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FB suspension set up help request.

Old 08-23-07, 01:02 PM
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FB suspension set up help request.

I have an 85 GSL that I race autocross in CSP.

The set up is...

Tokico Springs, I have no idea the rate, they were on the car when I bought it.
Tokico lumina on fount an HPs on back.
Racing Beat roll bars. (rear currently disconnected)
ReSpeed camber plates set to ~ -2 degrees (all I can get with current springs)
225/50/13 A3 Hoosiers. Normally run around 35-38 psi
The LSD is very tight and locks very easily.
The toe in is set out 1/16-1/8, I have been told to change this to a little bit of toe out which will help with initial turn in but would not cause understeer.

At the last even during steady state turns such as a sweeper the car has gross understeer. I figured I was overdriving in to the turn but I had one of our local hot shoes drive the car and he said the same thing. If you apply any power during a turn the front end gives away. The car has a very neutral feel other than this problem.

Any suggestion would be appreciated.
Darryl
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Old 08-23-07, 02:38 PM
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Was it understeering with the rear swaybar disconnected?

See if you can find out what rate the springs are. If there isn't enough spread (rear too high or higher than front, or front too soft) it can cause understeer and be hard to find.

What about tire pressures? Any differential front to rear, and how much?
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Old 08-23-07, 02:51 PM
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Rear sway is disconnected. I guess I should have added that the car would snap over steer with the rear bar connected, I think the watts link would bind, the spring rate would go infinite then the rear end would come loose.

I have tried the front and/or rear tires from 34 to 38 psi with no change.

I have never been able to find out anything about the springs, they are Tokico and are marked "5050".


Thanks for the reply.

Last edited by engled; 08-23-07 at 02:58 PM.
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Old 08-23-07, 03:37 PM
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Chances are the springs are the old stiff front soft rear to work with the Racing Beat bars. The RB front bar is basically a solid axle conversion kit that does pretty well taming the car.

The stock rear end set up is like having one foot in a bucket, the huge front bar is like putting your other foot in a bucket so you feel balanced when running.

The watts link doesn't bind, its the upper links.

I think some toe out will help on an auto-x course. Possibly a little more front camber if you can do it. I've seen guys run a ton of neg camber and still go fast with similar set ups.

You might try to find some rubber spacers to fill in a coil in the rear springs to increase the rate. Check on the circle track sites since the springs are 5" dia.

Before you buy ANYTHING for the car buy the GForce Engineering set up book. It will save your from spending money two or three times on parts and teach you what is really happening under the car.http://www.gforceengineering.net
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Old 08-23-07, 09:14 PM
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I second the suggestion on the G-Force book. Best of all in comes with unlimited access to Jim Susko, suspension engineer and two time SCCA Nat Chap. $75 is so cheap in relation to what is saves for you (in time and money).
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Old 08-23-07, 09:24 PM
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I had gross understeer when the front struts would run out of travel and bottom out on the bump rubbers. Caused by having the front too low.
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Old 08-23-07, 09:40 PM
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Originally Posted by engled View Post
I have tried the front and/or rear tires from 34 to 38 psi with no change.
What pressure differential are you running front to rear? Even? On the Spec7's (stock suspension geometry with Tokico shocks TMC springs, big RB front bar, no rear bar) I have to run a 2-3psi difference to make up for the rear bar.
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Old 08-23-07, 11:41 PM
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Darryl,
My blk/wht RX-7 handled horribly up until a couple of years ago. I decided to do the coil over conversion and after a couple of spring changes - I was quite happy with the car. I already had a Koni front bar, removed the rear bar, and drilled holes in the rear upper control arm bushings. The car really came to life though when I got the springs right and got decent tires. The was all before I acquired Captain America.

How many heat cycles on your tires? How much rubber you got left. If your tires are dead - you can chase your tail trying to make the car go faster. I bought my coilover kit off of ebay for like $20 shipped. It's a Miata setup. You can try using the short springs that come with it. I bought my rear springs from ISC. I requested 150# springs. They measured 170#. My front springs are 400-450# I can't quite remember. I don't autox quite as much anymore so I replaced them with some other springs I had (maybe those Miata springs - which I measured at 400#f and 325#r).
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Old 08-23-07, 11:57 PM
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I third the G Force Tuning Manual suggestion. Just do what is says - spend the money - the result is a faster car.

For grins here is my IT road racing setup:

Front

400lb 7" Swift coil overs (very light)
Koni Single Adjustable racing struts (pt# 8610 I think)
Racing Beat sway bar
1" spacer under strut - no akerman correction
Ground Control camber/caster plates
Spherical bushings in the lower arm
3 degress negative camber
1/16'' to 1/8" toe out

Rear

250lb rear springs
Pro Shocks Pt# WB735 (really cheap @ $50 each!)
No rear bar
Fabricated Pan hard bar - no watts link
G Force Tri Link
Spherical bushings in the lower control arms

Tires - Kumho V710 215/50X13

26-27psi cold - 35-36psi hot - Hoosiers need more pressure and work best at aroung 38-40psi hot. I set cold pressures the same front to rear. I will vary pressures side to side depending on the race track.

