DaveTurnerMotorsports

Okay, the '89 GTUs is coming back to the shop the end of this week, and the first autocross of the season is this weekend (PCA event on Sat, SCCA event on Sun). Engine is freshened and lightened up a bit by deleting the A/C and going with a very lightweight exhaust.

Suspension is still stock except for the urethane control arm bushings and delrin rear-steering bushing, and cheap-o front and rear strut tower braces until the good ones arrive. I drove it once at a BMWCCA autocross when the engine was bad and stock 180K mile suspension, and it actually felt pretty good-- linear turn-in and cornering and good exit (we later found the LSD had been replaced with a brand-new Mazda unit during a trans rebuild not too long ago).

Since time is running out, I plan on running a used pair of RSR/Racing Beat springs up front (~145lbs) and a custom coilover with a Bilstein shock from a 914-6 and 130lb springs. This closely matches the Racing Beat setup, and we are fabricating the front strut housings to accept a Bilstein P30-0032 sport insert. If/when we get the front built by this weekend, we will probably go ahead and run the 275lb springs up front and 175lbs rear with stock sway bars and end links. We can then add spring or bar as necessary.

Keeping in mind that Mazdaspeed recommends 400lbs front and 275lbs rear for ITS, and most of our local ITS guys run south of there at between 300-375 front and 200-275 rear with inexpensive Eibach or ST sway bars, am I starting at a good point with the above spring rates considering this is for a Street Tire class (>140 treadwear, no "race" tires ie Victoracer/A3S05/V710) that is limited to 225 width and 7.5" wide wheel?

We are running 225/45-16 Hankook RS-2 tires right now on the stock 16x7" GTUs wheels, and will be getting a set of Kosei 16x7.5" later to round out the package.

Thoughts, inputs? This car will still see some street driving, so harshness is of no issue especially if we get the shock tuning down pat (Bilstein is 2 miles up the road).

Thanks!

Black91n/a

I've heard of problems with the Racing beat springs, they're too low and too soft and you'll get rubbing. You can run ground control style coilovers in STS2 AFIK. That would be your best bet, and some good sway bars, camber plates and some rear camber links and get a good alignment. But seriously, don't go crazy at frst, just work on yor drving and get lots of seat time driving, then once you've nearly maxed ot the performance of the car, then add mods slowly and progressively. If you've only done one autocross then I guarantee that you aren't very good yet and there's no point in upgrading if you can't even get the most out of the stock car.

DaveTurnerMotorsports

Multiple National Tour Trophy winner, '04 Solo2 National Championship trophy in STS.......not my first time :-)

Ended up picking up the AWR custom front strut housings to fit the Bilstein race units, still working out spring rates and bar settings. The AWR front bar will not be able to be utilized, as its mounting requires sheetmetal changes/cutting :-(

-JW

carsaregood

james right?

http://www.sdr-scca.com/solo2/schedule/

it says here that the next autox isn't for 2 1/2 weeks! so you still have a bit of time to finish the car. i thought you were going to run it in E stock?

=chris= ( autox newbie in the white, ES fc )

DaveTurnerMotorsports

Chris--

www.Solo2.com puts the first event of the year at this Sat/Sun at California Speedway with Cal Club Region. Our first RallyCross is saturday 1/21 at the Del Mar fairgrounds www.dirtye30.com/sdrally.html . San Diego Region's first event weekend is the 28th/29th.

Too dang busy!

My Bilstein's are delayed a day, may need to spend Saturday wrenching and corner-balancing. Rain due on Sunday, may end up running softer spring rates to start with as I will have no previous practice in the car.

Come on out if you're in SoCal!

carsaregood

dude, the rally cross event looks fun!! do i have to pre-register or do i just show up??

i read the disclaimer about not needing a rally car and that its safe, but i just wanted to double check with you: is the seriously any harder on the car than a regular autox?

RETed

The question is...how serious you wanna get and how much money you willing to spend?
But you already know that by now!

I think you can go stiffer on the spring rates.
Also look into all the delrin bushings that Mazdaspeed (Mazda Comp) offers - this is a race car, right?



-Ted

DaveTurnerMotorsports

RETed-

Considering this is a true street-tire class with wheel/tire size limitations, and we see surfaces ranging from slick asphalt to bumpy concrete, should I really be going up in spring rate? Even Tony at AWR shied away down the range from the standard 400/275 that the ITS guys run, though it was not uncommon to run very high spring rates in our other racecars. I've never set up an FC for autocrossing on street tires (did some testing with Steve O'Blenes and his BP car a few years back, even he was running 400/275 for two years before going to the Penske's and cockpit-adjustable sway bars), so I begin here with you guys.

Also, it's going to be a little bit wet and cold on Sunday.

Soooo.....275/175 too soft? 400/275 too stiff? What would you recommend as a starting point then, given that I may tune furthe depending on my driving style or lack of it?

