Steve Dallas

Answers to your questions:

1. No one that is fast uses Koni shocks. They can handle about 30% more spring than OEM before needing to be revalved. That is nowhere near enough. The rears are only adjustable after partially removing them from the car.

2. The PSS is a much better option. The shocks are properly valved for 2.6x more spring than OEM, and while more street oriented, they put up respectable lap times at the track. You have to spend a lot more money to do much better, IMHO, with 1 possible exeception.

3. If I were in your shoes, I would take a long hard look at Feal coilovers. For not much more money than PSS, you can get a custom setup designed for the track that includes Swift springs in your choice of rates. I wish I had an excuse to try them.

A few more thoughts on your application:

1. You want to keep your front to rear spring ratio close to 1.5. Anywhere between 1.4 and 1.6 yields good balance.

2. The RX-8 handles best with a heavy front bar and very little rear bar. I am running a Progress MX-5 front bar on full stiff with a 12mm OEM MX-5 rear bar. Your Hotchkis rear bar is probably too much, and you will probably find yourself wanting to go to the OEM 16mm or even smaller. A lot of people run without a rear bar.


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elford_tim

Yellow Konis are usually designed to work well with stock springs or springs slightly stiffer than the OEM springs. If you want to run much higher spring rates you either have to get them revalved or check if there are race shocks available.

Nadrealista

Are you trying to say that Wankelbolt is slow

some miata folks called koni and looks like upper limit is 450 lb/in, but upper limit is probably not = optimal

"According to Lee Grimes at Koni North America, the Koni Sport shocks are good for springs up to about 450 lbs and beyond that he recommended a re-valving of the Sports or a switch to the Koni Race shocks."

Interesting you mentioned in the other thread that PSS were much more neutral feeling than ohlins - which is what I am after. to preserve the neutral feel of the car while reducing roll. I am not interested in having the fastest lap time but rather having most fun while carving out the corners.

where did you say I could get PSS B14 for under 900?

Steve Dallas

LOL! Well played!

450 lb springs would definitely be short of optimal. Stock Konis are not going to control that much spring.

There are a lot of Miata guys running Koni yellows at my home track. Most of them only do it to stay within class rules of some other activity, and practically all wish for something better. None of them can hang with my much heavier Miata on its FM Fox suspension.

I have a suspicion that Koni over-sells the capabilities of their shocks to pump up sales. Also, they are a sponsor of SCCA and other organizations that are in a position to set rules that are beneficial to their product lines.

The sub $900 PSS thing was a coupon code with free shipping a while back. The best I can find right now is just under $1100. Still a good deal, but pretty close to the price of Feal.

IamFodi

iTrader: (1)

Steve, do you remember or did you record the weights of the Ohlins fronts and rears on their own?

Steve Dallas

I did not think to do that. Sorry.

Nadrealista

this article that talks about choosing the right spring rates for rx8. it is interesting that car was hitting rear bumpstops even with 450/280 spring rates (on BR-series coilover kit). they had to go to 560/392 spring rates to improve.

given that stock spring rates are much lower you could think that stock suspension is made to use bump stops by design...

Steve they also mention how to use zip-tie trick to see if you are hitting bump stops, maybe you can try it.

http://www.superstreetonline.com/how...ect-mazda-rx8/

9krpmrx8

iTrader: (46)

Steve won't make it past BC "racing" coilovers.

blu3dragon

iTrader: (1)

That's because it is designed to use the bump stops :-)

9krpmrx8

iTrader: (46)

Yes.

https://www.youtube.com/user/SuspensionTruth

Nadrealista

then the question is what the stock spring rate changes to when you get into bumpstops:

1. plain stock suspension

2. stock suspension plus big hotchkis bars (which is what I have)

found these bumpstop curves for rx8 from FCM, looks like 150/100 lb for the first inch of travel then it gets very stiff for the next 10mm of travel 300/225lb:

Steve Dallas

The article provides tacit evidence that BC has no idea about racing and probably never tested their "racing" coilovers in an actual RX-8 before. They should know about shorter, progressive bump stops, and should have included them. They should also know how much spring is needed to provide enough bump travel front and rear for a given shock length in a "racing" setup. Apparently they don't. Also, a 1.2 second improvement over the stock suspension is not terribly impressive. My Ohlins coilovers, which are not ideal for track use, are over 4 seconds faster than my stock setup was on the same tires. So, I'd say those guys created more style than grip.

