I have noticed that my car has becoming increasing bouncier after changing only the springs on my RX8. Is anyone else experience this with lowering their car and only changing the springs?

Typical result on any car.

Originally posted by winter
Typical result on any car.

elaborate please

Hi there Kain,

The standard duty shock absorbers are not designed to cope with the increased spring rates of the new springs,
Hence they do not have the damping qualities required to damp the new springs and they also deteriorate really quickly

Cheers

Case

Above is correct, my friend did the same thing with his eco cavalier and its a shi%%y ride in it now. He just replaced the stock with Eibach springs and ruined it.

It looks nice, but doesnt last long

What kind of springs are you using?

Yup, shock compression and rebound damping rates are matched to springs - the OEM shocks are tuned for the OEM shocks. Stiffer shocks require higher damping levels for both compression and rebound - you always need to change shocks when you change springs so that they're tuned to match each other. Changing just shocks can be OK; changing to stiffer springs without changing shocks ALWAYS causes ride and handling problems.

Regards,
Gordon

thanx everyone! so does anyone know of any companies making shocks for the rx-8 now to match with lowering springs? I am asking cause I am not sure if I really want to go all the way to the coilover method? :)

Originally posted by Kain
thanx everyone! so does anyone know of any companies making shocks for the rx-8 now to match with lowering springs? I am asking cause I am not sure if I really want to go all the way to the coilover method? :)

What kind of springs are you using?

Is this true for the RB ones? I had heard that they were designed to work with the stock shocks.

I have TEIN that are waiting to be installed- will wait to find matching shocks now though.......any suggestions?

Are they the H-tech or S-tech?

sorry! TEIN s-tech??? any suggestions? and in advance- thanx

yeah put them on
my car doesnt bounce
yeah ride is not the same of course
and one day (sooner)my shocks will go
but nothing drastic like a bouncing bunny civic,go for it
i dont think there are any companies other than mazdaspped shocks

I was going to suggest the Tein H-tech or Tanabe NF210s. These are both designed to drop the car using the same as factory(roughly) spring rates, which will help in handling and should work fine with the factory shocks.

I have eibach springs and the car still rides great after 5 months

how long until the shocks go out??

My experience in the past is that you need to change the shocks when you change springs, it is never as good as it can be if you don't... Firmer springs require more aggressive damping...

okay, i think we all need a real mechanics opinion on this...

this somewhat pessimistic sentiment i am picking up about installling aftermarket springs just seems a little blown out of proportion....

im thinking that all caution may stem from back not too long ago when cars would just get slammed down...of course then shocks may not last too long...

but take for example, eibach's or even Teins they lower the car a little over an inch, people are making it sound like the shocks will go in 2 years....can we have a real analysis over this?

a valid argument is made the factory shocks are tuned specificially for the factory springs and vice versa...this i think is reasonable to assume, but i doubt if this is an exact science too...everything stock mind you, usually leans towards an average...who is to say Teins springs installed on stock shocks actually would be better for the car?

saying the factory springs always are tuned specifically for stock shocks is like saying the factory tires are tuned specifically for the car...and this is not always the case, its all about whats available and at what cost ----

okay sorry to be long winded but one more example on how factory specs are not an exact science, i also have a CLK 320 2004 which is running on 205/ tire in the front and 225 tire in the back 16"....the car is close to 3800 pounds....these are the factory specs, but after driving this car no one can tell me that this wheel combination is "perfectly balanced" and that a change would not do it justice", to make a long story short Mercedes cheaped out the wheels and these wheels in my opinion are way too narrow for the width and weight of the car....a quick update, news mercedes is going with a larger wheel stock for 2005's...

not all factory specs and balances are perfect for that particular car....there are idiosyncracies in the eight that are not perfect....aftermarket springs may or may not be significantly bad for the factory shocks, i think a lot have to do with the companny that produces that particular spring....

if i am wrong, and aftermarket stuff does ruin my shocks after 2/3/4/5 years then please someone let me know how they know this mechanically, and how they can quantify the extent of which it will...thanks

Originally posted by fietguy
if i am wrong, and aftermarket stuff does ruin my shocks after 2/3/4/5 years then please someone let me know how they know this mechanically, and how they can quantify the extent of which it will...thanks

You're wrong. BUT - there's no such thing as "perfectly matched" to the car - the auto manufacturer's engineers have a set of design goals, for suspension and tires those include ride quality, smoothness, cost, noise, handling balance, responsiveness, grip, durability, etc. Their objectives are an average of what they think the customers of that particular model will want. Not all customers would choose the same compromises that the engineers chose (and, of course, everything is a compromise and a balance of all the factors).

