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Here is some interesting data on the Bilstein B14 PSS kit vs. the B16 PSS9 kit. According to the technician I spoke with the other day...
The B14 PSS kit has spring rates of:
371 linear + 79 tender front
239 progressive rear
He said the literature does not have the operating range of the progressive rear spring.
The valving of the shocks is medium-firm for compression front and rear with above average rebound front and below average rebound rear. He cannot give me the specifics, because they are proprietary.
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The B16 PSS9 kit has spring rates of:
340 linear + 79 tender front
240 progressive rear
The valving of the shocks is firm for compression front and medium-firm rear with adjustable-ish rebound all around.
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What is surprising to me is the lower front spring rate on the PSS9 front springs. I also thought the rear springs were much stiffer than they are.
Also, the spring rates published in the PSS9 threads on this site are either incorrect or have changed since the posts were made.
The front tender spring is not factored into the spring rate when the car suspension is loaded. There is speculation in some other threads that the tender spring increases the front spring rate somewhat, but it does not according to Bilstein. They are helper springs and not assist springs.
Just thought some might find this information interesting and wanted to post it in light of the incorrect information in other threads in case people search for it.
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I have corrected some information in my posts above, which makes some of them make even less sense than they did before. Ohlins doesn't look so crazy now, does it?! Of course, since I had my rear springs being much stiffer than they really are, that makes the rates FCM is recommending quite different than what I am running now, which changes the equation somewhat in my mind. Those spring rate changes are quite a bit larger than I was led to believe by the incorrect information I had.
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Last edited by Steve Dallas; 11-10-2015 at 09:58 AM.
Yet, if FCM really is the bees knees, and I can totally take suspension out of the equation and focus almost totally on the driver, does that make the cost worth it?
The truth is it's easy to drive a fast car fast. Only the skillful can drive a slow car fast.
If you learn how to drive fast in a slow car, your skills will increase more quickly and you will have skills other drivers with fast cars don't have. Think momentum preservation and really being able to control a sub-par suspension at the very limit of traction. I learned how to drive fast in a no-horsepower first-gen RX-7 with prehistoric suspension, tiny tires, and a tendency toward snap-oversteer that would surprise a veteran Porche 930 racer. That car taught me how to drive a car on the ragged razor's edge, to be light but quick on the steering, and how to use every inch of the track to save every MPH I possibly could. Back when Spec RX-7 was the most popular class in local SCCA racing and for years after, all the fastest drivers in other cars and classes started in Spec RX-7. Now when I get into a car that has actual handling or useful horsepower, I can also drive it very fast very quickly. I can also drive my RX-8 with excellent handling but an officially "dead" engine fast enough to embarrass much more powerful and expensive machinery on the track.
So my opinion is you will learn more as a driver, and faster, with an inferior suspension than you will with a perfect suspension.
Once your skills have advanced far enough that you have reach the limits of the suspension and you are very conscious of it holding you back like I have with my Koni setup, then upgrade to the best suspension you can afford. That's why I'm considering FCM now after tracking my '8 for 8 years on the current setup.
The other consideration is that if you aren't racing for a trophy or money, would you rather spend money on more days at the track, or more money on suspension leaving you with fewer dollars for track days?
^very interesting update on the spring rates. Thanks for sharing. Actually those rates make more sense than the originally posted values since they more closely track the stock ratio and so will work with the stock ratio sway bars, and explains why you needed to add stiffer front and rear bars to get the balance right (rather than just a stiffer front bar).
The FCM recommended values require a change in the ratio of sway bar stiffness to maintain a neutral handling setup.
You probably already know this, but the primary difference between 371 front on the PSS, compared to 340 front on the PSS9 will be to add a little more understeer (or slightly less oversteer). This is in the realm of fine tuning and might be based on feedback of the PSS9 rates, or to compensate for differences in the shock valving.
Going back to your last post on the previous page - $700 to rebuild your current suspension, change the spring rate and set the valving to match seems like a very good deal. I guess now you will want to investigate increasing the rear rate as well, but even with that added cost this seems like a good option.
FCM is also a good option. It's really up to you decide where your priorities lie :-)
The truth is it's easy to drive a fast car fast. Only the skillful can drive a slow car fast.