The spring rate info in that article probably does not travel well. ( <-- pun thataway) BC uses their own billet rear mounts, which limit bump travel to be pretty short. Stiff springs and short bump stops are obvious requirements in that approach.

I do know about the zip tie trick. I don't need to use it, however, because my bump stops tightly hug the shock rods and stay put when moved, and because I feel it when I hit them. I know I hit them. The question is: am I hitting them at times and/or in ways that would upset the car enough to unbalance it into snap oversteer? I believe the answer is yes. I just haven't done anything about it yet. I have been focused on my Miata for the past several months. The perplexing thing for me has been that I never had such problems with my PSS9 setup, with its lighter front springs and similar rear springs. The difference is probably the 2.0 vs. 1.4 ratio.

Tein makes tapered springs that should fit my rear coilovers. I may experiment with bumping the rear ~1K from 224 to 280. That would move my front to rear ratio from 2.0 to 1.6 and provide some extra bump travel. I can't do much more than that without having the shocks revalved, and it would start to make sense to look at other options at that cost.

Nope.

Yep. Within certain design parameters, the system works very well.

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blu3dragon

iTrader: (1)

My vote would be for the b14 kit. You then have the option to customize spring rates & have them revalved in the future if you want.

If you are looking for a custom setup, it is worth giving fatcat a call as well :-)

blu3dragon

iTrader: (1)

Are you trying to work out what spring rates to get? (I'm not sure why you are trying to calculate the added rate of the bump stops). Stiffer springs will mean you are using the bump stops less, but I think you would have to go too stiff if your goal is not to use them at all.

Nadrealista

just trying to figure out wat is my effective spring rate is with stock suspension and hotchkis sway bars. then from there I can better understand how much spring rate is needed to improve car cornering capability while keeping the grip level high.

my current spring rates are much higher than stock when you factor in additional spring rate from sway bars. so question becomes what is better for track use:

1. softer springs and stiff bar

2. hard springs softer bar

I was just looking installation manual for B14 and B16 system. Both use same springs, dampers are different and B 14 tells you to keep OEM bumpstop on the fronts while supplying theirs for the rears:
http://cart.bilsteinus.com/pdfs/E4-WM4-Y547A00.pdf

according to these part numbers spring rates for both B14 and B16 are:

front 442.6 lb/in E4-FD1-Y412A00 342.6 lb/in and helper e4-fd1-y504a01 @ 80 lb/in
rear 240 lb/in E4-FD1-Y805A00 240 lb/in

that makes f/r ratio 1.84

on the other hand goodwin states that b16 rates are higher?

"The RX-8 PSS9 rates are 370+145lb/in helper spring front and 375-445lb/in progressive rear."

Steve Dallas

I agree. The PSS kit will keep you happy for a good 2 years, while you work on the nut behind the wheel. Beyond that, you can increase spring rates ~30% without re-valving, or increase them more and have them re-valved by any of a number of Bilstein shock gurus, including FCM. The PSS kit is a good investment. (The PSS9 kit is not a good investment, however, because the rebuild costs are high, and many shock rebuilders will not touch them.)

The only other good option in (what I assume is) your price range is Feal. I base that solely on what I have read from people I trust, like Ryan Passey at GWR. Miata guys are winning races on them.

Fortune and ISC might be worth looking at, but I can't articulate why, with Feal at the table.

Don't even think about anything else priced under $2,000. It is all junk compared to the above.

On the used market, a set of KW V3s might be an option.

