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1st gen suspension setup.

Old 10-09-03, 02:43 PM
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1st gen suspension setup.

Alright, I know there are some race guys in here who will have more experianced answers with this...

Right now I run GC coil overs on 350# springs up front, Illuminas on all corners.

I'm going to be switching to the RB 1 1/8" sway bar up front and different spring to bring the rear down a bit.

As it stands now I LOVE the way it handles. Very very neutral with a slight tendancy to oversteer. I'd like to keep that same balance but flatten out the cornering and attempt to get a slight bit higher overal lateral g's.

Ok, now that all of that has been said... What's the ideal spring rate for the rear?

I know GC does 125/150/175/200
http://www.ground-control.com/gcrx7cat.htm

but what I'm really eyeing are the ISC adjustabel setup. 150 or 125lbs?
http://iscracing.net/suspension_2.htm

Suggestions? Inputs? thoughts?
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Old 10-09-03, 02:56 PM
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I use GC 350 up front and ISC 150 threaded spring perches in the rear with a custom tri-link that mounts on top of the pumpkin and goes thru the floor and mounts to an adjustable height bracket welded to the crossmember behind the seats. My GC panhard rod works well but GForce makes a better one.

Handles like a dream. Very controllable and just a hair of oversteer when exiting a turn. I did have 125 in the rear but it understeered thru the turn especially on corner exit and I was scrubbing off speed.

This is for track hot lapping, not setup for auto-x. The general rule with 1st gens is to have the front springs a little more than 2x the rate of the rear springs. A friend raced ITA and had 400 front 200 rear and did *very* well.

Some of the florida ITA guys don't use tri-link in the rear and instead put 220lb rear springs in there with the idea the rear won't compress enough to bind and exacerbate the oversteer issue. I tried that but it still oversteered because rear springs were too stiff. Had to wait too long before applying throttle on corner exit.

I think with mabye 500lb front springs it could help but DOT-R's might not be able to handle that much front spring on 1st gen.
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Old 10-09-03, 03:06 PM
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yeah, I'm still currently running the stock watts linkage in the rear.. That's kinda been why I've stuck with my "half assed" race suspension, but for what I've spent I can beat more than enough cars...

but I'm to the point where I think I have driven enough that I can make use of those extra little bits here & there..

but anyway...

If I stiffen up the front w/ the bar I knwo I shoud stiffen the rear as well, but I want to keep the balance.. Sounds like ISC 150lbs would keep me about where I want.. Hopefully I can use the adjustable feature enough to minimize the binding on the rear, but still get the appropriate stiffening...
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Old 10-09-03, 03:44 PM
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I guess I should add...

car gets used on the street, the track and autoX. I'd like to aim for a combination of track/AutoX handeling...

(keeping in mind that most of our autoXs here are high 3rd gear and ~1,5mile 80+sec courses)
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Old 10-15-03, 04:54 PM
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bump

bar ordered (Mazdacomp is offering free shipping )

rear setup opinions welcome..
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Old 10-15-03, 05:05 PM
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Originally posted by rx7gslse
bump

rear setup opinions welcome..
Tub it and put some 12 inch ET streets out back.
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Old 10-15-03, 09:55 PM
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I use a 1 1/8" non adjustable front sway bar up with poly bushing front and no rear bar. Works very well with the spring rates I quoted above.

The adjustability feature of the ISC threaded spring perches is just used to raise or lower the rear of the car very easily. It wouldn't minimize the binding unless you jacked the rear up very high to a point where the suspension won't compress down to the point where it starts to bind. But doing that creates other problems with rear center of gravity, etc..

I think you're ready for a heim-jointed panhard rod. Lowers the rear roll center significantly; rear end doesn't step out as much. And if you wanted more oversteer just cut spring to raise spring rate K.
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Old 10-16-03, 10:34 AM
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Originally posted by DriveFast7
The adjustability feature of the ISC threaded spring perches is just used to raise or lower the rear of the car very easily. It wouldn't minimize the binding unless you jacked the rear up very high to a point where the suspension won't compress down to the point where it starts to bind. But doing that creates other problems with rear center of gravity, etc..

I think you're ready for a heim-jointed panhard rod. Lowers the rear roll center significantly; rear end doesn't step out as much. And if you wanted more oversteer just cut spring to raise spring rate K.
yeah, I know the adjustability is just for ride height, but I was under the impression that lowering the suspension is what led to the binding in the 1st place... the goal was to get a stiffer spring rate, and be able to keep the car at a height where binding could be avoided until a later date when a less streetable suspension setup is installed in the rear...