If you learn how to drive fast in a slow car, your skills will increase more quickly and you will have skills other drivers with fast cars don't have. Think momentum preservation and really being able to control a sub-par suspension at the very limit of traction. I learned how to drive fast in a no-horsepower first-gen RX-7 with prehistoric suspension, tiny tires, and a tendency toward snap-oversteer that would surprise a veteran Porche 930 racer. That car taught me how to drive a car on the ragged razor's edge, to be light but quick on the steering, and how to use every inch of the track to save every MPH I possibly could. Back when Spec RX-7 was the most popular class in local SCCA racing and for years after, all the fastest drivers in other cars and classes started in Spec RX-7. Now when I get into a car that has actual handling or useful horsepower, I can also drive it very fast very quickly. I can also drive my RX-8 with excellent handling but an officially "dead" engine fast enough to embarrass much more powerful and expensive machinery on the track.
So my opinion is you will learn more as a driver, and faster, with an inferior suspension than you will with a perfect suspension.
Once your skills have advanced far enough that you have reach the limits of the suspension and you are very conscious of it holding you back like I have with my Koni setup, then upgrade to the best suspension you can afford. That's why I'm considering FCM now after tracking my '8 for 8 years on the current setup.
The other consideration is that if you aren't racing for a trophy or money, would you rather spend money on more days at the track, or more money on suspension leaving you with fewer dollars for track days?
Obviously, I cannot disagree with anything you wrote. That is one reason I have not moved beyond DOT summer tires. I know R-comps will hide a lot of my mistakes, and I want to know about those mistakes. Once my rubber starts holding me back, I will look at making that leap. The same can be said for suspension, although to a somewhat lesser degree, methinks.
The impetus for the upgrade is having to do something. And, if I have to do something, I might as well look at upgrades rather than simple replacements. I was pretty happy with my suspension the way it was--I just needed to solve the tire wear problem. If I didn't have a blown shock, I would just be looking at tweaking things around the edges to fine tune my setup.
As for the money involved, I am fortunate enough to not have to choose between equipment and seat time unless it is very expensive seat time or very expensive equipment. FCM is an expensive luxury, but it is not a very expensive luxury. Still, I want the investment to be worthwhile and need to perform due diligence in that regard.
[The CoTA thing is really not in the cards this year for a variety of reasons.]
Originally Posted by blu3dragon
^very interesting update on the spring rates. Thanks for sharing. Actually those rates make more sense than the originally posted values since they more closely track the stock ratio and so will work with the stock ratio sway bars, and explains why you needed to add stiffer front and rear bars to get the balance right (rather than just a stiffer front bar).
The FCM recommended values require a change in the ratio of sway bar stiffness to maintain a neutral handling setup.
You probably already know this, but the primary difference between 371 front on the PSS, compared to 340 front on the PSS9 will be to add a little more understeer (or slightly less oversteer). This is in the realm of fine tuning and might be based on feedback of the PSS9 rates, or to compensate for differences in the shock valving.
Going back to your last post on the previous page - $700 to rebuild your current suspension, change the spring rate and set the valving to match seems like a very good deal. I guess now you will want to investigate increasing the rear rate as well, but even with that added cost this seems like a good option.
FCM is also a good option. It's really up to you decide where your priorities lie :-)
Everything you wrote there whizzed through my head when he told me the spring rates. Interestingly, Goodwin has the wrong rates on his site, too. Behold:
Brian's Application Notes: The PSS9 is Bilstein's dual purpose setup for the guy looking for something competent on street and track while still riding very well on the street. The PSS9 adjustment ***** have easily determined clicks...and mostly changes rebound. The range is wide and each click of the **** has a noticeable change; making precise dialing in of your RX8 easy. The RX-8 PSS9 rates are 370+145lb/in helper spring front and 375-445lb/in progressive rear.
Right now, I am leaning toward having my setup rebuilt and bumping the front spring from a 6K to a 7K. The Bilstein guy confirmed it would be fine even with the stock valving, which would actually favor the stiffer spring. There is actually a precedent for doing it here. Still need to do the math to make sure I am not upsetting the car's natural frequency too much by doing that, though. I can drive on that for another year, and look at FCM again at that time or when I wear it out again.