SO - Mazda chose spring rates for the RX-8 standard and sport suspensions (they're not the same springs). I don't know if the shocks are the same, but I'd doubt it. After choosing the desired spring rates, they would have spec'd shocks with appropriate shock and rebound damping rates for THOSE springs, to achieve the desired handling and ride characteristics.

If you just change the springs to stiffer springs - the shock absorber's damping curves will NOT be properly matched to the springs, and you WILL have inadequate damping. The ride will be less well controlled, but to call it "bouncy" would be an exaggeration. The stock shocks with the new springs will not get ruined or blown out much earlier than with the stock springs. They will just be inadequate and poorly matched for their entire life.

How to know this? Lots of experience and lots of reading - there are quite a few good "textbooks" out there with this information. Just go to www.amazon.com and search for "car handling" and you'll see a bunch of hits to start with.

Regards,
Gordon

Originally posted by fietguy
...saying the factory springs always are tuned specifically for stock shocks is like saying the factory tires are tuned specifically for the car...and this is not always the case, its all about whats available and at what cost... No it's not the same thing. Carmakers do spend alot more effort matching springs/shocks/geometry/etc. than with the tires.

---jps

okay thanks for the feedback,

so the aftermarket springs installed will not blow out the shocks significantly earlier than the factory springs would...but the ride will be more unconfortable and inadaquate for the rest of the car's life?

how about the people who have installed aftermarket springs and have concluded the ride is the same? in fact, in this forum, besides the guy who said his ride was bouncy, most people have said their ride is 'feels much like stock' yet with a great reduction in bodyroll in the twisties.

do these people not feel that with their new springs, the dampening is now not adequate?

I've had the Tein H-Tech for about 1000 miles now, and have seen no degredation in handling. If anything, it's better.

I've had my RB springs for about 500 miles now...ride is less forgiving when it comes to bumps (to be expected, I would imagine), but certainly not "bouncier"...to the guy that started the thread, did you get an alignment done after you swapped the springs out?

I just had my Tien s-tech springs installed wednesday. less than an inch off drop in front. less roll on corners

what about aftermarket shocks? I have seen many spring kits for sale, but no shocks. Mazdaspeed is the only one that has been mentioned...

Originally posted by fietguy
...so the aftermarket springs installed will not blow out the shocks significantly earlier than the factory springs would... You never know. That depends on the springs and the shocks. Mazda does put good stuff on their sports cars, so they should do okay....how about the people who have installed aftermarket springs and have concluded the ride is the same? in fact, in this forum, besides the guy who said his ride was bouncy, most people have said their ride is 'feels much like stock' yet with a great reduction in bodyroll in the twisties.

do these people not feel that with their new springs, the dampening is now not adequate? This is what we call the "butt-dyno". Just like with little engine mods, the ability to "feel" the difference is a little iffy. Mind you, when you are talking about ride and feedback, then feel is everything, so that's pretty easy to determine via the "butt dyno". And for the most part, aftermarket springs aren't so different from RX8 springs (which are going to already be stiffer than your standard American sedan and some American "sports" cars), so there will be little "bouncing" effect that you can sense. Most of these springs won't be so mismatched that this will happen.

For actual handling, braking, and accelerating performance, remember that the goal is to keep that optimim tire contact patch, and keep it consistently. If you change springs, and the new spring/shock combination is not as well matched, you won't keep that patch as consistently. That's a fact. The question is how much of a difference is that going to be.

Now, is it going to be so different that a driver can tell a difference? Probably not. And when you are putting on most of these springs, you are lowering the car. The simple matter of dropping the COG an inch or more will make a significant difference in the handling and roll, even if the new springs aren't stiffer. And that improvement in handling will normally be much greater than the decrease in the optimum tire contact patch. It's that low center of gravity that really makes a difference in how nimble a car is.

My point is, even though you won't have perfectly matched shocks/springs, you will still improve handling by installing most aftermarket springs. It's just that it will be even better when you can match the shocks and springs.

On a side note, this is one of the ways that a coilover setup is better than most aftermarket spring/shock combinations. It is very hard for someone to match a set of springs and shocks from different companies on their car. I know a little bit about suspensions, more than the average Joe, but I know that even if I had a chance to test all sorts of combinations of springs and shocks, I would have a heck of a time finding the optimum combination. With coilovers, they are already matched by people who have the equipment and knowledge, and they've already done the work for me. Now, if you can get a package of springs/shocks from a company that are already matched (like the set from Mazdaspeed), then you're ahead of the game there too.

