Thanks, gc. Edited:

Perhaps I missed the answer, but after searching I found no confirmation about IROC spring rates. Moog offers 5662 (748) and 5665 (107). Spohn offers "IROC Style" replacements (649 and 107), but are those rates consistent with OEM? EDIT: note the correction for Spohn's springs at the bottom.

Slim, Eaton has IROC springs as well, at $300 a set. I'm cheap.

Here's Moog:

Untitled

JamesC

 

Im not sure about those, but when i got new springs i called Eaton Detroit and they had what they said were exact replacements for the Z28 springs i needed.

 

Moog 5662 @ 706lb is for IROC hardtop w/o a/c
Moog 5664 @ 767lb is for IROC convert or hardtop with a/c

This is what my cross ref shows.

 

Did you get their springs rates though?

 

I tried to verify the rates, but didn't get any useful info from Detroit. By the way, I found this note in quarantine from tech@spohn.net: They're the same spring rate [the IROC style] as factory IROC springs.

JamesC

 

Many online sources have the 5662 and 5664 spring rates reversed. One catalog had it bass-ackwards, and the info spread. Remember 5664 is the stiffer one (info in this thread is correct).
5660 I think is the sport coupe/RS replacement spring.

649lbs/in would be somewhat soft, I think that's the 5660 spring. You know that the 5665 is the rear straight rate spring, vs the cc635 cargo coil. I think the cc spring is more commonly listed as the factory replacement spring.

 

I've done some searching since yesterday, but I've found no real confirmation, I guess, of what the OEM IROC spring rates are. From Rock Auto:

Husky RC 5662: Front Coil Spring w/AC with auto or manuel: IROC.
Husky RC 5665: Rear Regular Coil Spring
Moog 5565: Rear Suspension, Regular.

In my search, I've found that both the 5665 and the cc635 are both listed as IROC replacements.

More personal confusion here:

https://www.thirdgen.org/forums/susp...g-swaybar.html

Here's a spring rate calculator. Can any one provide the info:

Calculator - Chassis

JamesC

 

James I can't confirm spring rates but I swapped in the Moog springs that you listed a few months ago. The Moog 5662 front springs looked identical to my WS6 springs(tagged BZW) both in the # of coils and height. Once installed the ride height was identical as well so I guess the originals were still in good shape . The Moog 5665 rear springs were different in appearance from the stock rear WS6 springs(tagged NNL). The Moog's had more coils and were taller. When installed they raised the rear of my car about an inch which kind of pissed me off. I wonder if they were the cc635 springs and the box was miss labeled. Or the WS6 rear spring were different than stock IROC rear springs. Mayby someone else who has swapped rear springs can chime in on that.
I honestly cant tell if the spring rates are different because my suspension prior to the rebuild was toast. I replaced EVERYTHING. I do like the way the car handles now .

 

I think your stock rear suspension might have been the cc635, and putting on the new 5665's raised it. Well, new springs will do that anyway... "More coils" I would think is the 5665's.

 

This from the F/M web site (though the link went dead):

The 5662 spring is rated at 748. Cross ref is 14047216
The 5665 spring is rated at 107. Cross ref is 10020763 or 10027654

Frustrating.

JamesC

 

Sonix my understanding was that the cc635 springs were "cargo coil" variable rate aftermarket springs that were supposed to raise ride height for people that had heavy sub enclosures and the like in the rear comparment. They were not a factory option. The 5665 springs were a linear rate true factory replacement. That's why I was suprised that the 5665 raised my ride height that muchand looked different from my stock springs.
James I agree that this is frustrating. I did alot of searches before purchasing these springs and there was alot of conflicting info on them. I finally gave up and just bought them anyways. Like I said the front 5662 springs appear to be a dead on WS6 replacement but the rear 5665 were different. I find it odd that there are so many front replacement options and only one linear rate rear spring option. Hopefully someone finds a difinetive answer for the spring rates and ride heights.

 

cc635's were put on factory, more commonly then the 5665's as far as I know.

It's not to help with heavy loads in the back (although, that is one benefit). It's just to give a non linear spring force. As you load it more, the springs get stiffer. It's very hard to hit the bumpstops with those.