Sway bars affect roll couple/stiffness much more than they affect spring rate. Spring rate and sway bar stiffness work in concert to control roll, where spring rate is considered dominant, and sway bars are used for fine tuning. The best approach I have found is to start with stock bars. Find the proper spring rates for your desired ride height, bump travel, and natural frequency. Then, calculate how much additional roll couple you need, and add or subtract bars to reach the target.

1. This approach is often taken by guys looking for good street manners and track performance or guys who are constrained by class rules. Trying to have it both ways rarely works (ask me how I know). What you will end up with is a car that is compliant enough on the street, but the steering will be stiff feeling and darty. On the track, anti-roll may be adequate, assuming an aggressive alignment. Turn in will be quick, aggressive, and imprecise, while the car takes a while to transition and set at the same time. Tendency to squat and dive will be exaggerated, which affects grip--especially under throttle and braking. Cornering will be unpredictable, and matching tires to the capabilities of the shocks and springs will be paramount. This approach will very much limit your tire choices.

2. This approach yields a faster car, and it is how race cars are built. It can be comfortable on the street, assuming the spring rates are not crazy high and the shock valving is very good. Targets are set for all the usual aspects of handling (normally starting with tires), and appropriate parts are chosen to meet those targets.

3. My approach for this car was a bit of a hybrid. I attempted to go with just enough spring and just enough bar to actually yield a competent dual purpose setup for just enough tire. And, I mostly succeeded. The "complaints" I have had about this setup have been related to trying to find the last 10% of performance. My car is fast on its current suspension. I just want it to be fast-ER. As a reminder, I am running medium springs, a medium front bar, and a very small (11 or 12mm, depending on conditions) rear bar. When I was running PSS9s, I had medium-low springs and medium bars front (medium setting) and rear (soft setting).

All that Bilstein stuff is indeed confusing. So, I called Bilstein tech support about 3 years ago and asked for the straight dope. The effective rates, which are the ones that matter in practical application, and should take helpers and progressive springs (how does one do that?) into account as much as possible, were given to me as:

PSS
370F 240R = 1.54

PSS9
340F 240R = 1.42

Obviously, I can't swear this information is correct. It's just what they told me. I can say the Ohlins fronts at 457 are definitely stiffer than the PSS9 fronts were.


BTW, yer killin' me with this ninja edit stuff. Just make new posts.

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IamFodi

iTrader: (1)

So Steve, correct me if I misread, but you seemed to feel VERY positively about the Ohlins kit at first, and some of your comments implied a fair bit of confidence in the car's handling. Now, things seem... still positive, though with more qualifications. Is that about right?

Steve Dallas

That sounds about right.

This is a good opportunity for context and clarification. I suppose I have done some grousing since I installed the Ohlins coilovers. I do not mean to impart that I am unhappy with them--quite the contrary is true. I very much like them. They are excellent dual-duty coilvers in their stock form. The progression of thoughts and feelings went something like this:

1. Ecstasy at being able to instantly drive 2 seconds faster on the same tires
2. Boredom with newfound speed; always looking for more
3. Pushing new boundaries reveals weaknesses for track duty
4. Frustration with fine tuning, because suspension does not follow tidy rules
5. Epiphany at finding extreme change works whether or not it makes sense
6. Ecstasy at being able to drive...
7. Joy of bringing home Miata to take things to the next level

I have never disliked my Ohlins setup. I took it farther than Ohlins intended and revealed the bad habits around the edges of its capabilities as a hybrid setup. Then, I reached a level of mild frustration that they would not perform beyond their intended purpose / design spec. Because I'm a maroon.

It was legitimately frustrating that I could not quickly and cheaply dial it in as I have other setups, partly because none of the normal rules seemed to apply. Add to that the fact that, when the car would misbehave on track, there was no obvious reason why, so no clear direction in fixing it.

I keep comprehensive notes on everything about how the car performed on every track day. I can comb through and condense those into a narrative of what the car was doing, what I did to attempt to fix it, and what the results where, if anyone is interested.

