apsolus

iTrader: (2)

i have an 89 vert with almost 300,000 miles on it, just short. front suspension was gone, all of it. so i replaced everything up front.
i installed
mazda speed lower control arm bushings,
racing beat front sway bar,
racing beat sway bar endlinks,
rebuilt steering rack,
inner and outer tie rods
front wheel bearings
front brakes
and i decided why not try coil overs... and this is where my issue lies.

i purchased these coil overs from buyautoparts.com. description stated a perfect fit for my car, specifically my car. well they did bolt up but they are punishing me when whiplash and moments being airborne. way to much spring IMHO. they are size 10 in the front and 8 in the back. thats the last number on the part number on the spring itself. i am told stock is just 8 in front and 6 in the rear.

im trying to make sure i havent just set them up wrong.
i have the preload all the way out so the spring can actually move around in the coil over and full droop.
by the way, wheels hardly move down when lifting the car off the ground. i got the adjuster screw for the shocks all the way to there weakest setting.
its cool that i can make the wheel go under my wheel well, but at the cost of all your ride quality? i hope im making sence! please help!! btw i got the kit labelled it was for the street!

ZDan

Cheap coilovers suck. bad. always.
What exactly are they? "these coilovers from buyautoparts.com" doesn't say much!
What did you have for springs/dampers before? Stock? Were they OK? You might just swap them back in.

Budget coilovers are guaranteed to have absolute ***** for damping. Too stiff for bumps/potholes and too soft for handling. Poor damping will kill ride and handling regardless of the condition of the rest of the suspension.

Howard Coleman

iTrader: (6)

sorry to hear.

check your tire pressure. 30 front 27 rear set cold

howard

apsolus

iTrader: (2)

just seems like false advertising though. they say its a street kit. how can they say that? its horrible on the street, there are times i have only 3 or 2 or no wheels on the ground. i have lifted the suspension and that seems to be helping but like i said i have spring preload all teh way out. are there any suspension techs out there that can help? i dont wanna have to deal with returning and all the down time ect.

apsolus

iTrader: (2)

i have low profile 17s on my car i dont think tire pressure like that would work, would it?

gracer7-rx7

iTrader: (16)

You get what you pay for... Good shocks are not cheap for a reason.

apsolus

iTrader: (2)

wow its pretty easy to rip off the average joe. im hoping someone will chime in with good news.

Jaiyurai

iTrader: (30)

What type of ride did you expect with coilovers? Most, if not all, coilovers are much much stiffer ride quality that OEM and most strut/spring suspension kits. Even worse, you went with a cheap brand coilover kit that likely has little to no R&D in shock dampening.

Sounds to me that you should have better spent the money on a proven setup like KYB AGXs and eibach/tanabe/swift springs.

But if you're adamant about not returning them, then I'd recommend getting the suspension tuned and car aligned but a reputable garage. If the ride quality is still too stiff for you, then possibly ordering 8k/6k spring rates and switching them out with your 10k/8k set.

misterstyx69

iTrader: (142)

I went through 2 sets of coil overs and I right now I just drive on the street.
I couldn't stand the ride and sold them.
I did find that the spring rates were too high and I bought a softer spring set which did help,but I didn't need coilovers for just driving downtown,etc.
I bought KYB AGX's and Honestly I like em.

silverfdturbo6port

iTrader: (26)

you def get what you pay for

Mahjik

iTrader: (1)

This will also hurt your ride quality. The less sidewall you have, the more the road vibrations are transmitted to the chassis. You really need to decide what is your priority with the car, form or function?

ZDan

I think the stock spring rates should be a LOT lower than that, probably more in the 2 kg/mm range (~100 lb/in) according to a quick search I did.

But most of the harshness you're feeling is from the damping. Unfortunately if you already have the adjusters screwed all the way out and it's still to harsh, you're kinda stuck...

High-end dampers can bleed off flow at high velocities to smooth harshness over bumps and potholes. Budget dampers will not be able to bleed off damping and hence will act as if they're locked solid when you hit a bump.

There's really no fixing it, the dampers are just budget dampers acting like budget dampers.
You might consider swapping the stock springs back in and getting new shocks, and either trying to return the coilovers or sell them.