Those spring rates make a lot more sense with the troubles you're quoting. They're a fair bit softer than what I'm running for instance, and I've got stiffer sway bars, so it's no big suprise that you're rolling more and putting more stress on the tires.
I agree with the approach to get them re-valved locally with some mild spring rate increases. I like the 450/280 spring rates that the KW's have.
Originally Posted by Steve Dallas
There is speculation in some other threads that the tender spring increases the front spring rate somewhat, but it does not according to Bilstein.
Spring rates DECREASE when stacked, unless as you point out, the tender is completely compressed.
Think of it like this, you take 2 springs of a 100lb/in rate and stack them on top of each other. Stick 100lbs on top and EACH spring moves 1", for 2" total movement. This adds up to a 50lb/in spring rate overall.
Those spring rates make a lot more sense with the troubles you're quoting. They're a fair bit softer than what I'm running for instance, and I've got stiffer sway bars, so it's no big suprise that you're rolling more and putting more stress on the tires.
I agree with the approach to get them re-valved locally with some mild spring rate increases. I like the 450/280 spring rates that the KW's have.
Spring rates DECREASE when stacked, unless as you point out, the tender is completely compressed.
Think of it like this, you take 2 springs of a 100lb/in rate and stack them on top of each other. Stick 100lbs on top and EACH spring moves 1", for 2" total movement. This adds up to a 50lb/in spring rate overall.
Agreed all around.
As for assist springs changing rates, I agree with you. It is kind of like stacking capacitors in series. If they are of equal value, the resultant value is halved. Hyperco has some excellent information about how springs behave on their site in the tech section for those who might be interested.
Considering the valving forces I have in play, I may have to suck it up and go with stiffer in sway bars to control the roll I am experiencing, although I want to maximize camber as much as I can before making that determination. Off-the-shelf shocks are limited in critical damping, thus roll control, which may force my hand. I am on the middle setting on my front bar, so adding -camber and switching to the stiffest setting may get me there. The rear bar will be chosen based upon those results.
In conclusion, I still think I need to have my shocks rebuilt, increase the front spring rate slightly and possibly shorten the front bump stops slightly to increase front bump travel a bit, increase the stiffness of the front sway bar a bit, lower the car 1/4", revise my alignment to maximize -camber, inspect and replace any worn bushings, and do whatever is necessary to balance the handling of the car again.
I ordered some parts yesterday and dropped the car at the shop this morning. We shall see...
Sounds like a good plan for a reasonable cost solution.
One note though, shock valving won't affect steady state handling balance, since there's no shock motion, only how it behaves in the transitions (ie corner entry and exit).
Indeed, sounds good. One thing to be aware of (and apologies if this is pointing out the obvious) is that if you shorten the front bump stops, but leave the rears as is, then you will be changing the balance once the car gets to the bump stops. The effect in the dry will be as if you have softened the front spring rates.
I mistyped when I said I would trim the front bump stops. My beer-addled brain is focused on the front, but the rear will be equally considered in the end. The full suspension will be out of the car, so it will be easy to trim all of the bump stops should I decide to do it. The fronts appear to be pretty short at 40mm already, so I may trim 4 mm front and rear to bring the fronts down to 36mm. It isn't much, but we're fine tuning, right?
The good-ish news is, the shop inspected my bushings and did not find enough wear to warrant replacing any of them.
The bad news is, the manager thought I had PSS rather than PSS9, and he does not want to open them up for fear of what he might find in there. He wants to send them off to Bilstein for $275 each. Where have I heard that before? At least he is honest about it.
The good news is, he only charged me $50 for 2 hours of shop time.
1. FCM ($2700-$3400). Already discussed ad nauseum. I'm still very intrigued.
2. Ohlins DFV ($2300-$3300). The only thing I have to add to this is the folks at Goodwin all run them and swear by them. The gist is they are the best off-the-shelf coilovers available in their opinion (but not worth the extra money over PSS series according to Vorshlag). They even claim to like them better than FCM. Some of them like the stiffer springs and some like the softer springs. The way ride height is controlled is superior to all other products in the price range, and the upper mounts with spherical bearings are thought to be superior. They are also the lightest weight option. Of course, they want to sell me some expensive coilovers, so that angle has to be considered.