---jps

From an engineering standpoint, my opinion is that changing out the springs without installing properly matched shocks could possibly shorten the life of the OEM shocks. However, all anyone can do is speculate or call upon past experience without knowing the design specifications (fatigue life, rated dynamic load, etc.) of the OEM shocks. It's very possible that the shocks will be just fine with stiffer springs, but it's also possible that life could be severely shortened.


Manufacturers specify damping rates for the shocks to achieve the desired damping ratio for the bounce mode of the vehicle. This is the dominant mode of vibration response when a vehicle goes over any sharp discontinuity in the road surface. The higher the damping ratio, the more rapidly the bouncing mode decays, and vice versa. A very rapid decay of bounce feels harsh, however it is better for handling. For this reason, sports cars are tuned with higher damping ratios than luxury vehicles.

If you consider the vehicle sprung mass and springs as a mechanical oscillator, the damping ratio, which I'll call Zeta, can be written as follows:

Zeta = c / (2 * (k * m)^0.5)

where c = shock damping coefficient, k = spring rate, m = sprung vehicle mass.

It's obvious that with a stiffer spring (higher k), the damping ratio decreases, and a lower damping ratio means that the vehicle will oscillate or bounce more. Therefore, there is no doubt that with stiffer springs, the OEM shocks will experience more cycles in a shorter amount of time. And since the durability of suspension components is measured with fatigue life, or number of cycles until failure, it is logical to conclude that the shocks will fail in a shorter amount of time.

The only question is how robust are the OEM shocks? Will the life of the shocks decrease on average by 1 year? 2 years? or more? We'd have to get some input from the Mazda suspension engineers to answer these questions.

thanks members, the last two answers were brilliant...and puts into perspective many assumptions

the missing factor just seems to be how robust the OEM shocks are...

hmmm, $150 for springs, $2000 for coilovers....if we get the coilover setup how do we know as consumers its the right dampening set up for the car? will coilovers life span be shorter or longer than OEM?

great responses sputnik and buckeye.

Sptunik: based on ur last statement which would you think is the better option to go with..

JIC Coilover or MazdaSpeed Spring/Shock Setup.

I am not looking to just drop the car for looks, I would like to get rid of the bodyroll when autox.

also for those AutoX experts will changing springs and shocks change my class from BStock?

It sounds like a cop-out, but it depends on who we are talking about.

First, I don't know about JIC themselves. I'd have to look at the different coilover setups available for the car, and see how they were put together, and how stiff the spring package is. There are some companies that make good coilovers for one make/model, and not-so-well-thought-out for others.

Second, it would also depend on how much suspension travel you lose with just the spring/shock setup. Even on relatively smooth surfaces, you do need to keep some suspension travel (for ride, handling, accelerating, and braking), and alot of aftermarket spring/shock packages have you either bouncing off the bump-stops, or setting the shocks too stiff (some people also adjust their coilovers too stiff too). I would look into it, but I expect that the Mazdaspeed setup will be okay in this aspect.

Third, if you are planning to go as far as coilovers, you have to plan on changing other suspension components to get the most out of it. You will need to consider replacing all of the suspension bushings, swaybars, upper shock mounts, adding effective strut tower bars (not just shiny pieces that go from tower to tower, solid bars that also connect to the firewall). At this point, lightweight wheels become a major factor, and even replacing the brake hardware with lighter calipers and two-piece rotors (even if you do not increase braking effort) makes a difference. Otherwise, you won't get that much more of a benefit from installing coilovers over mere spring/shocks. You don't have to do it all at once, but you need to eventually to get all of the benefits of a coilover package.

So in short, if you're just looking for a basic upgrade, the MS spring shocks would be the best bet. It would only be worth getting a full coilover package if you plan on doing the other mods too.

And I'm not an SCCA rule expert, but I do know that springs will put you into Street Prepared. Shocks might be considered "consumable" items like rotors and brake pads, and could be changed, but I could be completely wrong on that.

---jps

I disagree. I think you will get plenty of advantage with a set of matched coilovers. The ability to independently set height of the car is very valuable - you can choose the ride height that matches your roads & driving style (the value of suspension travel should never be underestimated). Additionally, the ability to change the amount of damping can be easily utilized if you autocross - nice & stiff while competing, and nice & comfy while commuting. While the other things you list certainly go into making a top-notch car, I'd say you can extract the majority of the potential benefit of a set of coilovers simply by installing them, choosing a good combination of ride height & alignment settings, and installing a set of sticky tires (say, 245 section Kumho MX).

