Understeer problems

[Cone Basher]

I need better handling so it's time for a winter project and I need some recommendations:
This is my car:
FFR Coupe #118 , Motor Roush 402-R ,Tremac TKO 600, IRS with Tbird Sc 3.27 diff. Team III wheels 315 rear 275 front Hoosier A6 tires, 20-22 PSI front 22-24 rear
SAI mod with straight leg SN 95 spindles
Bumpsteer kit installed on top of the control arms
Manual brakes 13" Cobra front, North racecars upgrade rear, Hawk HP plus pads
Pro shocks (that came with the Kit)
600 lb springs front and rear.
VPM sway bars, front and rear, currenntly set full stiff
4 degrees of caster 1.5 camber on the front and rear, 1/8 toe in
Here are my questions;
1) How much caster can I run with manual steering (not a street car Auto-x only)
2) What spring rates? I'm thinking 800, 900, 1000 lb for the rear with the 600 fronts any ideas?
3) Can I run an 8 inch Eibach spring on the pro shocks?
I'm losing time in the turns because of oversteer,or old age, need help deciding.
Thanks to all for your recommendations:
CB

[CraigS]

Your title says "UNDERsteer problems" and then in the body of the post you say that you are losing time because of OVERsteer. I am lost for the moment.

[Cone Basher]

CraigS; I guess it's that old age thing or the bifocals need cleaning it's understeer I'm have problems with.
Sorry for the mix up:
CB

[trevor]

loosen the front bar or stiffen the rear springs (+100). Seems like you should have oversteer with what I read in your setup?

I wouldnt go over 4 degrees caster with manual steering.

You can dial in another degree front camber, that will help reduce understeer also. I run 2.5 neg camber with my A6s

[CA Crum]

Hey Terry, will be watching as I have the same issue.

I thought maybe for me it was inexperience and I am sure a chunk of it is.

mmarshall stated in another thread about running heavier springs front than rear, he has 700 front, 500 rear.
Little confused as Mark D. recommended opposite at heavy rear lite front, maybe for street?
Sorry to hijack thread, will be watching.
Chris

[itzdapig]

Mike is solid axle 3 link vs IRS

[Cone Basher]

Chris: If memory serves me correct mmarshal is running a solid axle car. I'm IRS which is bit different. What I think is going on is I have a higher roll center with the IRS and the outside rear wheel tucks up under the wheel well which unloads the inside front tire a bit. Looking for info on what iwill cure/reduce this problem.
Best of luck:
Keep in touch:
CB

[TNcoupe]

Scandanavian flick...... it'll rotate

it may not be the fastest but its damn sure the most fun, especially on gravel

[mmarshall]

As was mentioned my Coupe has a 3-link so it is different. I have been battling oversteer with matched tires front and rear. I did run an offset set of Hoosiers last season (8" front and 10" rear) and the car was very neutral. I am looking to stagger my tire sizes for next season. I am wondering if the 275/315 is too far split for a neutral balance.

I agree that your problem may be with the rear. My front end works very well so yours should also. I went to 700 front and 500 rear springs just to try to balance the car better and reduce the oversteer.

[Cone Basher]

mmahshal:
if it's any help I'm running 275 front 315 rears Hoosier A6 tires Team III wheels. What caster/camber set up are you using? I'm thinking of buying a longacre caster camber gauge set uo so I can adjust mine at home without going to an alignment shop. Initial turn is good but my problem is mostly mid corner and corner exit on very short turns.
Thanks.
CB

[M DOUGHERTY]

CB
the motion ratio of the rear IRS is different than the front. You need a stronger spring in the rear to get the neutral to over steer you are looking for.
You may want to try a 800 lb in the rear. then use the bars to fine tune from there.
I will go out on a limb here and say if you auto x a FFR with power steering you would change yours to power in an instant. It really is that much better. another thing you may look at is the rear brakes. I you may not have enough rear brakes. lack of rear brakes will induce under steer. If you cant induce over steer while trail braking then you dont have enough.
So to recap.
go to 800lb. springs in the rear.
get some more rear brake. call me and I can discuss the many ways to achieve that.
ADD POWER STEERING
also go to 1/8" Toe out in the front only. this will greatly help the car in the corners.
Later
Mark Dougherty
717-773-5624
Texting me works best

[Cone Basher]

Thanks Mark: I'm running Hawk HP plus pads and have plenty of braking on corner entry. I've been thinking about Fast Freddys power steering upgrade for my Coupe so I could run a lot more caster but I'm used to manual steering so I wanted to try stiffer springs in the rear as my first attempt to correct this problem. It seems to manifest itself more at mid corner and corner exit so I'm also thinking about the locker in my IRS. It's the stock T-Bird unit now which might be part of the problem.
CB

[M DOUGHERTY]

No problem
Another thing to try would be a little more tire pressure in the rear . Or raising the rear ride height

[mmarshall]

CB I run 9 degrees caster and 2 degrees camber w/power steering.

I also have a Torsen diff which helps turn the car under power. The track lok diff will tend to make you plow on corner exit vs the torsen turns the car under power. You might consider a torsen or true track.

Mark I am glad to hear your take on the rear brakes. I went to 94 Cobra 2 piston PBRs in the rear and am finally able to trail brake the car. My brakes now are fantastic! The standard single piston rears are only 50% of what is needed to achieve the balance that Mark mentioned.

Here is my brake mod thread: New brakes for the back

Be careful with the spring changes as too much of a change may turn your neutral corner entry into oversteer which will cause even more problems than you have now.

[Cone Basher]

Thanks guys, I think I'm going to start with 800 lb rears and a few more degrees of caster as a start and try to fine tune with tires pressure, bar settings, ride height. I have a print out of understeer/oversteer corrections on a lnik provided by Bob Cowan (thanks bob) so I have a number of things to try.
Happy Holidays:
CB

[CraigS]

A couple of thoughts. 1- caster will help some.Caster induces negative camber in the outside tire as the steering wheel is turned and since you are fighting understeer, we can assume your wheel is turned. But.. it will make the steering stiffer. I would go w/ 2.5 deg negative camber and leave the caster as is. Camber ( to whatever is max for the tire etc ) increases the tires steady state grip which is what you need and 2.5 is a common number among FFR autocrossers. 2- Get Fast Freddy's power steering. I would have done that if it had been available 5 yrs ago. What you may not realize is that more normal effort allows much better ability to catch and correct small needed changes as you go thru the turn. A few recent events w/ 5 cone slaloms has even made me begin to think about the faster racks although i love my 3.0 turns Breeze rack 98% of the time.3- Since you are fighting understeer, concentrate on front tire pressures. Most of us in the DC area are in the high teens. Get one of those old white shoe polish applicators w/ the sponge end and dap a spot about 1.5 inches in diameter at the edge of the tread. This allows instant decisions after one run. Watching the actual tread wear is way way too slow. If you look at the tire sidewall near the tread you will see several small triangles molded into the sidewall so they point at the tread area. The tip of those triangles is where you should be wearing your tread to. W/ 2.5 deg camber i run 18-19 lbs. in the summer when the tires are warm and we have good traction. In spring and fall, as temps/traction drops off i have been down to 16 lbs.HTH

[Cone Basher]

CraigS: I just purchased a set of Koni shocks with stiffer rear springs and softer front springs and I'm going to try to tune with these as a first step. My future Christmas presents do include Fast Freddys power steering as well as a different rear locker as I'm running the stock T-Bird unit. My car is a work in progress.
Thanks for you sugestions:
Happy Holidays:
CB