3. Bilstein PSS ($800). I can't know what these are about without trying them, but to get back on the track for only $800 is mighty tempting. I have been pretty fast on the PSS9s, and these aren't that different (supposedly) considering the settings I use. Since they are not adjustable, no one will be afraid of working on them, and the work will be relatively inexpensive. That means they are future-proof. I could drive on these for a while and send my PSS9s to Shaikh at my leisure for his treatment and end up with the opportunity to choose between them for about the same price as buying new FCMs outright. If I should choose the FCM setup, I could either sell the PSS at a small loss (Excellent condition! Only 2000 miles!) or just keep them as a spare setup, which I have just proven I need if I want to stay up and running during unexpected repairs. Should I not love the FCM kit, well, that would really suck. An FCM rebuilt PSS9 setup is probably worth a lot less used than their regular offering, and it would be weird to have something so expensive as a backup (cough, Peyton Manning).
4. Bilstein PSS + FCM ($bazillion). Didn't I just ramble on about this? Wait. Humor me for a moment. What about buying a PSS setup and waiting for a lightly used FCM setup to show up in the trading post or on eBay? From what I have read about various FCM setups, they are all pretty similar for this car. I could end up with the same situation as 3 above with a little patience, except I would still have the PSS9s with which to do something or other for whatever reason I can't think of right now. Surely that is important in ways which will be revealed to me in the future. Right? Nah. Will probably just take up space in my garage, but save me some money? Maybe? Anyone want to buy a set of well-loved PSS9s with a blown left front shock? No. Seriously, the used FCM setup would lose no value upon resale should I not love it. Risk mitigation if you will.
Decisions... Decisions...
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Last edited by Steve Dallas; 11-18-2015 at 10:28 PM.
Sorry to hear it did not go to plan with the PSS9 rebuild. On your remaining options...
That Bilstein PSS setup for $800 seems like an absolute bargain. Hard to resist that temptation and I thought you were set on this at one point... Can't complain at the spring rates for the price, or swap out the springs and consider getting them re-valved locally either straight away, or some time in the future.
Ohlins DFV seem like a great choice as well and at 2300 for the street friendly version also seem like really good value. My issue here is that for this price and the amount of track time you do I think you will want stiffer springs. That takes you to their custom setup and that brings them up to the same price (and lead time?) as an FCM setup. I don't know how they compare to FCM, I'd really like to ride in a car with a set to find out...
FCM. I have their basic setup (pre-dating KBO and ripple reduction), with spring rates similar to what you have been recommended. They are awesome on track. They work well on the street. I just inspected my shocks last weekend and all look good after 2 years, 20k miles and 24 track days. The shocks are not adjustable, but this actually means they are valved correctly from the start and I have never felt the need to adjust them. I expect you will be very happy with this setup. The down sides are price compared to the PSS and the lead time (but sounds like you can manage on your blown shock for a while as long as you don't track the car?)
I don't think you can go wrong with any of these choices :-)
^ Thanks, but I have pretty much ruled out KWs even at that price after a lot of research. But I am interested in his rims and tires. Thanks for the heads-up!
Long story short, about 18 months ago, I took a left turn a little on the fast side with traction control off, and some idiot pulled out in front of me in my lane without bothering to look just as I completed the turn (or was tracking out to the middle lane) within my dotted dashes. That caused me to swerve to the left, which caused me to spin and slam my right rear into a curb.
OK. I tried to frame that to my benefit, but the truth is, I should not have been going that fast on a city street, should not have turned traction control off, and should have remembered I was not running my track tires. My fault, really. Idiots are everywhere--myself included, apparently.
Anyway, I spent about $2500 fixing everything I broke that day. The right rear shock seemed to function fine, and I did not question it further after replacing the toe link, end link, bearing, brake line, rim and tire, etc. The shock must be functionally fine, because I have participated in many track days since then without noticing any problem.
I took that shock out last night to inspect it. I forgot that a spring compressor is a good idea on the rear (not necessarily needed on the front), so I wasn't able to comfortably open it up, but I'm pretty sure the rod is supposed to line up with the body. It doesn't. It doesn't show in the photo, but the lower bushing is split on the top half as if it were badly stressed.
