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How competitive FC in STS2?

Old 05-01-07, 12:20 AM
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How competitive FC in STS2?

Does anybody have any experience of how competitive a well prepared FC would be in STS2, compared to comparably prepared Miata?

I've driven it once at an autocross and was a couple seconds behind other drivers of my skill level.
'89 GTUs, AC, glass sunroof, AGX, Tanabe (168/140), Azenis RT-615 215/45-16 on stock 17 lb. 16x7 wheels. I had no camber adjusters on it so camber was about .7/2.4 f/r. Needless to say it had understeer.
I just got AWR rear camber adjusters, Tein front pillow-ball mounts, and poly front control arm bushings. This should take care of the camber problems, but I will still need stiffer springs (Ground Control), sways, and probably better shocks.

I know, it's mostly driver, but the driver will be the same now matter what I drive.
My guess is that a moderately prepped FC will be an average of 1 second off the pace of a comparably prepared Miata.
Does anyone out there have much experience with autocrossing these things against Miatas, in a class like this? I've been searching and can't find too much. What do you think? I know it will depend on the course, but on average. Most of our lots are asphalt.

If you like, email or PM me. I want your opinions!

Thanks,
Jim
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Old 05-01-07, 12:55 PM
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I was thinking about build an STS2 car, but I think I'm going to be build an SP one instead, the STS class just feels a little too limited for competitiveness. No engine mods and cat on a rotary doesn't feel good to me. I just read the rules today, and am not sure if you can even use coilovers in STS class, I think you can use them in SP class.
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Old 05-01-07, 02:07 PM
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A guy named James Wilson ran one well in CA last year before he sold it.
His forum name is DaveTurnerMotorsports. You can search for all his posts. Here is one on the suspension issue:

https://www.rx7club.com/race-car-tech-103/fc-autocross-suspension-setup-sts2-498143/

I wanted to build one out of my '87 but I don't feel like swapping to an open dif instead of my clutch type dif. If you have a viscous dif car it would be a good class.


Here is another good tread:
https://www.rx7club.com/race-car-tech-103/solo2-tour-prosolos-approaching-512165/

Last edited by finky; 05-01-07 at 02:15 PM.
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Old 05-01-07, 03:32 PM
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Miata will have a large advantage just because they are much lighter. Top cars are sub 2000 pounds.
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Old 05-01-07, 08:42 PM
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The biggest disadvantage is that you can't run a larger tire than the Miatas and CRXs can. STS2 limits tire width to 225, which is barely adequate for the heavier FC. I'm personally running CSP, but that's mostly because of a few other mods I've done that aren't STS2-legal (cat, etc.). I'm currently drooling over the new 275/35-15 Hoosier A6

IIRC the SFR runs a street-tire index class, don't they? You could prep to the less restrictive CSP rules and still run on street tires if they do.

-chris
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Old 05-01-07, 11:48 PM
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Yes, those were good threads by the guy from Dave Turner Motorsports. I didn't know his name - thanks! I just looked for his race results and found a few in the first few races of 06. He was a couple seconds out of first, but with consistant times. I'd like to know what he thinks. I think he and his competition are good drivers.

I agree with what you guys are saying about the weight and being limited to 225 tire width. I'm just trying to see if others have tried it and have a good guess on exactly how far back they are.

Yes, SFR does have a street tire version of CSP. That's what class my '95 Miata would be in because of it's torsen diff. I'm co-driving a Miata in STS2 now.

I'll get those camber adjusters in it and see how it does with the Tenabe springs and stock bars.
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Old 05-02-07, 12:08 AM
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I'm thinking about building an ITS car for CSP instead. Since CSP doesn't allow porting or some weight savings mods, I think the ITS route is the way to go, since you can pretty much strip out your whole car, save a couple of things. No induction modifications are allowed in ITS, but that's not such a big deal, as long as you can use the standalone and full exhaust to your advantage. I thought there were minimum weights for each class, I don't know how you could get 2200 for SCCA Solo.

I had a long chat with the rules guy from SCCA today, I'll post all my questions and answers tomorrow, but I do know that rear camber adjusters are not legal in SP, though I am curious to see if one of the rules in STS allows for rear camber adjusters. Not sure about ITS either. The problem with ITS is that they won't let you use any larger than a 15 x 7 rim, and you have to keep a certain wheelbase, so effectively you're limited to 225/50/15 or 225/45/15 tires.
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Old 05-02-07, 09:33 AM
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Suspension is open in ITS. An adjustable rear camber bar is allowed and pretty much considered a must.

-b
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Old 05-02-07, 11:19 AM
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I wouldn't say it's free, just more liberal than the Solo classes. I have the rules in front of me, and it doesn't specifically allow the use of camber rods or links. It only has an allowance for eccentric bushings. It says "Independent rear suspension mountaing holes may be slotted or reinforced for purposes of camber and/or toe adjustment."

