Please help me diagnose and correct the suspension setup of my car.

The symptoms: the car is very ragged near the edge. It does not break away gradually. It oversteers quite a bit on even slight throttle lift. It does seem to recover from being out of shape if I stand on the gas, but in some instances that is just not an option (like a decreasing radius 180* turn. I notice the problem mostly mid-corner. I want the car to warn me before sliding into a spin and give me other options besides full throttle to save it.

The setup: Stock power-train, BC coilovers (BR series) with 8kg/mm front and 10kg/mm rear springs. It is not corner balanced (please propose fixes besides corner balancing, I can’t get that done in the near future)

Ride height:
When I measure form the center of the wheel straight up to the bottom of the fender lip, it is 14.5 inches in the front, and 13.625 in the back (so bigger fender gap in the front). However when I measure from the ground to the “jack point” (where the stock spare tire jack would go), it is 8.5 in the back and ~7.5 in the front (so lower in the front than back). From side to side the ride height is within about 1mm.

Alignment:
Camber -2 front, -1.5 rear.
Toe: 0 front, whatever Mitsu spec is in the rear
Max caster

The car was on stock Advans. I got the car to be the most manageable by stiffening the damping in the front to 10 clicks from full soft, and softening the rear to 5 clicks form full soft. I never did get hot tire pressures, but cool I had 30 in the rear, and 33 in the front.

Tire wear was excellent, with slightly more wear on the outboard half of the tires. No rollover whatsoever. Body roll was very acceptable. The car is fast, but difficult to manage near the edge. I am a beginner/intermediate DE driver.

EDITED FOR PROPER SPRING RATES

 

What have you changed in the way of sway bars or bushings?

 

no other changes besides the addition of coilovers. I was hoping that with the appropriate spring rates I caould forego changing the sway bars.

I'm hoping theres a setup solution that doesn't involve throwing further parts at the car.

but with my luck, I'll need 3 more mods to correct for the first mod, and then 2 more for each of those... :sigh:

 

Call http://www.robispec.com/ he should be able to straighten you out. Mr. Fuller won't BS you.

 

Seems like your rear spring rates are little too stiff. I would put 8K springs back on the front and see how that works. Just my .02c

 

Yeah....your springs rates are interesting. I might even go with just 6k/8k if you're on the stock advans and plan on learning the car with them. Then maybe put the 8k spring up front and put that 10k back on the rear when you're ready.

Check your rear toe too.


- Andrew

 

I agree that the rear rate may be a little much compared to the front, but you should be able to improve the balance through tire pressures, shock settings and alignment. What is the actual rear toe?

 

+1

Definitely find out the actual rear toe.

With a good damper, you may be able to tune out some of that oversteer.


- Andrew

 

^ +1

Also Read this:
http://www.ozebiz.com.au/racetech/th...hocktune1.html

But in general it seems your rear spring rate is just way to much higher than the front.

 

JUST RE-READ MY ORIGINAL POST, AND I FAT FINGERED THE SPRING RATES.

I have 8k on the front and 10k on the rear.

sorry about that!!

 

part of the reason I am gathering recommendations is that I am going in for a re-alignment.

I am thinking more rear camber, at least -1.8 to -2 if I can get it.

what is a good rear toe setting?

Also, what about my ride height? Am I way off? I can set that before going back for the alingment.

 

I am sure he wouldn't. However I've never bought anything from him, so I'd feel awkward asking his advice just out of the blue.

 

Don't take this wrong way, but what makes you so sure that it's a mechanical (set-up) problem rather than technique problems? Just curious...

 

double post, please ignore....

 

definitely not taking it the wrong way.

What I am trying to get advice on is how to set up the car to be more forgiving of my not perfectly developed technique.

If I never made a midcorner correction I wouldn't have a problem. however I do sometimes need one (steering or throttle), so it would be nice if I could get the car setup to be a little more gradual in its breakaway, instead of sliding the back out and threatening a spin everytime I mess up a little.