377Z

iTrader: (1)

The car is a 1991 WS6 T/A convertible. I changed to the Moog 5662 (706#) front and CC635 (??? # variable rate 'cargo coils') rear springs. While I was at it I got new KYB GR2s all around, new ball joints, poly everywhere in the front.

Driving the car gives a slight 'rear end float' feeling like the rear springs are too soft with respect to the fronts. It's annoying. I had debated going to stiffer rear springs or getting airbags and trying different pressures, but since the car has no roof and its a daily cruiser and not a weekend autocross machine I'm leaning more towards changing the fronts for some softer springs. The car has Kenny Brown and Alston connectors, but the car still flexes a bit and hopefully the softer springs would make flex less apparent.

The next lower rated F-body moog spring is the 5610 at 420 lbs/in. Is this going to be a big mismatch with the 36mm sway bar? I'll probably go back to regular (not poly) endlinks to help the situation.

Has anybody used the 36mm sway bar and the 5610's? If not, has anyone added 36mm sway bars on something with softer factory springs (like an RS or a regular 'bird)? This will be my 3rd time playing with this (long story) and I'd like it to be the last.

Thanks

Dewey316

i had 1le bars with my factory RS springs, actualy it made for a nice setup, in some ways i think it was better than ws6 / spohn sway bar combo i have now.

RegaPlanet

Suspension spring specialists sells what rate youll need for a rear spring in whatever height you need also. Eibach does also. You can order them directly I assume or through Ground Control.

Chickenman35

The problem is that the rears are too soft or the rear shocks are too soft. The mistake was getting the Variable rate coils. Initial rate is too soft. You would have been better off with straight rate springs, such as the 5665's... What did you try before?

Why would you want to put soft springs in the frontl...unless you want your front to be " floaty " as well? I would not recommend it at all.

Keep the 5662's. They are a good piece. For rears try the 5665's if you haven't already. They are a straight rate spring. BTW, the spring rating is out of whack in the books on the rears.

Or go to the Auto Wreckers and get some IROC rears. They are more than stiff enough.

Here is a link to a previous discussion on Spring Rates. You may have seen it already.

https://www.thirdgen.org/techbb2/sho...hreadid=200000

One other thought. The KYB shocks are an OK shock...but not a great shock. They are on the soft side. I don't think they are adjustable, but if they are see if you can crank them up a bit. A shock with insufficient dampening , when used with a stiffer spring, can actually give this "floaty" effect. Can't controll the spring oscillations. Can sometimes be hard to figure out which is causing the problem. Spring or shock. I think you may have a little problem with both.

Look into some Koni's for the rear. Sometimes you can get some cleranace items or find a good deal on some slightly used shocks. Autocrossers experiment and change shocks a lot. That would be a good place to start.

Edit: One good way to eliminate this " hunt " through the spring catalogs is to get Ground Controls adjustable height rear spring collars. Them you can go with an actual Racing spring that is stamped and certified true with it's rate. Ground Control supplies Suspension Specialits Springs in their kit at what ever rate you want. I would recommend a 225lb spring.

377Z

iTrader: (1)

I guess I should clarify what I mean when I say its 'floaty.' Its not floaty like a '70's Cadillac where it keeps slowly pitching 4-5 times after a bump or dip. I don't know how to explain it but its just a slight bit more 'give' in the back that is not suited to the stiffness of the fronts and is only felt over certain surfaces at certain speeds. You are basically right--the bottom line is the rear springs are too soft--but only with respect to the fronts as a 'matched' set. IF the fronts were a bit softer and better matched to the rears, I think I'd be happy with the ride. Unfortunately I used the wrong words in my original post--I should have said the fronts are to stiff for the rears, not the rears are too soft for the fronts. Same concept, but gives the wrong impression--sorry.

The key is that the suspension is a matched system and the front 5662 and rear CC635 springs are a poor match in my opinion. To answer the question as to why I want a softer spring--its a combination of a lot of factors--I think its a bit excessively stiff in a convertible (ITS TWISTY). The 5662's are MUCH stiffer than stock than I thought I'd like. Its not that I want to go to a SOFT spring, its just that I want to go to a softER spring than 5662's. 5662's are 706 lbs/in rate according to Moog, from the other post I wonder now what they really are.