Talking to the rules guys, they said "If it doesn't say you can, then you can't."

I'll e-mail him specifically and see what they say about using rear camber adjusters. (Links or Rod)
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Old 05-02-07, 05:59 PM
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If you prep an FC to SCCA EP Roadracing rules you can run in E Prepared auto X class. Just a heads up if you wanted to go that route.
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Old 05-02-07, 06:37 PM
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Originally Posted by wrankin
Suspension is open in ITS. An adjustable rear camber bar is allowed and pretty much considered a must.

-b

It's really not allow but everyone runs them.
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Old 05-02-07, 11:41 PM
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I was wrong above, DaveTurnerMotorsports actually did better then I thought.
I read all of the threads posted above again (I'd read them months ago). His co-driver won the local National Tour event, and he won the Pro-Solo. In his local events, it looks like he was against 2 national champs in Miatas.

I'd love to hear his opinions, or others - but we do have his setup.

That's probably right about the rear camber adjusters. I'll read up on it.

The ITS in CSP is very interesting. I'll watch for that.

Thanks all!
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Old 11-26-07, 12:33 AM
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I think it's only using the outsides of the front tires in corners because it's leaning too much.
Last autox on concrete I finished with 39 lbs. in the front tires and the center was cooler than the sides.
I think what's happening is something like: the car is rolling say 5 degrees, camber is -3, end up with 2 degrees positive camber.

When driving it's hard to rotate the rear. I think the problem is not enough grip in the front.

Current setup:
375/300 springs,
KYB AGX shocks, Tein camber plates at 3 degrees negative (max), with some toe out.
RB tubular front bar, stock sport 14 mm rear bar.
Ride height ~ 13.5" F/R (wheel center to fender brim).
Falken Azenis RT-615 215/45-16

I'm going to try 550/400 rates next (I have 450 & 550 in 6" and 325 & in 7"). I know this should be too much for AGX, but I can see what happens. I think I need to cut the rolling way down.
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Old 11-26-07, 09:22 AM
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You might want to consider switching to independent adjustable shocks if you have the money (Koni, Penske, Ohlins, JRZ, Moton, etc.)
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Old 11-26-07, 06:58 PM
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I used to autocross quite a bit in STS2. I was always 2-3 secs off the Miatas in San Diego. but these guys are really good. The class is ruled by Miatas and soon the Solstice will invade. But if you want to have fun I here you can get the Miata guys to buy the beer after an event! Seriously, what do you feel happening with the car? iIs it understeer or oversteer? Before you start swapping springs (drastic set up change) keep in mind how they will affect the car and what you are trying to accomplish with your changes. Personally I'd leave the rear alone, stiffen up the front, and get as much neg castor as you can get your hands on even if it isn't legal (I did't say that out loud did I ). I can't vouch for spring rates on AGX s but I can tell you that my experience with Bilstiens is that when you get anything above 350 Lb spring rates in the rear it gets very tail happy. I ran 8"-450# f/ 10"- 300#r A really heavy speedway bar up front and a stock T2 unit in the rear. This is recommended as a starting point by AWR and a few EP cars that I know of. It was a pretty neutral set up with 225 Avenis. Probably a stupid question: have your DSS bushings been replaced with RB units? What are you running for bushings in your front control arms? if these are stock change them to at least Urethane. I've checked several FCs for binding here, they all bind badly with the stock rubber and will bind up here in several mos with urethane unless they are greased often. To much deflection as well. I don't think AWR stuff is legal in STS2 but if metal bushings are legal you'll need the AWR stuff to be competitive. I'm prety sure Chris (Dave Turner MS now JMC) ran these in the front. If you aren't kickin *** and taking names in STS2 you won't be scruntinized. Personally I like CSP and E Prepared better for a FC. We like wider tires. Good luck hope this helps
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Old 11-27-07, 01:06 AM
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The speedway bar sounds good. $465 at awrracing.com is expensive for me; then $275 at iscracing.net with no picture.
I think I'll start with 450s with in front, lowered more, set very close to foam bumpstops.

I'll take your advice on rear spring rates and leave the 300s in for now.

I got urethane bushings for the front from mazdamotorsports but haven't put them in yet. I will replace the DTSS bushings at some point.
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Old 11-27-07, 08:49 AM
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Well since this discussion got re-started, I figure that I might as well ask my followup question about the rear adjustable camber links in SCCA Improved Touring. Chris commented that:

Originally Posted by C. Ludwig View Post
It's really not allowed but everyone runs them.
Interesting, I had always assumed that they were legal.

I went back through my 2007 GCR and while this may be a stretch, I think that it could be argued that they are legal by a combination of 9.1.3.d.6, which allows for replacement of bushings by spherical bearings, and 9.1.3.d.2, which allows for the adjustment of camber with offset bushings.