I have a pair of 2.5x8x400# springs and several pairs of the same in 150, 175, 200, and 225 as well as 450, 500, and 550 on the shelf right now. I'm worried that the rear will need at least a 10" spring, but the Bilsteins have locating rings and a 7" coilover.....it's tough playing guessing games when the car is not in my shop :-(

RETed

I think something in the ~300F / ~200R range should be a good starting point.
Personally, I would go with Koni yellows; if you're serious, go double-adjustable later.
In autocross, you want a little more weight transfer, especially when you're first starting out, so the softer rates will help with that.

I think the 400F / 275R combo is a little bit too stiff, unless you're running on very smooth surfaces.
I run that combo on the street, so I'm very familiar what it can and cannot do.
On a higher speed road racing track, this is a good combo, but for autocross I think it's overkill.


-Ted

DamonB

Weight transfer is not a function of spring rate. Weight transfer is a function of CG height along with track and wheelbase dimensions. Weight transfer is the same no matter what springs are on the car.

RETed

True...but...
What we perceive[sp?] as "weight transfer" is subjective.
Look at the extremes...
With ultra stiff springs, things happen in a jiffy.
With softer (i.e. stock) springs, the chassis tends to react a lot slower.
The slower the transition from stick to slide might be beneficial to beginners.


-Ted

Richter12x2

iTrader: (1)

Gotta disagree - my 2nd gen RX7 is down with a blown seal for the last race of the season I raced my wife's 12 year old Mustang with original springs, and the springs in the back are so weak that if you give it gas during a corner (which I can do in the rx7 to bring the rear around) it unloads the front tires (and these are 245's!) to the point that the car doesn't steer. With stiffer springs it doesn't unload the front tires as much, because the spring rate is counteracting the weight shift.

Richter12x2

iTrader: (1)

Oh, but after my engine rebuild, I'm going to be going to the recommended ERS 400/275 setup, and I'm thinking about the KYB AGX's - any thoughts on these one way or the other for autocross/racing use? I've heard about the Koni's, Tokicos, and GABs, but I've got a good deal lined up on the AGX's at $450/set, they're all externally 2-way adjustable, and the adjustments are on the sides. That's the plan I'm going with as soon as time and money permit. My cousin-in-law that got me started had a top 10 STS Civic car at the Solo2 Nationals last year, and he's running 550lb springs in the back, so I don't think 400 in the front would be too much for Autocross so much. But if you have to drive it more than 30 miles to the track, I bet you'll regret it. Besides, springs are the least expensive part of that setup, with Eibach ERS's running about $55 per.

DaveTurnerMotorsports

RETed--

With those spring rates that you run on the street, what sway bars are you running? Has anyone calculated out the rate for the stock GTUs bar versus an ST or Eibach 28mm unit? Do you run the rear bar as well, or just the factory piece?

-JW

DamonB

No it's not. Weight transfer is a clearly defined term in regards to handling.

Then you are not talking about weight transfer, you are talking about response. Two different things. Weight transfer will be the same with ultra stiff or with softer springs.

The same weight shift happens regardless of the spring rate. You could weld solid steel bars on in place of your springs and weight transfer would still be exactly the same. Changing spring rates makes cars handle differently, it doesn't change weight transfer in any way. Ever. Karts have no suspension at all and they still experience weight transfer.

Spring rate does not enter the equation:

longitudunal weight transfer = weight x cg height / wheelbase x g

lateral weight transfer = weight x cg height / wheel track x g

Weight transfer happens because the CG of the car is above the ground while the contact patch of the tires (where all reactions through the chassis take place) is on the ground. How much weight will transfer from one tire to another is a function of CG height, track width, wheelbase and grip. That's it.

Weight transfer is bad because it causes the tires to work less efficiently. To minimize weight transfer you try to get the CG as low as possible. If you could get the CG to ground level you'd have no weight transfer at all, but that's impossible.

The Physics of Racing Part 1: Weight transfer

Richter12x2

iTrader: (1)

Keep us updated though, I've just started autocrossing this last year so I've got a ways to go, and I'd definitely be interested to see the results of a seasoned driver in a well-equipped (trying not to use the word 'prepared') FC in STS2. I moved up to running about 4th place in the Texas Region, but I'm just running an essentially stock '87 on 215/45 r17 Kumho Ecsta 711's with a 3" exhaust and a cone filter. I feel like I did really well for my first year though, especially since I was the highest ranked car that wasn't trailered in.

Richter12x2

iTrader: (1)

Okay, then in the interests of technical accuracy, I'll clarify my position. I'm looking at stiffer springs to reduce the effect that weight transfer has on the traction of my car, not to reduce the weight transfer itself. Does that appease your sensibilities? Because while I can't control the amount of weight that shifts to the rear or front or sides of my car, stiffer springs will keep that weight from compressing as much, which will reduce the body roll that removes traction from the wheels that the weight is shifting away from. i.e. on acceleration, the stiffer springs in the front pushing down harder, keeping more contact patch on the ground, works with the stiffer springs in the back that are pushing UP harder, reducing the pitch of my body, reducing the body roll that comes as an effect of the weight transfer, yeah? So while the amount of weight that is transferring will remain the same, the moment weight felt by the back tires will be less and the moment weight of the front tires will be more?