[edit]
Just bent the mounting rod and not the shock rod, so this was repairable (yay for inverted monotubes!). I was able to put a thread protector on it and easily bend it back in a vise. The shock rod and seals are fine. Still have that bushing problem, though.
[/edit]
So, anyway, Ohlins or FCM?
Last edited by Steve Dallas; 11-23-2015 at 09:10 PM.
If you need the car back on the road, or were happy enough with your previous spring rates, then PSS.
If you can wait, and want a more track oriented setup, then FCM, and consider getting stiffer spring rates than you have been recommended.
Note that I don't have personal experience with the ohlins (so it's not that I don't like them, it's that I don't know to recommend them at their price)
Last edited by blu3dragon; 11-21-2015 at 09:10 AM.
What I am looking for is the proverbial pink unicorn that farts pixie dust and poops skittles. I want a setup that performs as well as possible on the track that does not beat me to death. Having it be reasonably compliant on the street would be nice to have. I am tracking my car 12-15 times per year now, but also still drive it to and from the track, on weekends, on date nights, to work on the occasional nice weather Friday, etc.
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this setup is possible, the shock is actually responsible for a significant portion of the ride quality, the spring really just sets the range of suspension travel that bumps happen in.
there are 2 valves in a shock, there is a low shock piston speed valve, and a high piston speed valve. the low speed does the handling, most shock shops can do this part easily. the high speed valve is for bumps, and most people don't really do much for this.
the trick to having good ride and handling is that the shock needs to be valved over the whole range.
so we're currently running a miata (i think we pitted next to Magnus at the nationals), we started with a spec miata suspension because its a miata, its rubbish.
next we went to an FCM setup, and the driver took a couple of laps, got out, said something about double condoms and then we switched to Ohlins. there is a little more to the story, but lets just say we didn't get along. Edit: about the double condom thing, if the optimum low speed damping book value is 65% of the spring, the ohlins are about 60%, and the FCM is 70%. so the FCM setup is still in the happy spot, but it is on the slower responding side, vs the ohlins which are on the quicker side. its almost a driver preference, some drivers like a slower easier car, and some drivers want the thing to respond faster.
the Ohlins are great, they handle well, which is the easy part. they also take bumps well, our drivers can hit curbs at full chat and the car just soaks up the bumps and doesn't get upset at all. plus it rides well. even after road racing for 13 years, the Ohlins are amazing.
re the spring rates. we've been racing for over a decade and we've always tested spring rates empirically, the miata being no exception. it is fastest with the spring rates in it, and we tried +/- 10%. the previous car was the same. we do use the maths, and it turns out of you compute the natural frequency of all the race cars we've done they are all 2hz in the front and 2.5 in the back. give or take 0.1hz.
there is a gotcha, when you have a car with bad weight distribution, like the honda, 2.5hz in the rear isn't streetable, bumps send it flying. the miata, and rx8 probably, are actually quite soft.
and the spring rates have some proportion to traction, so we ended up where we ended up on hoosiers, but if we were running R888's it might have been a little softer (less grip = less G forces = less body movement = less need for springs)
^so you didn't get along with FCM? Can you elaborate. Was this the 60% vs 70% thing, or was it elsewhere? I'm not trying to be difficult, I am genuinely interested as I look to possible future improvements of my own setup.
^so you didn't get along with FCM? Can you elaborate. Was this the 60% vs 70% thing, or was it elsewhere? I'm not trying to be difficult, I am genuinely interested as I look to possible future improvements of my own setup.
lol, yeah, his name got autocorrected and his email reply was this really long petulant rant. so its a personal thing.
the 60% to 70% is an analogy, if you want the other one, the driver said it was like wearing two condoms. so therefore it must be overdamped just slightly. the ohlins by contrast feel underdamped just slightly (the car is really soft and moves around a lot).
we felt that the overdamp, should slow the cars response a little, which in theory is less demanding of the driver, although it also removes some feedback.
lap times, given same driver/spring/bars/tires/track would probably be really similar, the ohlins is amazing over bumps and curbs, so i think it would be the faster setup, but probably only by a 10th or two.
this setup is possible, the shock is actually responsible for a significant portion of the ride quality, the spring really just sets the range of suspension travel that bumps happen in.
there are 2 valves in a shock, there is a low shock piston speed valve, and a high piston speed valve. the low speed does the handling, most shock shops can do this part easily. the high speed valve is for bumps, and most people don't really do much for this.
the trick to having good ride and handling is that the shock needs to be valved over the whole range.