The current solution is to use very little rear bar and drive with a little extra corner entry understeer (which is actually quite fast). The future, hopefully more comprehensive, solution is to either add 1K rear spring using GWR's kit or add 1K front and 2K rear spring using Tein tapered springs, which might require a re-valve.

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IamFodi

iTrader: (1)

I'm interested! This would be awesome.

If the normal tuning rules don't apply cleanly to this kit, and if it was hard to find reasons for its misbehavior (would love to know more about that BTW), the reason must have something to do with the dampers, right? Because the rest is just spring, and there's nothing magic about a linear-rate spring. This reminds me of some cryptic but dire feedback I got from some of my friends about the Koni FSD damper kit; they said it was great up to 8 or 9 tenths, but it "goes to ****" above that. I'm sure the Ohlins dampers are much better sorted, but I wonder if there's something about the DFV (which I don't think is too different from FSD) that makes this a special kind of beast.

Nadrealista

my new 17x9 konig hypergrams with 255/40 NT01s on them arrived yesterday. they tip scale at just under 44lb and have 1" wider contact patch than my worn 245/40 18 NT01 on S1 wheels.

will be interesting to see how will stock suspension with hotckis bars set to firmest cope with extra grip on the next track day :-)

Steve Dallas

The main incoherent part of the journey had to do with spring rates. If my Bilstein information is correct, I increased front rates by a net of about 105lbs by installing Ohlins. That should induce some understeer, which should mean I would need a little less front bar or a little more rear bar. The opposite occurred, however. When set up "correctly," I experienced massive oversteer everywhere. From there, I did all the normal incremental adjustments: ride height, tire pressures, sway bars, rebound, alignment. Things got marginally better, but never "right" like it had been before.

One day, while frustrated at the track, I crawled under the car and just disconnected the rear OEM bar on one side. That resulted in manageable understeer, and that was the epiphany. With a tiny little MX-5 rear bar, the car is mostly neutral, but it still has a tendency toward snap oversteer when pushing it really hard. As mentioned before, there is really no rhyme or reason to why it happens, so there is no obvious fix. I could probably sort it out if I had a toolbox at the track and all day to try random things, but I never have that opportunity.

It could be something in the magic valving acting up at the extremes. I, too, have wondered that. I have heard the same thing about Koni FSD shocks. Maybe the rebound falls off and allows a spring to launch one or more corners of the car just enough to cause it to lose grip, but not enough for me to feel it from the factory seat?

At this point, I am ready to listen to the voice inside my head that is telling me, "You have reached the limit of what this hybrid setup can do, so stop punishing us and enjoy your car!" and focus my time and car money on the Miata.


Why 255s? You would get the same contact patch from 225s on those rims, have stiffer sidewalls, have lower tire pressures, and enjoy less weight.

Nadrealista

I was going to do just that, but I called Nitto and talked to their engineer. He said 225 would be suboptimal on the 9" rim and they don't even list is as a approved rim width for that size. We also talked about the contact patch and he said 225 thread width would be 8.36" (8.86-.5) where 255 is recommended for 9" rim and will have thread width of 9.85".

so I decided to take just under 2lb penalty per corner for more than 1" gain in the thread width.

also 255 were on super sale so I got set for $520!

on the right is same nto1 245/40 18 on S1 8" rim

Steve Dallas

Yikes! You need an alignment for allthecamber!

Lay a ruler across that new tire and snap a pic, if you don't mind.

Nadrealista

well with these tires car sits .5" lower so hopefully that will help me get a bit more camber.
will take it to the local Firestone where I have lifetime alignment to see how much camber I can get now.

I did check last night it was just around 9.5".

at work now :-)

Nadrealista

also intresting is that given their load rating I should run them at 26psi cold pressure, but that seems pretty low to me?

stock tire supports 1227lb at 32 psi

255/40/17 nt01 supports 1396lb at 32 psi

to match stock load of 1227lb I would have to run new tires at 26psi

here is example toyo uses: