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Still oversteering

Old 05-16-04, 11:26 PM
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Still oversteering

Ran my first autocross of the season today. Had a good time, the car ran well. It's a 79 weighing about 2000 lbs. But, after trying a stock rear bar, and the adjustable Suspension Techniques bar, I completely removed the bar. It is still oversteering too much. I'm running 5 way Tockicos set on 1 in the rear, 4 in front. Racing Beat coilover conversions, camber plates and extended control arms in front. I have Eibach springs all the way around, shortened in the rear. I've adjusted the tire pressure (Victoracers), with limited improvement.
Whenever I get brave enough, I will order the slicks and wheels I can legally run in Prepared. That will be an entirely new challenge.
Any suggestions in the meantime?
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Old 05-17-04, 01:08 AM
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your driving style is probally attributing a lot to your oversteer
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Old 05-17-04, 07:20 AM
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Have you done anything to the geometry on the rear axle? Did you put urethane bushings in the rear?...I hope NOT.

If you haven't done anything with the geometry, you probably need to. The rear end with the 4-trailing arm, Watts link setup is the problem. There is a lot of binding that occurs in roll with this setup. This throws your roll rate to infinity and the weight transfer is thru the roof and you overload the outside wheel which then starts to slip....oversteer.

To solve it you will need to go to a 3-link setup. I would suggest going with this: http://www.gforceengineering.net/products.htm

Look at the Tri-Link and the Panhard...dont do one with out the other.

This works well. I have the setup on my CSP autoX car.
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Old 05-17-04, 11:33 PM
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skunks; I've considered that. I raced a stock 84 GSLSE for almost 2 years and had no problem. I also co drove a buddies 82 CSP for about 3 years. No oversteer problem there.
RotaryAXer; the CSP car mentioned above has a panhard rod. When we've swapped cars for fun runs, his feels like its understeering. It may point to my technique. The cost of the combination of panhard and tri link indicates it will be waiting for a while. There are a bunch of things I still need to do before I spend that kind of money.
If there are other (cheap), suggestions I'm open.
Thanks for the suggestions.
Oversteering keeps it interesting, if not fast. ;-)
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Old 05-18-04, 08:15 AM
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Originally posted by f/p79
If there are other (cheap), suggestions I'm open.
Find the softest bushings you can. Typically this means old ones but you won't want to have them so old and falling apart that they aren't doing anything.

Having super soft bushings allows the axle to articulate MORE before the binding starts. It doesn't solve the problem but it helps. It can cause some other problems such as wheel hop on launch but that is minor and can easily be corrected with careful clutch/throttle modulation. Even with the tri-link setup we have old soft bushings in the lower trailing arms. We get wheel hop.

Hope this helps. Good luck.
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Old 05-18-04, 05:11 PM
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Originally posted by f/p79

If there are other (cheap), suggestions I'm open.
Thanks for the suggestions.
Oversteering keeps it interesting, if not fast. ;-)
I have the full gforce suspension and it rocks Jim is Da' man! But for on the cheap, look at my website in the tech section.
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Old 05-18-04, 06:25 PM
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Hey Carl, figured think kinda goes with this thread. I did your trick and it works beautifully!

Previously I had a completely stock 79 rx7 with realy bad snap oversteer. Now the car is gutted. I cut 1/2 a coil in the rear, and 1 full coil in the front. Kept the stock sway bars. Made front turn in spacers (ended up being 7/8" after I milled them smooth). Slotted the upper strut mounts to get more camber. Did your lube/nylock setup in the rear.

Oh my got that car handles so nice. It is almost totaly nutrel. Just a little throtel/break input in the turns and you can make the car do anything you want...very smooth and perdictable. Also if you push it to hard it is amazingly easy to recover.

Just need to get my Holley setup working as well as the suspension and I'll be happy.
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Old 05-18-04, 11:47 PM
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RotaryAXer; I haven't had wheel hop problems, yet.
RX7carl; I've looked at your site before. It may be time to try that. I still have the old bushings in place. I keep thinking I will be done with the car. Once I get it right (?) I can relax. Sure. Thanks to all.
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Old 05-19-04, 01:31 AM
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If you only short the springs in the back, car will tend to oversteer.
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Old 05-19-04, 10:45 PM
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Cruiser; I have yet to corner weight the car. I set the coilovers by measuring the coil/threads. I cut the rear "dead" coils to get the car level. I don't think the front coils should be cut. But, I'm open to input.
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Old 05-20-04, 03:53 PM
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I've been having a similar problem with my '79, also. I have disconnected the rear sway bar, and went back through Ground Control's specs for my car and reset the ride height, and that's gotten about 50% of the problem fixed. The ride height should be 20" in the front and 19 1/2" in the rear, measured from the top of the fender opening to the bottom of the rim (not the ground) this spec is for 13" wheels. I set my ride height with 200 pounds of sandbags in the seat to simulate fat daddy, and I am running 350 inch pound springs front and 175 rear, Tokico Illuminas set at full stiff in the front and setting 3 in the rear. I think PB&J's modification should get a lot of the rest of it out.