FWIW, we replaced all the (blown) shocks/struts in my wife's '05 Mazda3 with stock-replacement non-adjustable KYB last year, and I'm *seriously* impressed with them. Very firm in cornering/braking, but very compliant over bumps/potholes. Tire Rack shows a few different KYB stock-replacement struts/shocks for the FC, and also Bilstein, a *very* reputable brand:
http://www.tirerack.com/suspension/S...9&autoModClar=

And if you want slightly stiffer-than-stock springs (instead of many times stiffer), you could go with these Racing Beat springs, only 20% stiffer. But IMO you might just stick with stock springs if you're not tracking/autoXing seriously.
http://www.rx7store.net/product_p/rbspringsfc.htm

It's not the tires or anything else that's giving you grief. It's the damping in those budget coilovers. Only way to fix it is to get rid of them and put something decent in there.

apsolus

iTrader: (2)

thank you.

i honestly had no idea what i was buying then. i figured sence i had a completely blown front end including the struts top to bottom id get the coil overs because they came with everthing i already needed to replace anyway. street kit HA! guess i was just plain ignorant. oh well this wont be impossible to fix but what if i was low on cash right now? i hope they take these things back. i mean the car is hardly drivable and forgive me but when suspension is labelled as street kit i figured it would be drivable.....

Tem120

iTrader: (5)

It seems to be the rumor out there that coilovers will give a better ride then shocks with soft springs .

Now as for your predicament . You may be able to purchase softer springs for the setup that may help reduce the bounciness But like stated above we would need to know the brand of the shocks / coilovers and any info you have and


Also.... According to this https://www.rx7club.com/2nd-generati...-setup-958464/

stock FC shock rates are 95f / 90 R spring rates ... which equate to about 1.6 KG so running 10kg / 8 kg yeah.... thats over 6 times as stiff . and if the shocks are made to match those settings ... so ofcourse they will be stiff . LOL

This is why its so important to do your research and not blindly trust companies out there . Only thing I can suggest is try and get a refund , and buy stock replacements if you want your nice soft ride back



1 (kg / mm) = 55.9974146 pounds / in
2 (kg / mm) = 111.994829 pounds / in
3 (kg / mm) = 167.992244 pounds / in
4 (kg / mm) = 223.989658 pounds / in
5 (kg / mm) = 279.987073 pounds / in
6 (kg / mm) = 335.984488 pounds / in
7 (kg / mm) = 391.981902 pounds / in
8 (kg / mm) = 447.979317 pounds / in
9 (kg / mm) = 503.976731 pounds / in
10 (kg / mm) = 559.974146 pounds / in
11 (kg / mm) = 615.971561 pounds / in
12 (kg / mm) = 671.968975 pounds / in
13 (kg / mm) = 727.966390 pounds / in
14 (kg / mm) = 783.963804 pounds / in

Tem120

iTrader: (5)

ALSO , springs dont usually go bad . so you can normally reuse them .

so all you really needed to do was swap out the shocks for some fresh ones

ZDan

I went from 9kg/7kg Tein SS coilovers on the FD to 11kg/11kg Ohlins DFV, and the ride went from intolerable on the street (was considering unloading the car) to being an absolute dream.

DAMPING (whether shocks or coilover dampers) is infinitely more important than SPRING RATE as far as ride tolerability over bumps and potholes goes.

That said, very stiff springs with very good dampers will feel more "busy" as the natural frequency will be higher. But impact harshness will keep the ride smooove over road irregularities.

Softer springs won't fix it. ***** dampers => ***** ride. They aren't bleeding off flow at higher shock speeds, softer springs may paradoxically make the harshness worse!

You should FEEL how smooth the Ohlins DFV dampers valved for 11kg springs are over bumps!

But I do agree that for a street car, 6x factory stiffness (I thought stock was stiff enough for street-only usage in my '90 convertible, and I'm a track guy) is not the best idea....

STILL, the impact harshness is 100% due to the cheap dampers.

KYB or Bilstein replacement dampers with factory springs or the Racing Beat 20% stiffer-than-stock springs should be a huge improvement and return the car's feel to what it's supposed to be.

I miss my '90 convertible :'(

cryomark

ZDan is right about the damping having a much greater influence than the springs. I have the Ohlins DFV setup with 17k/13.5k springs. Still a dream on the road.