Not a big deal either way. Like you said, everyone already runs them and their use is in keeping with the other allowed suspension modifications.

-bill
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Old 11-27-07, 10:31 AM
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Yea, doing legal function with a potentially illegal method. To me those would be more legal than the center adjustment bar because that changes the inner pivot points of the arms, whereas the individual ones don't. If you have bushings and not spherical bearings in your trailing arms then you should be careful when using individual adjusters though, because if you adjust those very much it'll cause binding in the trailing arm bushings. This will be worse or potentially damaging if you have harder bushings like polyurethane or delrin.
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Old 12-14-07, 12:05 AM
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The car is much better now.
I changed the spring rates from 375/300 to 450/325; and from Tein camber plates to AWR camber/caster plates.

I'm not understeering so much - it seems pretty neutral; not rolling as much - would like to decrease it more; not wearing the front tires on the outsides anymore - now seem to be evenly warm.

The Tein camber plates come with a big spacer to be used underneath; that allowed a minimum 13.5 front ride height with the 6" 375 springs - that would be worse with the 6" 450s. With the AWR camber camber plates and 6" 450s, the
ride height is ~13.5" maximum. The AWR plates are made for Koni & Bilstein, but I got them to fit by grinding down the shock rod so the upper spring mount sits around 1" lower. This allows the shock rod to go up inside the mount far enough to get the nut on it.

I ran with a ride height of about 12.5/13.25. For bumpstops I'm using about 1" of hard rubber cut from the originals, plus the firm linear 1.5" foam bumpstops from Ground Control. I've only done rough measurements so far, but it should touch the bumpstops at about 12", and have them fully compressed at around 10". I wanted it to get into the foam bumpstops to help with the spring rates. I stood on one and it seemed that 200 lbs compressed the bumpstop about 1". So far it seems like the AGX is controlling this fine. My sway bar is not so easy to move, so I'm sure that helps. Bumpstops don't need much of a shock because they don't rebound much. I want to go to 550 springs (when I get them off my Miata) in front, and use a shorter harder bumpstop, but the AGXs may not handle this too well.

Current setup now:
450/325 springs,
KYB AGX shocks, AWR camber/caster plates at 3 degrees negative, max caster, 1/8-1/4 front toe out.
RB tubular front bar, stock sport 14 mm rear bar.
Ride height ~ 12.5/13.25" F/R (wheel center to fender brim).
Falken Azenis RT-615 215/45-16; pressures 40/37

For future I'm thinking of changing to:
550/400 springs, remove the rear bar, get helper springs for the rear so the springs don't come loose and can hopefully keep some pressure on the inside wheel.

More suggestions are welcome! The speedway bar was a good one, and I'll eventually get to bushings. The fronts move freely and don't seem to have any play.
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Old 12-14-07, 06:00 AM
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I would suggest a higher performance damper like the Koni Yellow - They handle the spring rate better than KYB, Tokico, etc.
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Old 12-14-07, 06:43 AM
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Yeah. Konis are the way to go to control spring rates that high. I don't know that I would go much over 500lbs. on the springs on street tires(concrete-yes, blacktop-no). It is totally dependent on the surface you run on.
Also look at the Bridgestones and the Yokahamas in a 17" size(what did the 89 sports have for a dif gear? Do you have 4.33s to run a big rim in the high revs?). They have proven faster than the Falkens. Also, there are a new crop of ST legal tires coming out this year that should prove to be very fast(kumho, dunlop).
Get 225s and 7.5" wide rims. You need all the tire you can get to run with the Miatas and CRXs.

Last edited by finky; 12-14-07 at 06:57 AM.
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Old 12-14-07, 09:27 AM
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If you're going with 550/400, I would say buy some Koni Race Dampers that have individual compression and rebound adjustability. I believe that's the most sophisticated suspension you can run in STS2. (Dampers with two adjustments, one for compression, one for rebound, no remote reservoirs)

I would say get 225's on a 7.5 in rim in the smallest aspect ratio and rim size you can get. You can always use an extra boost in acceleration with tire grip to boot.

Speaking of which, what's a good 15 x 7.5 rim?
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Old 12-14-07, 01:49 PM
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http://www.18racing.com/wheel_slipstream.html

You'll need a spacer, but it's a hell of a deal, and they're decently light. There's the new Toyo R1R that'll be coming out in a 225/45/15 in the spring. Apparently they designed it to be the tire to beat in ST class competition.

From what I've heard you're already at the limit of what an AGX can handle. Going to the 500/400 you'd probably need to have Koni Yellows revalved to handle it.
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Old 12-14-07, 02:04 PM
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booooo for spacers.......

I wonder what would be ideal......225/45's on 15 x 7.5, +30? Optimal balance between transitional handling and ultimate grip?
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Old 12-14-07, 04:12 PM
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The problem of the 15" rims is that all the good tires at the moment are 16"+ and you need to go 17" to get a 225.
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