TeamRX8

iTrader: (25)

It seemed ironic that you claimed more grip yet posted a picture indicating the opposite

BRODA

iTrader: (7)

Looking for some used Toyo R1R's . Please PM me if you have a set available. Thx.

TeamRX8

iTrader: (25)

Got a 1/2+ tread depth set of 255/40-17 BFG Rivals ...

Clark18

iTrader: (2)

I have some nice sets of Hoosier A6s, A7s and R7s available in the 245/40/17 flavor if y'all can run those--I don't know autocross rules.

Tofu*Monster

Ran the San Diego region last Sunday. Loving the addition of adjustable rear bar. Finished 2nd in class, so it was a good weekend.

Nathan Atkins

that looked like a pretty nice course! Lots of grip available, our lot is covered in this slippery sealant so you can only develop so much.

This was my first event with the new springs on (10kf/7kr) and still with the factory shims on the Bilstein HD's, I still need to get used to it a bit but I think there is more potential there now, if I have time before my next event I want to get them dynod and swap out shims to get me that magic 65% of critical damping.

fourwhls

A little late, but.....

Congrats to Ken & Allen at the Wilmington Champ Tour. You guys were getting it done. Simmons was on fire that weekend and we were all chasing him. It was nice meeting you two.

Best of luck to all of you heading out to Lincoln. A heat dedicated to STX is just too cool. I wont be joining you all this year, but next year is on the calendar as of right now.

Kennetht638

iTrader: (2)

Thanks Shawn! We're finally getting the car setup where we want it so hopefully our luck holds out for Nationals. It's too bad you're not going to make it out to Lincoln, it was nice meeting you and it was really cool seeing lots of RX-8s in grid at Wilmington!

Simmons-Racing

iTrader: (1)

Allen definetly had me worried about him jumping ahead of me on Sunday.
Nice driving by all 3 of you guys.


See you guys in Lincoln next week.


Simmons

ion_four

iTrader: (1)

I'm curious if there is anyone (competitive and willing to disclose their setup, har har) running "soft" springs in STX? A wink and a nod would be sufficient.

Here's why I ask: I think that most off-the-shelf (especially cheaper) coil over kits seem to include springs that are of a QUITE high rate (3-5 times stock), regardless of how "sophisticated" the suspension is of a given vehicle, in regard to dynamic alignment. I'm talking about all cars, not just the RX-8. Is this just conventional wisdom, passed down from less sophisticated suspensions of the past, that stiffer is better? Or is a ~2Hz ride frequency THAT desirable?

If one looks at various manufacturers, they may offer coilover packages for a variety of cars and all springs are within the 8/6k to 10/9k region, regardless of MacPherson strut, multi-link, or double-wishbone geometry. I understand *excessive chassis movement* from lower spring rates is not desirable, but our suspension is meant to have some travel, no? Stiffer and stiffer springs and thicker and thicker sway bars do not a faster car make, as we don't compete on a sheet of glass. My local venue is pretty **** poor and might be mistaken for a rallycross course, instead of autocross, but maybe that's a personal problem.

My suspension is currently stock, but I'm planning on ONLY doubling the spring rates, valving shocks accordingly and maybe increasing sway bar stiffness by 25-50%. Heresy? Perhaps this is more of a suspension forum question...So...feel free to not address the details and just let me know if anyone fast is running springs only 2-3 times as stiff as stock, front and rear. lol

Kennetht638

iTrader: (2)

Once you say that weight transfer from lower spring rates is not desirable, you show that you're not understanding what's going on. My intent here isn't to make you feel bad that you don't get it, but you should go back and review what you think you know about suspension before you try to reinvent the wheel. You're right that stiffer is not always better, but there is definitely an optimal range of spring rates and roll stiffness depending on input frequencies and tire stiffness (among many other things). Unfortunately, most autocrossers don't have the resources to model these kinds of interactions but the state of competition means that many setup permutations have been tried. Of course this doesn't mean that the current state of the art is ideal and you are definitely free to try new things, but this depends on what your goals are. Do you want to go fast or do you want to fiddle with things? Are you already an ace driver looking for an edge on your competition?

And for what it's worth, a site that's local to me is notoriously rough as well and my spring rates at 550F/350R work extremely well there.

ion_four

iTrader: (1)

You're right that what I said is incorrect. I'll blame it on the hour and bottle count when I wrote it...obviously, weight transfer IS desirable and even necessary, without it there would be no contact patch management. I'll attempt to correct it by saying "excessive chassis movement" is not desirable, instead of "weight transfer" is not desirable. Perhaps, hopefully, that makes more sense.