There is a few moog spring charts floating around this forum and online, I guess one was posted here. Anything with the same free length, outside diameter, and same spring rate, will have the car at the same ride height. So basically, only stock springs will give a stock ride. Or if you use a shorter spring, with a higher rate, and do the math, you can get it to ride the same height, just be stiffer.

FWIW - I run the 5664's, and cc635's. I wanted the rear end raked, for that dragster look, and it worked a bit. Not much. The fronts are nice and stiff, and it rides like it's a true sports car. It's not all that uncomfortable riding around in it, the road hugging ability offsets the harshness of ride to me.

 

Frustration x 2: I went to Summit. After some searching, I found the following: Mog-5662, 85-90, IROC only. Couldn't find a spring rate; however, Mog-5610 was listed for a 90 IROC without 16-inch wheels. The spring rate for that application was 424 lbs/in.

JamesC

 

The Camaro Performance Handbook: Performance Modifications for 1982-1992 Camaros by David Shelby repeats the info found in a link above: "Most front spring rates range between 300 and 350 lbs-in. for base coupes, with IROC-Zs and Z28s with rates of 548 lbs-in.!"

So (he heaves a pitiful sigh), I've learned this much: Moog front replacements are either 748 or 706, depending on what chart you investigate (or 424 for some years at Summit), the rears 107 (two versions linear or variable). Spohn sells "IROC style" springs, his version being 648 and 107. And the above source says fronts are 548.

Since there appears to be no verifiable info on this matter, I may simply throw caution to the wind and go with the Moog and/or Spohn "IROC style" replacements and some Bilstien HDs. Better ideas?

I just located this info in an 1985 specifications booklet and found it to be generally interesting though there is no mention of IROCs:

Suspension, Front--spring rate (lb/in): L4 & V6, 331.0 lb/in; V8 & F41, 365.0 lb/in; Z28, 548 lb/in.

Suspension, Rear--spring rate (lb/in): 103 lb/in, exc Z28, 131.5 lb/in.

JamesC

 

Does that book tell is that rear spring linear or progressive?

Jari

 

It doesn't. Here's another link for further info:

https://www.thirdgen.org/forums/hist...=1#post3127774

JamesC

 

My 91 Specifications show the following spring rates in N/mm (lb/in):
RS - 64 N/mm (366) Front, 18/25 N/mm (103) Variable Coil Rear
Z28 - 96 N/mm (548) Front, 23.0 N/mm (131.5) Z28 & F41

From www.federal-mogul.com (Moog/TRW) I found the following:

Front
5602 - 347 lb
5608 - 424 lb
5660 - 548 lb
5662 - 748 lb

Rear
CC635 - 104 lb Variable Rate
5665 - 107 lb

Couldn't find any other listings for the rear.

Just called Moog Tech. 5660 is for Z28 front w/o air, 5662 is for Z28 w/air. CC635 is recommended rear for RS. No rear available for Z28. For what it's worth.

Just checked with my local Chevy dealer on the 1LE springs:
14029396 Front - Discontinued. May be able to order from Chevy VPI.
10018091 Rear - Replaced by 10305134. In stock.

Again, for what it's worth.

 

Put 5665 on rear of 1985 Iroc-Z along with complete rear suspension rebuild. Car sits at stock height as it was when I bought it new in 1985. Rides fine. May be too high for the guys that like lower cars. Badman

 

I decided to go with Hotchkis for my 86 Iroc and got completely burned. The springs were shorter and softer and although it looked nice, the car was hitting the bump stops every second. It sounded and rode horrible. It bounced more than a Buick. Plus, I could barely get my jack under the car!

Needless to say, I went back to stock and never looked back.

 

Badman when you replaced your rear springs with the 5665's did they look the same as the sock springs you took out? They had more coils than my stock WS6 springs. I was wondering if the stock IROC rears were different from TA's and Formulas.

 

They were the same in height and number of coils. If you need the number of coils I can let you know tomorrow as I will be working on the car. Don't remember offhand. Badman

 

Are the 1LE springs better or the same as the MOOG springs? I am confused about the difference between the rear springs. I am still trying to grasp the concept of the different type of springs. I have sportlines and the rear is way to soft, bottoms out all the time on the bump stops. I have Spohn everything and bilstein HD's in front and sports in the back.