Another nice benefit of the stiffer springs is that they reduce body roll without the use of stiff sways. I know there is much controversy on this, but after fiddling with my Miata for 5 years I've come around to the idea that, for sways anyway, the smaller the better (with stiff springs, anyway). I'm still watching the market, but for my RX-8 anyway, I think the car will be best served by a nice set of coilovers with about a 50% increase in (linear) spring rate, a broad range of damping adjustment, a moderate height reduction (at my discretion, of course), and stock sways. Yes, this does sound a bit like the MS setup, with the exception of ride height & damping adjustments. I really want those.

And yes, non-stock springs, or spring mounting methods, bounce you out of B stock (but shocks do not). Just run STU instead - no reason to run SP, unless you really want to run R-compound tires, in which case you end up in ASP (good luck).

George

Correct me if I'm wrong here. My region has no STU class, so with my only mods being a cat back, springs, and a front sway, I should be running ASP, yes? I did my first event a week ago and got classed in SM (that was without the sway as well). Didn't seem right to me, but I didn't know enough at the time to say anything. I do plan on getting a dedicated set of auto-x wheels, and probably will slap R-compound tires on them. Save a little wear and tear on the lovely RE040's.

Yes, with those mods you are legal in ASP. Funny they put you in SM, the RX-8 is technically in SM2.

And you may want to petition your local region to allow STU. Show up at a commitee meeting and ask - usually they will add it without much fanfare. Of course, if you are the only person in the class, it's not much fun, but then again it's not much fun in SP unless there are several other "under-prepared" cars in your class to compete with ("real" SP cars are very fast). The nice thing about STU is you get a better PAX factor, so you'll place higher overall, and you can buy a special set of street tires, which will last longer than Kumohs or Hoosiers.

Originally posted by GeorgeH
I disagree. I think you will get plenty of advantage with a set of matched coilovers. The ability to independently set height of the car is very valuable - you can choose the ride height that matches your roads & driving style (the value of suspension travel should never be underestimated). Additionally, the ability to change the amount of damping can be easily utilized if you autocross - nice & stiff while competing, and nice & comfy while commuting. While the other things you list certainly go into making a top-notch car, I'd say you can extract the majority of the potential benefit of a set of coilovers simply by installing them, choosing a good combination of ride height & alignment settings, and installing a set of sticky tires (say, 245 section Kumho MX)... It's hard to argue with that. I think it really boils down to how you plan on using the car.

---jps

I wanted to add that unlike many other cars I've had the RX-8 with stock suspension is already on the verge of being "bouncy".

I personally would not do any spring swap without doing the shocks as well.

That is my opinion and it is based on doing spring upgrades on my last two cars. I do not have any actual experience with this on the RX-8 and I don't plan too for another few years. When my factory shocks wear out, I'll do something then.

-Mr. Wigggles

SHOCKA, if you change the springs then you will be moved out of stock B, if you do just shocks you are fine.

SHOCKA, if you change the springs then you will be moved out of stock B, if you do just shocks you are fine.

Originally posted by GeorgeH
Yes, with those mods you are legal in ASP. Funny they put you in SM, the RX-8 is technically in SM2.

And you may want to petition your local region to allow STU. Show up at a commitee meeting and ask - usually they will add it without much fanfare. Of course, if you are the only person in the class, it's not much fun, but then again it's not much fun in SP unless there are several other "under-prepared" cars in your class to compete with ("real" SP cars are very fast). The nice thing about STU is you get a better PAX factor, so you'll place higher overall, and you can buy a special set of street tires, which will last longer than Kumohs or Hoosiers.

According to this site here (http://www.scca-milwaukee.org/Solo/2004/CarClass2004.pdf) the RX-8 runs in BSP. Just for info.

i have had my tein s techs installed for several hundred miles with no complaints. as far as hurting the oe strut life well if they lasted 2yrs i would think that would be plenty even if i didnt change the springs.

as for a coilover setup im waiting on the flex system and edfc from tein to come in and match them with tanabe front and rear sways. ive installed the flex and edfc on a sti and it was unbelievable how they felt. stock the sti comes with a 39mm shaft in the strut and they ride wonderfully.

in my opinion, anyone who worries about hurting the oe struts by puttin aftermarket springs in should either save up and buy the coilover setup or just leave it alone.