A panhard woudl be nifty, but how does that do on the street?
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Old 10-16-03, 10:35 AM
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Originally posted by Umrswimr
Tub it and put some 12 inch ET streets out back.
Dave, you're not helping
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Old 10-16-03, 11:33 AM
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dont forget to do something with the brakes... i know they get hot...even autocrossing...


want a lower control arm for your mantle?
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Old 10-17-03, 09:52 AM
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I am by no means a Jim Susko of suspension . But here is my .02. Me and a buddy currently run a 81 that he has had for about 6 years. Up until about two year ago, the car was a competitive CSP car. We have moved to AP, but I digress.
In CSP, he ran the G-Force tri-link with panhard. The front setup is GC coilovers, Advanced Design shocks, and ST sway bar. The rear is 150 Eibach with Tokikos. Because you must keep the lower and upper links intact for CSP, we took the upper links and removed the bushings. filled the attatchment point with foam to prevent the clanking of the metal to metal and worked beautifully. Also, no rear sway bar. Very neutral, slight tendancy to oversteer if you get real aggresive, but very controllable and very quick. On Hoosier DOTs, BTW.
As I understand it, the binding and snap oversteer is a result of the upper links binding along with the watts getting the rear all contorted, then WHAM, infinite rear roll stiffness and you are looking at where you just came from. I am not sure how serious of a setup you are wanting RX7Gslse, but I love the panhard setup. I would do this to my street car in a second. I am a werido anyway, and have gotten much grief for my car being obnoxious, too low, too stiff, too noisy. Whatever, I want to know what is happening with the car. I also hate the vagueness of stock setup with stock bushings. I like to drive "somewhat" fast on the street or backroads, and in my opinion a sloppy suspension will get you in more trouble, ie tanks slappers, than fast with a good setup will.
I dont know if this makes any sense, but hope this helps and feel free to probe for any further questions. Good luck.


Travis
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Old 10-17-03, 02:02 PM
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excellent.. That's for the info..

150# ordered, along w/ ISC racing adjusters.. I'm going to look into Rx7Carl's Nylock setup for the time being...

I need to see if someone here local w/ a tri-link/panhard will gimme a test ride to see how they do before I drop that $$$ just yet...

PS - also finally got around to ordering the "bible" (aka Susko's book) so maybe I won't ahev to ask so many stupid ?s.

Last edited by rx7gslse; 10-17-03 at 02:12 PM.
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Old 10-17-03, 02:42 PM
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Originally posted by Umrswimr
Tub it and put some 12 inch ET streets out back.
Dave, the guy's car makes what; 115 hp? Half a 12 inch tire would be too much! Or did you mean diameter?

As for T_Racer's commnet on the upper links: take note. There are lots of race classes that make you retain stock links sometimes, but they don't say you can't add additional ones or what your bushings have to be made from. Lots of guys like their bushings made from air because they have panhards, 3 links, etc
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Old 10-17-03, 02:45 PM
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Originally posted by DamonB
Dave, the guy's car makes what; 115 hp? Half a 12 inch tire would be too much! Or did you mean diameter?

As for T_Racer's commnet on the upper links: take note. There are lots of race classes that make you retain stock links sometimes, but they don't say you can't add additional ones or what your bushings have to be made from. Lots of guys like their bushings made from air because they have panhards, 3 links, etc
118 thank you!!

Yeah, I need to do a bit more reaseach into class rules, and the desired rear setup.. Hopefully I'll have the time & ability to make the changes I want to over the winter and come back with new toys for next year.. After the EVO school I think I now know enough about how to drive the car that I will be able to take advantage of the changes. (a 2second cone ruins the advantage of $$$ spent on car parts )
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Old 10-18-03, 09:16 AM
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Damon, the only reason for mentioning the foam was to eliminate the clanking. I am doing the same thing as using "air" bushings. The foam that I used was extremely soft, no kind of support, out of an upholstry shop I believe. I only used the foam to eliminate some of the clanking. With the full three link setup, all spherical bearings and tilton twin disk clutch, any poking along the paddock and up to the start line would make the whole rear end sound like it was coming apart until it was under load. Under load it was fine, but idling or light throttle and people would look at me and ask what was wrong in the rear. Helped me because some thought the car was broke, so they thought they had it easy.
Anyway, with the upper links on and foam, you could grab the UL and move them about 2 " each way. No way for them to bind.

Cheers
Travis

P.S. Damon, I have not been here that long, but looking around I see you are from TX, and race with Eric and Beth. They were still in Jacksonville, FL when I first got into racing. Great couple of people. Really helpful, and both are great drivers. Sorry to see them leave. BTW, does Eric ever bring his kart out to events, or just use the kart at kart tracks?
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