Thank you for your insight.
That lines up with what I have been reading and have been told my local gurus. The consensus seems to be that once the low speed is chosen, the secret sauce goes into the high speed, which is a little more challenging to perfect. OTOH, Shaikh talks a lot about low speed being key, since the car spends most of its time there.
It seems there are maybe 3 camps. You have the independent guru, who does his best according to what he thinks is right. You have the mass manufacturer, who uses a compromise between what their engineers think is best, what marketing people want, what bean counters approve, and what their lawyers allow them to do. Then you have motorsports companies who just do what their engineers think is best as much as possible.
The question is whether to trust camp 1 or camp 3. And, it sounds like it comes down to personal preference for the most part. Excepting, perhaps, when they are so far apart on spring rates, etc?
Originally Posted by j9fd3s
so we're currently running a miata (i think we pitted next to Magnus at the nationals), we started with a spec miata suspension because its a miata, its rubbish.
next we went to an FCM setup, and the driver took a couple of laps, got out, said something about double condoms and then we switched to Ohlins. there is a little more to the story, but lets just say we didn't get along. Edit: about the double condom thing, if the optimum low speed damping book value is 65% of the spring, the ohlins are about 60%, and the FCM is 70%. so the FCM setup is still in the happy spot, but it is on the slower responding side, vs the ohlins which are on the quicker side. its almost a driver preference, some drivers like a slower easier car, and some drivers want the thing to respond faster.
the Ohlins are great, they handle well, which is the easy part. they also take bumps well, our drivers can hit curbs at full chat and the car just soaks up the bumps and doesn't get upset at all. plus it rides well. even after road racing for 13 years, the Ohlins are amazing.
There is a lot of FCM information out there in the Miata world, and after having spent 3+ weeks reading and talking to people, your summary appears apt to me. People who like more damping really like FCM, and people who don't, well... don't. The differences in lap times between FCM and other equally competent setups are very small, and are likely influenced more by driver preference and confidence than suspension capability.
There is precious little information on Ohlins DFVs in the wild that I can find, and almost all of it is positive. The main complaint is that they feel a little soft (softer than expected).
Originally Posted by j9fd3s
re the spring rates. we've been racing for over a decade and we've always tested spring rates empirically, the miata being no exception. it is fastest with the spring rates in it, and we tried +/- 10%. the previous car was the same. we do use the maths, and it turns out of you compute the natural frequency of all the race cars we've done they are all 2hz in the front and 2.5 in the back. give or take 0.1hz.
When you say, "the spring rates in it," do you mean the rates that come with the Ohlins, the spring rates from Mazda, or something else? Do you mind elaborating on this point?
Originally Posted by j9fd3s
there is a gotcha, when you have a car with bad weight distribution, like the honda, 2.5hz in the rear isn't streetable, bumps send it flying. the miata, and rx8 probably, are actually quite soft.
and the spring rates have some proportion to traction, so we ended up where we ended up on hoosiers, but if we were running R888's it might have been a little softer (less grip = less G forces = less body movement = less need for springs)
so thats my $0.02.
This is one of my hang-ups. I have used a couple of different calculators using what I know about the car, and I cannot get to 2.0F and 2.5R using any of the available spring rate combinations for this car.
Without going deep into the math, we can just look at front to rear ratio to see how far apart they are.
FCM 1.0 Stock 1.4
PSS/9 1.5 Ohlins DFV 2.0
Shaikh says he can get me close to there with his 1.0 ratio using similar 425LF/400LR springs according to his calculator. At the opposite extreme is Ohlins with a 2.0 ratio using quite different 460LF/230PR springs. What I am used to is right in the middle.
Which one is right? To which extreme should I go? It would be easy to conclude that Shaikh designs for the best track performance while trying to make it compliant enough for the street, and Ohlins designs for streetability first and track performance second. Track/road vs. road/track if you will. But, then I read reviews like the above where people LOVE them on the track.