While the technical aspects and terminology of the physics affecting my car are interesting, I'm more concerned with the practical effects, which involves that with stiffer springs, my car will stay flatter, roll less, take a set faster, and feel more predictable than softer springs. I guess the root of all this is that I'm glad there are people in the world who can explain the things that I know to be true and feel instantly in the technically correct terminology and mathematical equations that I don't have the time or inclination to learn. I'm not knocking it, these are the people who make incredibly accurate racing simulators like Gran Turismo and Enthusia. At the same time, I've never felt the urge to say "my rapid increase of effective torque incurred during the high lateral G's accrued during the peak of my yaw moment has exceeded the terminal traction ratio of my anterior contact patches" when I could just say "The back end gets a little loose around corners"

Josh

DamonB

Be careful of comparing spring rates between two different cars. How the spring is mounted to the suspension comes into play as well. Essentially different cars with different suspensions have different leverage on the spring. A 550 lb spring on a Civic will not be the same as a 550 pound spring on an FC; their suspensions are completely different.

The stiffer springs do not reduce the effect of the weight transfer, they merely make the car stiffer. This will make changes to the response and balance of the car only.

How many Texas Region events did you run?

Richter12x2

iTrader: (1)

Oh wow, just noticed you're from Dallas, too. I only ran in 5 because I got a late start last year and I missed the last one because my RX7 was (and is) still out. I know he needs a stiffer spring in the back of an FF car to make the car rotate faster since they have a tendency to understeer, which stands to reason you'd want the stiffer one in front of the car to reduce oversteer in a FR car. The power understeer effect I mentioned earlier was during the "Hurricane Relief" event with Wayne in the car. I came into the last turn a bit hot, and bumped the gas to get a little power-over steer like I was used to in the RX7, but as soon as I accelerated, the car just went straight forward. Had a nice clean run and just plowed over that last cone in the corner because of that. If you were at that event, that was the time I dragged that cone all the way to the finish line. The cone guy said "Well, at least we know you got one cone!" and I said "Nah, it was there when I started!"

Richter12x2

iTrader: (1)

Oh yeah, just looked at your profile! I've seen you race before. You probably didn't pay any attention, mine's the little charcoal gray second gen. I ran in CSP exactly once, but I knew I couldn't keep up with the Miata squad. I fit much better in with the STS2 crowd, but as was proven everytime Phil trailered in his fully equipped STS2 CRX, my little street car just couldn't keep up with the serious race cars (at least not with me driving it) - now I picked up a Neon for a dependable street car I can start doing what I need to do to the RX7 to make it more competitive. Well, once the engine is rebuilt.

DamonB

Springs do not push down on tires. If they did everyone would run 3000 pound springs and have ultimate grip. Only the weight of the car can push down on the tires and that weight doesn't change if springs are soft or hard.

The weight of the car determines how much mass there is pushing down on the tires and you can't alter that mass by changing anything in the spring rates.

The springs on a car support the chassis and control movements of the chassis in response to reactions through the tires. The springs only support the chassis, they in no way press down on the tires.

The amount of weight that is transferring IS the amount of weight the tire(s) will feel. That's all there is. Springs cannot move weight around on a car.

DamonB

Don't worry about it; just have fun. We all suck when we start. When I started autoxing in my FD my raw times were slower than the 95 hp Civics in H Stock Wayne and Phil are excellent people.

DaveTurnerMotorsports

We used to run 400-450 in the front of the STS Honda's depending on which sway bar was used (stock, HF, or none) along with 550-700lbs in the rear depending on which tire was used and the track surface...this was with the OTS Koni race single-adjustables.

We're running the Bilsteins this year because of their excellent local support and service (they are here in San Diego), and on a road course they tend to not heat up as much across a period of time as the Koni's. I've run nearly every shock on a ton of different autocross cars (this is my 14th, hehe), and I've found that if I have to adjust much of anything beyond tire pressure once the car is properly set up, unless the course is "poor", then usually changing my corner entry will have a much more profound and beneficial effect than cranking an adjustment **** on a shock. This is just for my own personal driving style. I think that across the year with the STS Honda, we may have used the little Koni **** twice...once to try something, and then immediately to put it right back :-)

Still looking for springs for this weekend, noone seems to have a pair of 2.5x8x300's right now, and I'm out of stock.

-JW

DamonB

I've always been more of a tinkerer. I had the car working well but now I have little changes I make for different surfaces, type of course, weather etc. I could drive through anything with what I had but I can go faster by tweaking the car for that day at that event. Maybe the Hondas just don't need it. I don't see our fast STS Civics tweaking shocks much. Springs and pressures, yes.

Richter12x2

iTrader: (1)

yeah, he may hate that I said this, but Wayne's got a SAFC II in his Civic and he says he's never touched it. Same thing with his adjustable koni's. Seems like he's in first and second every time though. He's the one that told me that if you go for adjustables, try to get the two way adjustables. I'll probably leave them alone for the most part once I've got them set the way I like, but I've still got to get them set the way I like!