maybe too much oversteer .. options?

Topic: maybe too much oversteer .. options? (Read 2337 times) previous topic - next topic

maybe too much oversteer .. options?

April 26, 2009, 08:51:45 PM

Last time at the track, it seemed like maybe the car was a little too tail-happy, maybe. Right now I'm just thinking about options. Car has the factory front bar for a TC (IIRC, 1.31") and the factory rear bar for a Cobra ('03-'04). I'd like to compensate by increasing grip in the front, instead of decreasing in the rear. Also, I'm planning on going with softer springs (right now 350 lb/in & 550 lb/in f/r), hopefully something closer to a rate that equates to the FMS springs (~250 lb/in in front?) If I go with 250s up front, that equals about 400 lb/in in the rear, if staying proportional to the current combination.

Questions:
Did the factory go to a smaller rear bar for the later year Cobras?
Is there a bigger front bar that will fit, factory or aftermarket?
Any suggestions on a different spring rate combination?

testing title change

Reply #1 – May 03, 2009, 06:16:59 AM

any ideas on the a/s bar?

maybe too much oversteer .. options?

Reply #2 – May 03, 2009, 09:11:59 AM

If the car is tail happy wouldnt you want More traction in the rear??? not the front???? Then again, i dont go to tracks (mainly cause of the lack of them)........

maybe too much oversteer .. options?

Reply #3 – May 03, 2009, 10:50:26 AM

AFAIK, all IRS cobras had the same 1" rear sta-bar.
i think steeda makes a 1 3/8" front bar. would be just a bit larger than your current 1 5/16"
250lbs coils sounds really soft for a car you open track. why are you thinkin about runnin softer springs?

maybe too much oversteer .. options?

Reply #4 – May 03, 2009, 12:07:36 PM

I know this isn't super helpful in answering your suspension questions, but I would corner weigh the car and see what could be done to optimize corner weights. Next, (assuming near optimal suspension setup) I would see how much +/- steer can be found by playing within the recommended pressure range of your tires. once the benefit of these two concepts has been realized (assuming they aren't already) I would then go forth with more mods.

maybe too much oversteer .. options?

Reply #5 – May 03, 2009, 01:37:49 PM

ahhh gumby made some sense of it for me.......

maybe too much oversteer .. options?

Reply #6 – May 04, 2009, 03:01:43 AM

Gumby,

I talked with somebody at MM this week, somebody more knowledgable than when I was putting things together. It appears that I don't have enough suspension travel, especially droop, and that's the reason for the rough ride, not the spring rates.

I'm going to try getting things adjusted this week, but the solution may require some work. There's not much room to move the coilovers downward. I was thinking about slotting the strut mounting points to move the top of the spindle away from the strut, then using the CC plates to set the camber properly. That might provide enough clearance for the tires. I won't know until I get under there and measure.

Question: will that screw up the suspension geometry?
Question: is there another way to get more travel? Maybe some adapter plates to locate the strut higher relative to the spindle?

maybe too much oversteer .. options?

Reply #7 – May 04, 2009, 03:05:47 AM

massCougarxr7,

You buttstuffyzed the problem correctly, if the car is tail happy, then the rear is (probably) stiffer than the front. The important thing here is the relative nature. The ways to compensate for the problem are
a) increase traction in the rear (I'm considering widening the rears)
b) soften the rear
b) stiffen the front

ASSuming the rear isn't too stiff, then cornering gains could be gotten by stiffening the front, or increasing traction in the rear.

Somebody can step in here if I've gotten something wrong.

maybe too much oversteer .. options?

Reply #8 – May 04, 2009, 06:44:19 AM

too little droop in front? fox mustang struts i assume?
from my understanding, keeping the most positive relationship between the spindle and the strut will improve your geometry. therefore, its better to adjust at the top and not slot the strut ears for negative camber. i dont know if going the other way, more positive at the bottom, would fall under "more is better" or not. ive never seen a car that had enough adjustment at the top to try it.

what is your ride height?

maybe too much oversteer .. options?

Reply #9 – May 04, 2009, 12:01:09 PM

Quote

too little droop in front? fox mustang struts i assume?

Yup, because of the spindles. And because they're later versions, they actually reduce the travel more than the older ones do (spindle mounts relatively higher).

The problem isn't the ride height (I guess about 5"), but the wheel/tire position to the strut. There isn't much room to drop the lower spring perch. There is no way to fit the coilover between the strut and tire.

And yes, you're right, those ears don't leave much room to operate.

maybe too much oversteer .. options?

Reply #10 – May 04, 2009, 12:10:24 PM

Perhaps you're getting some odd rear steer?

We did some mods @ KB's to allow for better rear "bump steer" adjustments.
Gumby, your IRS rear has the modified inner tie rod mounts, correct?

maybe too much oversteer .. options?

Reply #11 – May 04, 2009, 12:29:29 PM

that is a good point as well. yes, mine does have the modded inner mounts.

skidoo, have you measured your rear bumpsteer?

maybe too much oversteer .. options?

Reply #12 – May 04, 2009, 02:40:38 PM

I have not measured it. The alignment shop might have, I'll check with them, see if they remember.

I do have the adj tie rod ends and the a/s bar end links.

What did ya'll do to modify the inner mounts?

maybe too much oversteer .. options?

Reply #13 – May 04, 2009, 02:49:27 PM

Quote from: t3skidoo;270480

What did ya'll do to modify the inner mounts?

Added some more adjustment down. The brackets were widened by something like 3/4" (It's been at least 8 years, so I don't remember the exact measurement) to allow for more room to adjust.

We replaced inner stock tie rod end with a std spherical piece. (The rod was also replaced with a new rod as well, I think I touch longer as the aftermarket rod ends were shorter than the stockers)

maybe too much oversteer .. options?

Reply #14 – May 04, 2009, 04:07:17 PM

I don't suppose you have a visual aid?