I also had to go through a bunch of mods to the front to get sufficient camber, with less than about 3 degrees Victoracers won't bite well. This did involve having to cut the stop of the strut towers for clearance for the camber plates.
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Old 05-20-04, 11:48 PM
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RX744CSP; I don't think I ever saw those figures on the set up. I haven't been there for a while. I will see if that will help. I've already shortened the back springs. (Hint-don't use a hacksaw. Get a cheap grinder/cut off tool from Harbor Freight). I think my springs are the same as yours. Camber isn't a problem. It's set about 2.5 degrees. With the 1'' extended control arms, I have the plate adjustment set at minimum. I was told that when I finally get the slicks, the car will need much less camber. Anyone know about that one? Obviously I have much to learn about chassis set up. I appreciate the help I've received from this list. Thanks.
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Old 05-21-04, 10:52 AM
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I've run up to 4 degrees negative camber on the front with the Toyo RA-1 205/50r13's to make up for the tire rolling on the stock rim (class rules, don't ask). A fellow I've raced with runs about 1.5 degrees negative with 15" slicks and they have amazing bite and fairly even wear.

-Trent
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Old 05-21-04, 02:58 PM
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f/p 79, the figures I gave are on a sheet that came with my Ground Control setup, so they may not be on the website. It gives specific recommendations for different tires. I can fax the sheet to you if you need it, PM me with a fax #. BTW, I'm using standard length control arms in the front.
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Old 05-21-04, 04:14 PM
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You can try a lot of things, but I think you will be happieswt to bite the bullet, and get a tri-link set-up. Susko at G-Force has a great set-up. Trying to really get the rear suspension to work right is like trying to take a turd to prom. You can dress it up, and make the smell go away for a short while, but in the end, it is still a turd.
Seriously, even on stock tires, the rear will bind, even with the bushing mod. now stick better tires, wider as well, and more speed with Solo II type maneuvers, and you will be seeing where you just went. The problem is binding with the upper control arms,and a watts link system that is not designed properly, read equal length link arms. Do away with the watts, upper control arms, put the G-Force Trilink on take the rear bar off, and put the springs from 175-200lb springs. Now go play well with others and have fun
We run this, and have run from CSP with 13" Hoosier DOTs to 12" wide slicks with no transition or retuning of susp to speak of.

Cheers,
Travis
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Old 05-21-04, 04:39 PM
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I had a 79 CSP car that was at the limits of "legal in class". I found that a softer rear spring, combined with no rear sway bar worked very well. I actually wound up using the stock rear springs that had been cut. With the car lowered, I was able to change the rear springs by simply jacking up the rear end. If you still have the stock rear springs, it would be really easy and inexpensive to cut them and pop them in.

Hope this helps, Adam
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Old 05-21-04, 08:11 PM
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Originally posted by T_Racer
You can try a lot of things, but I think you will be happieswt to bite the bullet, and get a tri-link set-up. Susko at G-Force has a great set-up. Trying to really get the rear suspension to work right is like trying to take a turd to prom. You can dress it up, and make the smell go away for a short while, but in the end, it is still a turd.
Seriously, even on stock tires, the rear will bind, even with the bushing mod. now stick better tires, wider as well, and more speed with Solo II type maneuvers, and you will be seeing where you just went. The problem is binding with the upper control arms,and a watts link system that is not designed properly, read equal length link arms. Do away with the watts, upper control arms, put the G-Force Trilink on take the rear bar off, and put the springs from 175-200lb springs. Now go play well with others and have fun
We run this, and have run from CSP with 13" Hoosier DOTs to 12" wide slicks with no transition or retuning of susp to speak of.

Cheers,
Travis
Its not just the length of the upper rods, its their geometry. Its all wrong. Thats why what I wrote up is like I said, a band-aid on the cheap.
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Old 05-24-04, 11:50 PM
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RX744CSP; I went out and tried using those (20",19") figures. I found at the highest point on the threaded sleeve, the most I could get was about 19" front, 18 1/2 rear. I've shortened the rear quite a bit. (duh). I no longer have the old springs. Only so much room to store stuff. I do have a full set (front and rear) TMC replacement springs. No indication of what "weight" the springs are.
They came with a parts car. Could cut these rears down a bit.
T Racer; I will probably get the tri link setup. Going to try to go through Mazda Competition for front tower bar. They suggested an adjustable because the car may have been tweeked earlier in it's life.
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