I don't think 10k/8k is your problem.

Please state the brand and model of your kit and maybe someone can help you with the setup here.

Mark

Howard Coleman

iTrader: (6)

there seems to be a lot of comparing apples to oranges on this thread.

the OP's chassis is an FC not an FD.

the FC has a macpherson strut suspension NOT a double A arm.

as such, the spring and shock align with the center (laterally) of the tire.

therefore the Spring Rate is the Wheel Rate.

the FD has a proper double A arm setup designed to provide racing type camber gain on bump. the FC strut provides no camber gain so 3 degrees body roll in a corner generates 3 degrees of camber loss V static.

the FD double A arm locates the spring/shock (there are no struts on an FD) significantly inboard of the tire center.

this means the FD spring rate and wheel rate are (very) different.

stated simply...

a 10 KG front spring on an FC means 10 KG at the wheel (wheel rate)

a 10 KG front spring on an FD produces a 6.05 KG at the wheel (wheel rate)

BIG DIFFERENCE.

so the 10 KG springs on the OP's FC equate to having a 16.5 KG spring on an FD.

a 16.5 KG spring is 935 pounds per inch!

the corner weight on an FD is 710 pounds.

max wheel travel would be 3/4 of an inch. sounds like a fun drive.

that is assuming the "10" refers to KG rate.

there is nothing mystical about springs... they balance against load. super stiff is not fast, it is the travel that talks to you telling you where the limit is. the less travel the less warning.

do keep in mind that a rate cumulates. a 600 pound per inch spring offers 600 pounds of resistance at one inch and 1200 pounds at two inches. 1800 at 3.

that all said, shocks, if too stiff can take a proper ride to the point where your fillings start to fall out. shocks should generally be matched to the spring rates.

finally, the FC has a flexible chassis compared to the FD. put real stiff springs on it and the chassis just flexes.

HC

ZDan

I don't think anyone missed that, I certainly didn't mean to imply that spring rates should be similar between the two.

Relative contributions of spring rate and damping still apply. Stiffer springs with fantastic damping will feel a lot more agreeable over unimproved roads than softer springs with crap damping, that's true for any car.

But his rates are still insanely high for a street FC, which I think we all agree. WITH the understanding that spring rates make for very different wheel rates on the FC vs. the FD.

There is usually an offset (scrub radius) between the strut axis and the center of the tire at the ground. Also the strut is angled quite a bit inward and aft from the wheel/tire. Motion ratio is *closer* to 1, but usually in the 0.9-0.95 range. Since motion ratio is squared to get wheel rate from spring rate, even 0.95 gives a 0.90 factor to get wheel rate from spring rate.

Struts usually *do* give more negative camber with bump travel. On the order of 0.5degrees per inch of travel initially. Camber gain will fall off with travel, but to get to the point where you no longer gain negative camber you have to go so far into bump that the control arm is perpendicular to the strut angle, usually ~15 degrees PAST horizontal, often way beyond practical travel limits.

That said, I'm not familiar with the FC's struts geometry, but for sure lowering an S30 Z an inch gives you about .5 degrees or more negative camber.

Probably closer to 8-9kg, but yeah, mighty damn stiff...

It's an even bigger difference than that! FD motion ratios are about 0.62 front, 0.70 rear, right? So with 10kg/mm springs, front wheel rate would be 10*(.62)^2 = 3.84kg/mm wheel rate.

FC with the same spring rate has more than 2x the front wheel rate. (.925/0.62)^2 = 2.23x
(*****uming .925 motion ratio for the moment!)

Of course basic damping should be matched to the spring rates, but on top of that decent dampers will be digressive and bleed off in high-velocity impacts which makes the ride more tolerable and improves traction over rough surfaces. Cheap dampers, even if the low-speed damping is "right" for the spring rate, will generally give way way too much high-speed damping.

They often compensate for this a bit, so you end up with way too little low-speed damping and way too much high speed damping!

The OP clearly got the wrong coilovers, and IMO should just get good quality replacement dampers and maybe known good aftermarket springs and he should find happiness again.

Cheap coilovers give a sucky ride even if the spring rates are semi-reasonable.

But yeah, running the numbers shows just how RIDICULOUSLY stiff 10kg springs are for a street FC!