In the past I have used 450lb front and 300lb rear springs with Tokico Illumina all around. The car works better on the softer springs in my opinion.

For solo 2 I would add more rear rate - never run a rear bar - and install Jim Susko's akerman correcting spacers.
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Old 08-24-07, 12:17 PM
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I think the tires have around 35 heat cycles/runs on them, one of them just started showing cords. I don't recall the car ever being this bad with fresh rubber even with the rear bar attached, could the A3s give up that quick? the grooves in them are pretty much gone. I have a set of fresh V710s being dropped of today I loved the Hoosiers when they were fresh but if thats the problem it would make since.


Originally Posted by slowautoxr View Post
Darryl,
My blk/wht RX-7 handled horribly up until a couple of years ago. I decided to do the coil over conversion and after a couple of spring changes - I was quite happy with the car. I already had a Koni front bar, removed the rear bar, and drilled holes in the rear upper control arm bushings. The car really came to life though when I got the springs right and got decent tires. The was all before I acquired Captain America.

How many heat cycles on your tires? How much rubber you got left. If your tires are dead - you can chase your tail trying to make the car go faster. I bought my coilover kit off of ebay for like $20 shipped. It's a Miata setup. You can try using the short springs that come with it. I bought my rear springs from ISC. I requested 150# springs. They measured 170#. My front springs are 400-450# I can't quite remember. I don't autox quite as much anymore so I replaced them with some other springs I had (maybe those Miata springs - which I measured at 400#f and 325#r).
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Old 08-24-07, 12:52 PM
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Originally Posted by engled View Post
I think the tires have around 35 heat cycles/runs on them, one of them just started showing cords. I don't recall the car ever being this bad with fresh rubber even with the rear bar attached, could the A3s give up that quick? the grooves in them are pretty much gone. I have a set of fresh V710s being dropped of today I loved the Hoosiers when they were fresh but if thats the problem it would make since.

I would try the new tires before making changes. Also, have you put a parameter on the tires after a run to see if you are running the correct camber up front?

-billy
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Old 08-24-07, 01:00 PM
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Yes I did check a couple of races ago, the numbers were very close all the way across. I did not check at the last race as we didn't have a parameter handy.

Thanks to every one for the advice.



Originally Posted by bwaits View Post
I would try the new tires before making changes. Also, have you put a parameter on the tires after a run to see if you are running the correct camber up front?

-billy
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Old 08-24-07, 02:02 PM
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HA! I'm almost afraid to let you hear my setup but here goes:
Front: homade coilover kit with 150lb springs, ebay camber plates set around 2.5 degrees, 3 piece 1.125" stock car sway bar, Tokico Illuminas. I have to keep the ride height close to stock to keep from bottoming out the shocks under breaking.
Rear: aftermarket 100 lb springs I found in one of my parts cars, Tokico Illuminas. Everything else totally stock with original 200k mile old rubber bushings. The only other thing I did was replace one of the rear sway bar links with a threaded rod so I could neutralize the bar.
I have the stock GSL SE wheels with Khumo 205 14 V700 or V710 rubber. I also added a shim to the clutch pack in the limited slip so it's darn near totally locked up.
The car is very well ballanced and forgiving with this setup. It easily holds it's own against Spec Miata's and the like. With my budget, that's all I'm looking for.
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Old 08-25-07, 09:14 AM
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I have a simaler setup to above, but I have tokico HP on all 4 corners. I have no camber plates, and my alignemnet is fubar. I also run no name brand bs tires in p175/80/r13's lol. (tire are amasing inteh rain, but suck everywhere else).

I noticed I can either set the car up to do all the tight cornering in Autox, or the larger sweepers. I usualy set the car up for the tight corners, and understeering like mad in the sweepers, like the problem you had.

I noticed my FUBAR aalignments had alot of toe in. Way to much toe in. However I think the problem is more rudamentry then that.

I think that the problem is driving technique (at least in my case). I noticed that in tight corners I would be doing hard braking just before the corner, and into corner entry. This shifts the momentum of the car such that the car is more tail happy. To stop from kicking the back end out on every corner I reduced rear tire pressure. This creates more understeer.

When I would go into a sweeper I would typicaly be hard on the throttle and thus the understeer correction from above would cause understeer problems. I solved the problem by hamering the throttle more, and forcing the back end to come out. Some times I find my self ina full 4 wheel drift. Other times the back end is just comming out a tiny bit, and it works perfectly.

Try the new tires, and see what happens. If the problem is still their mess around with your braking, and turn in points, and tire pressures.

Good luck!
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