installed sway so that it does not catch until car rolls to a certain point? Might be snappy when that occurs. Thoughts?

Rick Jarrett
ITA racer
[/b]

Sounds to me like the issue isn't in spring rate but instead in bumpstop length. How much of the stock bumpstop do you have on the front left corner? You should be using just over half of it... any less and if you hit a big enough bump, it will cause the upper control arm to hit the frame. FWIW, I had my car set up by OPM and am running 500#F spings without any push or bottoming problems (also on shortened/revalved Koni's) with no front bar.

Christian

edit:
are you running a rear bar? Also, have you looked into running a softer front rate and stiffer rear rate?

[rick88civic]

Full bumpstop in place.

[mattbatson]

Now, I'm not running a civic...but a suzuki swift.

It is a fwd though, so same principals may apply.

I am running stiffer springs in the rear then the front. My koni's are also adjusted almost full stiff on the rear. And much softer rebound for the front....
I run a stock rear bar, and no front sway bar....

Even before the welded diff, I had no problem with rotation...(open diff)
Now with the welded, it handles like a RWD :P plenty of rotation...

I also dont have it lowered as far as possible...I rarely hit the bumpstops.

This set up has been pretty effective so far, as I rarely give up anything in the corners...
So, perhaps trying softer front and stiffer rear is a method to try? And, maybe raising it all around half an inch?

[Xian]

Full bumpstop in place.
[/b]

Weird. Are you positive that the upper ball joint is hitting the shock tower? Are you able to see the "circle" mark that it leaves or is it something that you're just hearing from within the car?

I'm running about a half bump stop on both front corner without excessive bottoming problems. Yeah, if I really pound a curb i can hear it bottom out and every once in a while the upper ball joint will hit the shock tower but it's not upsetting to the chassis.

RE: the lack of rotation. I imagine that a large part of this is due to the spring rates front to rear and the rest of it might be due to the low-ish ride height in the rear (too much camber as a by product of ride height). My car also has a fair bit of rake in it's setup (front ride height 5.25" at the rocker panel and 6.25" rear). 500# front springs 700# rear with no front bar and a 3/4" Suspension Techniques rear bar. Maybe try significantly increasing the rear roll stiffness and decreasing rear camber to get the rear end to loosen up.

As always, my $0.02.

Christian

[rick88civic]

Definitely is hitting nice imprint in tower. A little more bar in back I don't think will make a difference. I am already lifting inside tire off ground at entry all the way to exit. If I raise the back I will be moving the CG towards the front, which will load the left front tire even more.

[Xian]

Definitely is hitting nice imprint in tower. A little more bar in back I don't think will make a difference. I am already lifting inside tire off ground at entry all the way to exit. If I raise the back I will be moving the CG towards the front, which will load the left front tire even more.
[/b]

I understand that raising the rear will shift grip forward but in doing so it will also loosen the car up for you and should get rid of the push you mentioned initially. I'm really not sure why you're having the problems with bottoming on the front... other people I know running similiar setups to mine on the 88-91 Civic chassis don't seem to have excessive bottoming problems either

[rick88civic]

I have also talked to other people who do not have a problem of bottoming. I did run a heavy spring in back on a good smooth track but the track i have been running the heavy spring made the car bounce all over the place, although it was fast it was handful with plenty of rotation. By shifting weight forward i would think it would load the left front even more were it would go beyound the tires grip capability. The push in the car with the current setup is probably the best it has ever been. I thought of raising the left front hence putting more weight on right rear and get the rotaion by putting more bar in the car. The only problem is that by raiseing left fron the static load would be greater on that tire but the transfer should be less. Actually raising the left rear would transfer weight to right front which should give beter front end bite and loosing the left rear for rotation. Any thoughts?