Springs / Rates for Coilover kit

[Whizbang]

i have an 82 FB setup with the GSLSE suspension. Currently i have some adjustable struts and eibach springs, but want to upgrade to the coilover kit you offer.

The only question i have is the spring length and rate. I am assuming that th shorter the spring length the lower the car sits. What is the norm for length? 7 or 8 inch? Then comes the rates, what exactly would you recommend rate wise? I am moving to colorado so the roads are smooth (and fun). The car falls under toy status and generally speaking my tolerances of harshness on the street are pretty high.

I was thinking about the 2.5"x7" in a 425 to 450 rate front (mostly because i plan on running the heavier 13b and possible turbo components in the future) and getting the kit also for the rear and run with a rear 200.

I currently have ST sway bars, stock otherwise. Im figuring camber plates would also be a good upgrade? Would i need them upon install of the above setup?

[Rogue_Wulff]

The rates you list for the front, are probably a bit over the top. I have 350F/200R, and the ride is firm, but not harsh. I actually like the ride quality, as it's only marginally firmer than before, when I had the ST springs.
My setup uses 7" x 2.5" Eibach front springs, so I would venture a guess that 7" springs are plenty long enough. Any longer spring would require lowering the bottom perch further, and wouldn't be of any real benefit.
With 7" springs, and a 4" threaded collar, I chose 5" from the top as a spring perch location. This will allow me to adjust from stock hiegth (or higher), to ~3.5" lower than stock. The latter setting will not allow much travel before the strut bottoms out internally.
The location I chose for the spring perch also prevented he need to relocate the brake hose bracket on the strut housing. Going any lower would have required lowering the bracket as well. This was on S2 strut housings, I don't know if SE housings have a different brake hose bracket location. The SE housings that came with my coilover parts have had the bracket relocated, and the lower perch was 5.5" from the top of the housing. I may use these on my SE, which is destined to become a primarily track use car. I doubt I would daily drive an SE with RB intake and edelbrock 600, in a fairly stripped out car, when I have the GS with AC and cruise.

[Whizbang]

Would the increase in weight from the heavier 13b cause a need for a slighter heighter spring rate?

[Rogue_Wulff]

I wouldn't think the extra weight of a 13B would really need a stiffer spring. It's not that much different in weight from a 12A. Especially considering I still have a fully functioning AC on the car.
You also have to take into account the struts. Having adjustable struts also affects how the spring rates will alter the ride characteristics of the car. You can stiffen a softer spring by stiffening the strut. It's kinda hard to soften a too-stiff spring. Aftermarket swaybars also factor in here, since the front is almost always much larger than stock.
The idea is to create a suspension setup that will work well together, without destroying the ride quality on a car that will see street use. Overly stiff suspension only works well on a very smooth track. The rest of the time, it's more of a nuisance than anything. Few streets are really smooth enough for an overly stiff suspension to work well.

[Whizbang]

hmm...so ill probably just opt for the setup you seem to be having good experience with and see what happens from there.

I also was looking at the other items RE Speed sells, including the sphereical kits. Any thoughts?

[Rogue_Wulff]

For a street car, forget the spherical stuff. The lack of rubber to isolate the bumps will have you regretting the installation of spherical bearings.
For a track car, they're great.

The spring rates I have are probably about the upper limit for a street driven FB, given the prevailing road conditions in Ok, so your experience may vary.
The car can feel a little twitchy on the rougher sections of the twisties, but is great most of the time.
I don't have aftermarket sways, and I only have KYB GR2 struts/shocks. Both of these are factors in how my car rides/handles. I don't have camber plates, either.

[Whizbang]

hmm...seeing your now my unoffical expert.

I was also reading about the "roll center blocks". Didnt really explain well enough to me as to why i would want them and how they effect the ride and if they are worth their fiscal merit.

Aside from that would just getting a good poly bushing set as opposed to the spherical bearings stuffs be a good idea?

Should i guess that the low control arm kit (the replacement rod end piece) is basically not worth while either?