I should have just asked if anyone was successfully running spring rates lower than 550/450-ish, and left it at that. lol

I take it with your 550/350 split you have a significantly stiffer rear sway bar, as well?

Thanks for taking the time to point out my error in a decent manner, even if it does still make me feel a bit dumb

ion_four

iTrader: (1)

Oh, btw. I just realized I've read over...hmmm...all of your blog and enjoyed it. Thanks for sharing.

Kennetht638

iTrader: (2)

I was a bit vague about this, but actually the reason why your statement was incorrect is because stiffening the car has no effect on weight transfer except for a tiny contribution from body roll that most would consider negligible. Even cars without suspension have weight transfer. However, the distribution of stiffness from front to rear affects the distribution of weight transfer. If you do want to learn, I'd recommend doing some reading in a book like Fred Puhn's "How to Make Your Car Handle"(Disclaimer: I haven't read this book, but I've heard good things about it). If you just want answers, I think that an RX8club member LionZoo had tried running his car at 300/300 with early FatCat Motorsports dampers (here's his thread) I have no idea what happened to him though but maybe you could ping him to find out. Beyond that, I don't think many at the top level have been running that soft in the front.

To answer your question about my setup, I have an ultra-stiff front bar set on full stiff and my rear bar is on soft, so like I mentioned a couple pages ago, my car is about 68% front-stiff.

I think we went through this a bit with Nathan Atkins just a couple pages back, but I'd say that if your desire is to race, just go with something proven. If you want to tinker with things or think you have a better solution, definitely try it and report back! I just think you should have some solid justification for it before you sink precious resources into it. I'm an engineer and I like to do things in engineer-y ways, but even I've found that if I just do the basic math, the car setup that I'd come up with would be undriveable. In this case, where the variables are way more complicated than it's worthwhile to model, empirical testing trumps the analysis that I'm willing to do.

Thanks! I don't update enough, but I'm glad somebody is reading!

ion_four

iTrader: (1)

I actually own that book you mention, but haven't read it in many years and perhaps that's showing...Vehicle dynamics are indeed quite complicated. I do want to learn more and I enjoy working on vehicles, at least as much as driving them. I'm a DIY'er to a fault, really.

I have some bilsteins that I'm going to revalve for 325/250 for next season, as I had some 2.5" springs laying around from a car of the past...If that's a miserable failure, then I'll put the front shocks/springs on the rear and revalve the rears for ~500lb springs and put those on the front (yes, they're double-eyelet type shocks, so this should be simple if I make a clevis mount for the front that is interchangeable.)

I will report back, as long as it's not thoroughly embarrassing.

Also, you definitely should update you're blog...has it been a year with no RX-8 updates?!

JeffH

In line with Kenneth, when driven correctly most RWD cars are fastest with a higher front roll stiffness. I'm over 71% but have a stock lsd. His OSG I'm thinking requires a different setup to work. On 245's I'm closer to 75% with a bit of positive rake. Then again I'm using .55F/.50R motion ratios for the sway bars that could be off.

Nathan Atkins

Yup I wanted to try something similar too, let me let you guys know what I ended up with.

My goal was to choose spring rates such that I had about 65% FRC without having to replace any sway bars. I ended up choosing 560/392 (which is 10k/7k) for the springs and removing the rear bar. The car feels pretty bang on that way and was good for a WDCR STX win last week from a field of 15 and PAX'ed 10th overall.

What I'd like to do is reduce the front spring rate to 392 and instead use the 27.2mm bar with 5.5mm wall thickness I found online, which according to the math produces the same FRC I have now and very similar overall roll stiffness, but should induce more weight transfer to the rear on corner exit to help put power down and reduce some pesky wheel spin I get occasionally.

I may, I may not, but what I have now seems to be working, I may just leave well enough alone. Ion feel free to experiment if you have the resources but Ken raises a good point about having some faith in what's out there. The stuff generally works right out of the package. That said I've really learned a lot along the way and that has had a lot of value to me, and I've wound up with a pretty competitive setup for right around $1k (Jeff feel free to travel down to DC and humble me anytime :-)

Oh I forgot to mention, my goal was 65% but I ended up at 67.7% which I was told would be tight! but it actually feels just right here.