I need more and better data.
Last edited by Steve Dallas; 11-23-2015 at 09:06 PM.
That lines up with what I have been reading and have been told my local gurus. The consensus seems to be that once the low speed is chosen, the secret sauce goes into the high speed, which is a little more challenging to perfect. OTOH, Shaikh talks a lot about low speed being key, since the car spends most of its time there.
It seems there are maybe 3 camps. You have the independent guru, who does his best according to what he thinks is right. You have the mass manufacturer, who uses a compromise between what their engineers think is best, what marketing people want, what bean counters approve, and what their lawyers allow them to do. Then you have motorsports companies who just do what their engineers think is best as much as possible.
The question is whether to trust camp 1 or camp 3. And, it sounds like it comes down to personal preference for the most part. Excepting, perhaps, when they are so far apart on spring rates, etc?
i think that is about right, the low speed damping is the handling, and the high speed damping is the ride. so yes the low speed damping is where the handling is.
the thing, for us, that separated the Ohlins from everything else is that the ride, and body control are just amazing, bumps do not upset the car at all (unless its low enough to bottom out), and it even rides nicely.
i did drive an FCM demo car, with crazy springs on the street, and its ok, but the Ohlins are better.
i should maybe say that we took those shocks off that demo car and won the western states TTE with them, so they aren't bad, the Ohlins are just better.
There is a lot of FCM information out there in the Miata world, and after having spent 3+ weeks reading and talking to people, your summary appears apt to me. People who like more damping really like FCM, and people who don't, well... don't. The differences in lap times between FCM and other equally competent setups are very small, and are likely influenced more by driver preference and confidence than suspension capability.
There is precious little information on Ohlins DFVs in the wild that I can find, and almost all of it is positive. The main complaint is that they feel a little soft (softer than expected).
i'd say this is right too. i drove the race car around at the miata pride parade, and its SOFT. the thing moves around a lot, but it feels really good.
When you say, "the spring rates in it," do you mean the rates that come with the Ohlins, the spring rates from Mazda, or something else? Do you mind elaborating on this point?
the miata DFV shocks come with really soft springs, and i think we started with spec miata spring rates, and went up until the car got slower, and then went back down.
This is one of my hang-ups. I have used a couple of different calculators using what I know about the car, and I cannot get to 2.0F and 2.5R using any of the available spring rate combinations for this car.
Without going deep into the math, we can just look at front to rear ratio to see how far apart they are.
FCM 1.0 Stock 1.4
PSS/9 1.5 Ohlins DFV 2.0
Shaikh says he can get me close to there with his 1.0 ratio using similar 425LF/400LR springs according to his calculator. At the opposite extreme is Ohlins with a 2.0 ratio using quite different 460LF/230PR springs. What I am used to is right in the middle.
Which one is right? To which extreme should I go? It would be easy to conclude that Shaikh designs for the best track performance while trying to make it compliant enough for the street, and Ohlins designs for streetability first and track performance second. Track/road vs. road/track if you will. But, then I read reviews like the above where people LOVE them on the track.
I need more and better data.
which means i should say my number is HZ. the really odd part is that we derived the spring rates empirically, by testing. its only later we ran the numbers and find that we're right on the book value, which is really weird.
i can give more specific details, but we're running a miata, so they may not apply
^ Right Hz. I understand. I just didn't want to get into natural frequency directly, because it is a lot more complicated to discuss on a forum. Rather, I went off into spring ratio, because it is easy to demonstrate that FCM and Ohlins are at 2 different extremes, where stock and Bilstein sit right in the middle. According to Shaikh, stiffer rears set the natural frequency close to the book value, but I can't replicate his numbers exactly with any other calculator. At the other extreme is Ohlins. In that case, I am failing to account for the progressive nature of the rear spring. If it gets stiffer quickly and is around 400 or more compressed, it could be close to what Shaikh wants to do under heavy load.
the miata DFV shocks come with really soft springs, and i think we started with spec miata spring rates, and went up until the car got slower, and then went back down.
Where did you end up? Back at the DFV rates, back at the Spec rates, or where? Sorry. Not trying to be obtuse. It just isn't clear.
11-10-2015, 09:19 AM