 

FYI: Spohn's IROC style springs have a rate of 748 and 107 (5662 and 5665). A correction has been posted on his site.

JamesC

 

So he just sells Moog springs and never bother to get the spring rates right. Well done.

 

To answer the question, are ws6 rear springs the same as the IROC. The answer is yes, atleast from 85-90 after that I am not sure. Over the weekend I replaced my rear springs with moog 5665 and they look identical to the ws6 rear springs. I also put new tokico hp shocks on, forgot to mention I cut 1/2 coil off the springs and got about 3/4" lower than stock. I did the same to the front about 8 months ago with moog 5662 and tokico hp struts. Car looks and handles great, back is slightly higher but should settle soon. I have a friend who has the same struts and shocks but has the Eibach Proline springs, cars sit almost identical heights and I think mine handles better, not mushy in the back for about 1/3 the price.

 

Sweet, good info there, thanks Joe...

I'm looking to lower my WS-6 GTA a bit - about 1.25" - 1.5" in the front, & .75" to 1.25" in the rear. Does anyone know how I can do that while still retaining all of the handling that the WS-6 is known for???

My wife has asked what I want for my birthday, & what I really want is to lower my car a bit - but given the extreme frustration/confusion present with this subject, I'm holding off until I have some idea WTH to do...

Solid advice would be hugely appreciated... Thanks guys.

 

From what I'm understanding the best value/results is the moog replacements? Is that about right guys?

I'm wanting to do get 1" drop V8 Springs for my V6 so the I maintain stock height while gaining a stiffer suspension. This would be about right wouldn't it?

 

Yes, moog is best value and same results.
Moog only makes factory springs, not drop springs. Bust out the cut-off wheel if you want 1" of drop.

 

So what were to happen if I were to put the moog iroc replacement springs on my 90 rs. I want to replace my springs but want a stiffer ride and stock height.

 

most people find the car sitting much higher with the moog iroc replacement springs.

 

Yeah and don't put in new insulators either... I put in new ones and they were from a 4th gen apparently even though I bought them from GM classic parts and they called it a 3rd gen spring isolator.. That raised the back quite a bit higher than the front in comparison. All around though the car did raise quite a bit but it's decent and very acceptable to drive around. Stiffness is great and the springs do settle a bit over time giving it a good stance.. If only I didn't put it those isolators in the back.. sigh.

 

I'm buying a set in a few weeks, i might like the 1'' lift the moogs give the rear end for bottoming out purposes. I have 17" wheels how stiff are these springs?

 

I believe OE ride height is 27 1/2. My Moog IROC replacement springs (#5662) actually lowered the car a bit to approximately 26 1/2. The Moog 5665's jacked the rear up to nose bleed height. To lower it to OE ride height I was forced to use radiator hose in place of the insulator, then cut some of the coil.

BTW, I've often read about springs 'settling', but that wasn't the case with mine (they were in the car nearly a year, IIRC, before I started the above mod and they hadn't settled a fraction).

JamesC

 

I agree with the rear being a bit too high... Maybe an inch lower and it would be a perfect 1" rake instead of the 2" rake or wtv it is now.

 

27.5" at stock height is too low. It's gotta be higher.

Hellz_wings has an 88 IROC with the 5662/5665 combo. His heights are:

LF 28.5 RF 28
LR 29 RR 28.25

Now contrast that to my heavier 89 GTA with original suspension.

LF 26.8 RF 27.75
LR 27.5 RR 28

This is a difference of the following heights.

1.7......0.25
1.5......0.25

My passenger side now, after 20 years is still higher than 27.5"...... I've looked at the pictures of Hellz_wing's car on his website and I gotta say, I think his suspension height looks perfect. My passenger side still looks about the same as always. But my driver's side definitely looks like it's needing replacement. Essentially stock on the right and Eibach Sportline on the left.

I'm looking at doing new struts/shocks, springs (5662/5665) sometime in the next month or so. I'll report back on before/after heights and see if I can get some good pictures too.