[Rogue_Wulff]

The roll center blocks correct for loss of suspension geometery on cars that are lowered by more than 1.5-2". When a car is lowered that far, the pivot point in the ball joint can actually be higher than the control arm bushing. This is detrimental to handling.
If you are going no more than the normal 1-1.5" drop in the front, they really aren't needed. Especially on the street. If you plan to run SCCA CSP autox, they're not allowed.
Poly bushings up front, and in the lower rear arms, are worth the investment, particularly if your current rubber bushings are in need of replacement. Do not put poly bushings in the rear upper arms. Bad karma.... The current bushings are probably due for replacement, unless they are less than 5 years old.
As for the rod end mod on the stay rod, I wouldn't do it on a street car. I cannot recall if this is an allowed mod for SCCA CSP. I don't *think* it is, but wouldn't put money on it. I'm pretty sure none of the spherical bearing's are legal in CSP, aside from possibly the stay rod.

Again, all of these are my opinions, based on a street driven car. A car that will only see track use is totally different. My buddy has a track-only FB, and it has all of the listed mods.

[bwaits]

Again, all of these are my opinions, based on a street driven car. A car that will only see track use is totally different. My buddy has a track-only FB, and it has all of the listed mods.

Wow......I need to set you up with the password to the ReSpeed technical email address. :)


Aside from that would just getting a good poly bushing set as opposed to the spherical bearings stuffs be a good idea? Should i guess that the low control arm kit (the replacement rod end piece) is basically not worth while either?

All very good advice above. To get a bit deeper in depth on the rates: The spring rates can not be to high or the shocks will not control them. The standard off the shelf shocks sold for the first gen are good for about 350# up front. You really do not need rates higher than that. We have tried all the way up to 500# on the front and settle on 375#-425# with the use of custom valved Bilstien inserts for the IT car.

Metal to metal pivot points (As in Spherical) are harsh for the street. The major down side is the dirt and grime. They need to be kept very clean or the grime starts to score the metal. Once that starts you have slop in the sphericals. Once you have slop they get louder and sloppier. Best to stick with poly for the street.

Our delrin stay rods are great for the street.

Roll center blocks go between the steering arm and the strut housing. They basically move the outer pivot point (Ball Joint) down the compensate for the inner pivot (LCA to crossmember) being moved down during lowering.

Spring length standards are 8" for the race kit and 7" for the street kit.

-billy

[Whizbang]

alright so i should going forward with getting the coilovers here come spring.

it says the street coilovers cant handle more than a 250 lb spring but you mention 350 up front. So did you run the road race kit?

[bwaits]

Street Kit = 7" Spring, 250# max
Race Kit = 8" or 10" spring, any spring rate

-billy

[FIBREMAZ 13 BEEF]

My vote for spring rate would go to 350Lb, been running this rate for a while and very happy with the handling and ride

[Whizbang]

so ill opt for the road race kit then.

[Rogue_Wulff]

alright so i should going forward with getting the coilovers here come spring.

it says the street coilovers cant handle more than a 250 lb spring but you mention 350 up front. So did you run the road race kit?

Yeah, I'm running 350# front springs on my coilover setup, but my setup came from GC, it's very similar to the road race kit from billy. I was planning to buy the RR kit from billy, but found a deal (WAY) too good to pass up on the GC stuff.
The minor welding required to install the RR coilover kit is pretty simple to do. I did the full conversion, including swapping rear springs, in less than 3 hours.

[Whizbang]

looks like a good way to go. once i finish the rx8 transmission swap install its my next step. Cars are such a never ending project.

[Rogue_Wulff]

Cars are such a never ending project.
True enough.

FWIW, I attended an autox drivers school last weekend, and the instructor was quite impressed with the ride/handling of my car. He couldn't recall the rates, but knew I had gone with a custom setup.
His only comment towards improvement, concerned the soft dampers. Coming from someone with National level skill in a Miata, I take his word pretty well at face value.

[Whizbang]

we do have to work with a limited after market sadly. What dampers are you currently using

[Rogue_Wulff]

KYB GR-2's. They came installed on the car.
Soon to be replaced with Illumina's (from billy, of course).

[Whizbang]

i have illuminas up front currently then regular tokicos in the rear.

[Rogue_Wulff]

Any idea of what you're going to use on the rear for springs?

[Whizbang]

im thinking about shooting for a 200lb spring to start with and see how that works out. Mostly just shooting at the dark.

[Kentetsu]

Wow, I can't believe I missed this entire conversation! :)

All good information here, but I just want to point out another option when considering your spring rates. Rather than going with high spring rates when I assembled my suspension, I went a bit softer (275/150) and made up the difference with swaybars.