Nathan Atkins

Jeff your sway MR are pretty close to what I'm using, I got 0.604F and 0.509R for sway bars from Shaikh at FatCat

Kennetht638

iTrader: (2)

I'm using the same MR's as Nathan, so with your MR's I'd actually only be at 65% which means that you're even more front-biased relative to my car than the numbers say. Also, I switched back to the stock torsen for this year because the OSG was giving me trouble and so far the car has been much improved. For anyone paying attention, this is very illustrative of how easily the results can be muddled by things in the setup that aren't captured by the simple natural frequency calculations. For example, ride height affects obvious things like CG and roll center height as well as position in camber and toe curves, but it will also have effects in things that you might not consider like sway bar rate linearity and even bushing rate linearity.

Ion, I'm sure you can tell from my blog that I also like to fiddle with stuff even when there's a proven solution out there, so I definitely encourage you to try new things. And even if it is embarrassing, let people know so that the next guy who asks won't have to go through it again! You'll only get made fun of a little bit I'm sure.

ion_four

iTrader: (1)

I'm definitely all about trying different things and have my own ideas (obviously). Frequently, they end up in the toilet, but once in a while I have a creative idea work out quite well and then I get to feel like a smarty pants, so it works out in my book. Hey, none of us are following the pack, since we have 8's!

Since I have the springs, I'll probably valve my shocks for the 325F/250R and go with a stiffer front bar. This SHOULD be very similar to your and Jeff's (winning) set-ups, but overall just softer. With no exaggeration, my local venue is pretty unbelievably uneven and rough...it's bad enough that the Oregon Region SCCA club does most of its events 2 hours into Washington...I've been up there and the difference is vast...faster, smoother, etc. I just haven't had the time this year to make it up there except for an EVO school.

Ultimately, my goal is to do some national level type events, but 1) that probably won't be next year, and 2) swapping some shocks/springs around for a different venue isn't too big of a deal, if I end up getting my act together sooner rather than later. Oval track guys swap springs/shocks all the time So, going with a better, but potentially not optimal set up, will just be part of the learning curve. As long as I keep the cost low enough, it won't even hurt the wallet.

I do find it interesting that the successful setups have such a large front bias. I suppose this requires an alignment with much more negative camber up front than in the rear, and perhaps more toe out in the rear to allow the car to rotate? Or, perhaps I need to do more research on that, too.

JeffH

Well this got me thinking and didn't want to screw anyone up if my numbers were off. I realize I may have been doing the calcs wrong with doubling the sway bar force to compensate for roll. Without the doubling the force I'm at 67.5% for 255 RS3's and 69.25% for 245's on somewhat grippy asphalt. So no need to re-evaluate your setup.

I typically run as much rear toe in I can get away with. Around 1/4" using toe plates/string.

fossumja

iTrader: (4)

So what happened to all the 8's at Nationals? Granted I had to bail myself and likely would have run Jason's Scibaru if things had gone to plan...

TeamRX8

iTrader: (25)

DKNVs daughter Rachel won CSL in the family RX8, it has the my stock class FSB & Koni DA shock setup

DKNV has a 2009 BSL and a 2012 STXL championship in my RX8, she must be proud for Rachel to bring another one home for the family

BRODA

iTrader: (7)

Big congratulations to all the past, current, and future RX8 owners who took home trophies from Nationals.

I know at least six trophy spots in STX went to members of this community, with several more within a few tenths...

I had a ton of fun, met a lot of great people, and saw some old friends. Participating in the largest class ever at the largest Nationals ever was very cool, and the competition in STX was fierce. Very glad I made the trip this year.

See y'll next year.
- DT

Nathan Atkins

I had gone the safe road with my spring rates earlier and got something sort of similar to whats available off the shelf, (10k/7k)

they work pretty good with the stock 1" front bar and no rear. FRC is about 67% and i like the way it feels on course.

I'm acquiring a set of standard 2.5", 8" length, 500#/in hypercoils from a buddy for a song. Coupled with an RB front sway and moving my 10k's to the rear, this should keep the FRC right at 67%(assuming the same material properties for the RB sway as stock)

So to anyone who subscribes to FarNorthRacing's writeups, this set up will give 2.2/2.5 natural frequencies, and a 67% FRC. All Ive got to do is valve accordingly.

This will likely be a winter mod so no data until next season probably, but I'm hoping to get some good results. I'll keep you guys posted.