 

Hey Reid,

Thanks for the compliment on the height! I wouldn't call it perfect, but my personal preference would be a tad bit lower.

A big thing that differs from ours is the weight, as you mentioned, i've shaved almost 250lbs of weight off the car, mostly from the front of the car. Also, my battery is on the passenger side while yours is on the driver side, so that might account for the driver's side being lower than the passenger.

Those numbers of yours, is that with you in the car or out of the car? Mine were when I was out of the car and it was on level ground.

I actually plan on moving the battery to the rear spare tire and jack area which will raise the front a bit and drop the rear slightly (hopefully!). I don't think it will be that much of a difference, but it will help. The rear springs aren't stiff enough in my opinion so I think cutting them will 1) make them shorter to give a more even height with a slight rake, and 2) will raise spring stiffness to give it a firmer ride in the back. The front stiffness is really good it's so much firmer than the old stock springs!

 

The thing I like about your height is not just the height itself, but that the driver side is slightly taller than the passenger side. So with you in the car, the heights should be pretty much level. And it gives you more time for the future when the springs eventually start to sink.

My height measurements are with nobody in the car. I suspect the reason the driver's side on mine is so much lower than the passenger side is that 99% of the time, it's just me driving the car. So that's an extra 230 lbs in the driver's seat that doesn't usually exist in the passenger seat.

Maybe my shocks on the driver's side are more worn out. Who knows. I'm definitely looking forward to the Koni Yellow + Moog 5662/5665 combination that should be happening soon.

I don't know if cutting the rears would make them that much firmer. The backs are only about 100-110 lbs or so not cut. So the percentage gain would be quite small compared to cutting the 700 lb springs up front.

 

Here's some info for Z28/IROC owners that might prove interesting and/or useful:

Height**

Vehicle height 50.3
Cowl point to ground 35.6
Rocker panel--front to ground 7.9"
Bottom of door closed--front to ground 14.3
Rocker panel--rear to ground 7.8

Ground Clearance**

Front bumper to ground 13.7
Rear bumper to ground 13.0
Rear axle differential to ground 7.2

**All Vehicle Height and Ground Clearances Are Made Using EPA Loaded Vehicle Weight, Loading Conditions.

(EPA loaded vehicle weight is the base vehicle weight plus all coolant and fluids necessary for operation plus 100% of the fuel capacity, plus the weight of all options and accessories which weigh three pounds or more and which are sold on at least 33% of the car line, plus two occupants)

The above is from GM's Camaro 1985 Specifications handbook.

JamesC

 

Ah jeez James, now we're all going to have to go and measure all those.

 

Good info!! I'll have to wait till march / april to measure that since car is away in storage.. It seems as if we'd have to measure with two people in the car to get the same reading?

 

Wait stock height from the ground to the chin spoiler on an iroc is 13.7"?


REALLY? If that is the case then my car must be at least 5" lower than stock, with 28" tall tires all around....wow.

 

That's the way the diagram shows the measurement; however, I'd guess the 13.7 is from the ground to above the spoiler (since it isn't a bumper). At any rate, the measurement would make more sense there.

JamesC

 

I know this is thread is over 9 years old but it sure helped me out with picking new coil springs for my IROC. Bought the Moog 5662/5665 coil springs yesterday from Rock auto for less than 110.00 shipped. Will be cutting 1/2 a coil off as suggested in this thread.Thanks to all that put this info up.

 

 

What was your ride height after installing the springs i installed sport lines last year and hate them I live in Texas and it is way to low for these roads

 

Here's the info direct from MOOG/Federal Mogul.

http://www.moogproblemsolver.com/moo...rings_Spec.pdf

 

SOCAL-Z, were you ever able to get those parts installed and take measurements and pics?

Im curious to see the results of the spring swap.

 

GM still makes a stock replacement also. They are more expensive than the Moogs though.

 

I have the rears on will be installing Founders Panhard bar relocation kit and LCA relocation brackets this weekend. Just started on the front this past Sunday should have it on the ground by next week.

 

Rear is at 28 1/2 with 1/2 a coil removed and gas a just KYB shocks.