My thinking in this is that the softer spring rates allow for a bit more compliance in keeping the rubber attached to the road. Too high of a spring rate, and you can get the same effect as a rock being skipped across a pond (the spring is so stiff, that the car can't absorb enough of the little bumps to keep the rubber on the pavement). I have actually seen this happening with a fellow competitor's RX7 that uses 450 Lb. springs on the front (not sure of the rear rate).

So, using a softer spring can make the car "stickier" and give higher traction. But softer springs will also cause more body roll, right? Well, that's where the swaybars come in. Running stiffer swaybars keeps the body roll to a minimum, without causing a (noticeable) increase in ride stiffness.

This setup has brought me great success in autocrossing in CSP, to the point that I am now beating the Miatas consistently (even those on race rubber Vs. my Sumitomos). And, even better, the car is perfectly capable of being driven daily on the streets. I even made the 800 mile trek down to Deals Gap last spring, quite comfortably.

So, there seems to be two basic opinions concerning spring rates. One is to go very high on spring rates, and sometimes even removing the swaybars altogether. The other way (like mine) is to go softer on the springs, and heavier on the swaybars.

I am very happy with the path I chose, and the car has been a real monster at the races. Anyway, I just thought I'd throw that out there for you to consider. Hope this helps. :)



.

[josh18_2k]

problem with sway bars is they are a non linear spring (rate depends on roll) so its harder for a damper to properly control the spring/sway combo. ideal damping at full lean will be underdamped at anything less

soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling

my local suspension guru chris billings swears by choosing springs for roll/pitch/dive/etc, and using ONLY a front bar to balance the car mid-corner

[Whizbang]

will the hill climb seasons coming up, i might just have to run what i have due to fiscal constraints and see how she handles as is and work from there. Find out what it wants.

[Kentetsu]

problem with sway bars is they are a non linear spring (rate depends on roll) so its harder for a damper to properly control the spring/sway combo. ideal damping at full lean will be underdamped at anything less

soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling

my local suspension guru chris billings swears by choosing springs for roll/pitch/dive/etc, and using ONLY a front bar to balance the car mid-corner

You have to remember what the other end of the swaybar is connected to (yet another spring/damper combination).

"soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling". Absolutely not true, if combined with good swaybars.

Anyway, I am not going to start an argument in this thread. As I have said, there are two schools of thought on this matter. I am of one, you are obviously of another.

But while you are here, why don't you take a look at this video. Maybe then you will consider that there might just be a slim possibility that maybe, potentially, I really do have a point. :)


http://www.youtube.com/watch?v=rWpEYAKo0fU

[Rogue_Wulff]

"soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling". Absolutely not true, if combined with good swaybars.



The swaybars have no effect at all under accel/decell conditions, regardless of whether they are 1/8" or 5" dia. Spring rate and dampers are the only things that have any effect on dive/squat, aside from geometery.... Springs determine how far it goes, and dampers determine how fast it gets there.

Otherwise, you do have a valid point. Softer springs can be benefitial on rougher courses. Can go fast with the tires dribbling......
A wise man once said to me "Stiffer springs and swaybars will usually make a car faster, but harder to drive". Of course, he was refering to handling, not straight line speed. It was during an autox/road racing suspension seminar......
He also said to use springs to adjust the car, and swaybars to fine tune the springs.

[Kentetsu]

You are correct RW, I mistated that (was thinking roll, as opposed to dive). Still, not a problem with my car. Maybe it has to do with the ride height? Or maybe the Illuminas?

"He also said to use springs to adjust the car, and swaybars to fine tune the springs."

I have read that in some books as well, but like I said, it did not strike me as the way to go (especially while trying to preserve the daily driveability of the car). My goal is to get the absolute best handling, while still being able to comfortably drive the car to work every day.

A fellow competitor with a RX7 did have the 450 Lb. springs on the front, and when the car was later up for sale he freely admitted that it was not driveable on the streets with those springs on it. That is definitely not the state I want to end up in. :)

[Rogue_Wulff]

450 is a bit too high for a 1st gen on the street. In fact, too high for "drop-in" strut cartridges to handle without premature failure due to internal heating.