A stiff spring will oscillate faster and over a shorter deflection than a softer one, all other factors being equal. Its the slower deflection/rebound of a softer spring over a larger distance that gives the floaty feeling. Other than the relatively minimal force from the gas charge, a shock is strictly a velocity sensitive damper. A shock with insufficient damping can't control the oscillations, but its less apparent in a stiffer sprung car (on the street that is, I don't autoX). Of course, either will not handle up to their potential at the track if insufficiently dampened.

Since they're so inexpensive, I may just try the 5665's to see how they compare, but I wouldn't mind going a bit softer in front and I wonder how the big sway bars will jive with this.

Chickenman35, Nice car by the way.

Chickenman35

Thanks for the compliment on the car.

I know what you mean by a spring mismatch. I managed to mess up my handling balance for Autocross this year by going to a too soft rear spring......I'm having the same sort of "float" from the rear over a bump....but it settles in 1 to 2 oscillations max. 4 to 5 oscillations is entirely excessive. I wonder if you got some defective shocks. As mentioned, the KYB's are known as a soft shock. Softer than the factory AC\Delco BTW.

In may case I know my rears are too soft. I have 5662's in the back and Suspension Specialist's 175lb\in in the rear. They recommended 225's....should' a listened to them I guess


5662's compared to 5664's ( front springs ) are the softer spring. The Moog catalog has the specs backwards. How they rate the springs in the catalog is a bit strange. I always thought that the Load rating that they give is the same as the Racing Industry Standard, " Spring rate " ....it is not apparently. This makes things complicated when trying to sort out springs. It's like trying to compare cam duaration specs...one rated at .050" lift and the other at .006" lift. Hard to figure out.


That's why I'm going to a setup that use proper Racing springs from Afco or Hypercoil. Standard rating systenm and the rate is guaranteed. No more guessing games.

377Z

iTrader: (1)

Dewey316, can I have more info on what your car was/is? i.e. what differed between the two combos?

I'm still confused as to whether or not RS's have softer springs than Z28/TA's.

Also, in what ways was one better than the other (compare/contrast)?

RegaPlanet

I'd assume pretty much any RS other than those badged as RS's but actually police packaged have the "soft ride" suspension. You can actually check what susupension you have by lookign up your RPO codes.

Dewey316

yes, i had the softride springs, with the spohn sway bars. the large sway bars helped control body roll, but it was still a very confortable ride. it didn't change direction as well as what i have now, so it wouldn't do as well auto-x'ing, but for normal canyon carving, it held its own.

laiky

I have what chickenman suggests the 5662/5665 moog combo and i'm liking the rates. I run illuminas also. The only gripe is that the ride height with that combo is dead stock so i'm anxious to start trimming but that can wait till spring time.

laiky

also i paid 105 bucks for the set vs 260 for the eibachs i ditched for them. I'm sorry i ever got the prokit, that said i have a prokit to get rid of!

MFaulkner

Laiky,
What was wrong with the pro kit? Just didn't feel right, poor handling, lots of bottoming out?
Also, Could you post a pic of your car with its new stance. All the thirdgens I see are much below stock height, so I don't have a very good idea of "stock height". Thanks.

laiky

Th Pro kit ws too low and too soft. the car was on the bumpstops all the time. i live in NYC and the roads here suck so that was a factor but i also have a TKO that sits slightly lower than the original T5 and it would bottom out too many times. the progressive nature of the prokit just added to my problems. I would reccomend the 6556/2 combo and tell you to cut them the rates are on par with real performance springs.

I can post a picture if you give me a day or so. it is kind of high but like i said earlier i will be trimming them.

laiky

This is the car with the prokit and 245/45-16 tires

laiky

This the car with the 5665/5662 moog springs and 245/50-16 tires. The springs are uncut.

laiky

oops!

86LG4T56

Hey, I know this is an old topic, but it was really useful for me and I wanted to add some info. NAPA is the only autoparts store I know of that sells Federal Mogul brand stuff, but they change the part numbers and call it NAPA brand. Anyway, the Fed Mogul spring part number 5662 is NAPA part number 2773175. And Fed Mogul spring 5665 is NAPA part number 2773208. And Fed Mogul Spring CC635 is NAPA part number 2775186. Might be helpful.