Hey all-
Got an '89 IROC and have been contemplating messing with the suspension. Just deciding whether or not to mess with it has been hard enough, let alone deciding what to change/what parts to think about using. I haven't decided - but I'm still reasearching parts such as springs that are on the market.

My main ? is what are the rates of the original springs? If I knew that, at least I'd have something to compare to all the aftermarket springs out there. Are there any GM publications out or something stating what spring rates I've already got?

Sorry if this has already been answered - new here..... and there is a tone of great info here on springs already, just couldn't find a definite answer to this.....

Kevin

 

No ideas huh? I gather from a more recent post that they are liner rate springs - at least that can be said.
It would be nice to know - then we could easily compare to other replacment springs or stock springs on Vetts etc.

Buehler? Buehler?.................

 

https://www.thirdgen.org/techbb2/sho...oc+spring+rate

https://www.thirdgen.org/techbb2/sho...oc+spring+rate

https://www.thirdgen.org/techbb2/sho...oc+spring+rate

 

https://www.thirdgen.org/techbb2/sho...hreadid=207098

i just posted the specs for someone else

 

For an iroc front spring rate is 547in.lbs & Rr is 130in.lbs.Same for a z28.Springs are linear from everything ive read.GTAs use a softer front spring(500 in.lbs).Rs camaro use 350 in.lbs up front.Rears are all 130 in.lbs

 

Hey guys - very cool! Thank you, thank you, thank you!!!!

So between what laiky and and 84 1LE said - there seems to be a discrepancy - what gives? Are the Moog springs OE replacements with different numbers than from the factory - in actuality, a stiffer spring than original?

84 1LE - where did you get those numbers? I'm just curious, that's all - not questioning that they are correct, just interested.

All this interest is because I'm interested in maybe changing springs but I don't want to lower - want the original appearing height for authenticity sake. I might go down up to 1 inch, but that's all and it seems, unrealistic too. So, guess I'm stuck with stock height.

Oh, yeah - where do WS6 springs fit in - what are their specs if anyone knows? Actually, being new to GM cars in general, are WS6 springs only on 4th gens, or were they made for 3rd gens too, originally I mean?

Kevin

 

Aftermartket spring rates are all there own.I know in the back of some old TRW catalogs they use to list the spring rates for their springs.They were always different than factory rates.I would think moog is the same.If you want a factory spring rate your stuck with original replacement springs.As for the spring rates i listed.I got those from various G.M type manuals & magazine tech articles.GTAs came standard with WS6 suspensions.WS6 was optional on all other firebird models(t/a,formula,etc). 4th gens are different though.

 

That helps to clear up the WS6 question.

So, it's not so much that I want to maintain factory springs rates as much as it is factory ride hight. Now I got to figure out what springs will give me a similar ride hight and have a different spring rate.

We all know Vetts tend to handle pretty dang well - I wonder what the spring rates are on them? Well, that's broad - lets say mid-90's vettes for instance? I'm well aware that the entire suspension package is much different on a vette, but just comparing springs, how do they differ?

 

i run the moog 5665/5662 combo and the ride height is about factory. maybe a little higher than stock iroc but i would say about right for a z28, easy to trim to fit if you ask me.

 

Vettes actually have softer springs.Mostly because theyve got a IRS & much bigger tires/wheels & theyre lighter.Which lets G.M. use softer springs.Now if want a diferent spring rate(which i think you mean stiffer.Maybe what i did might be of interest.I wanted to lower my car,but only 1in.So i used a GTA spring(500in.lbs)in place of my stock z28(548in.lbs).In the same aticles that i read about the spring rates.It says if you cut a spring by 1/2 coil you raise the rate by 10%.So i cut the GTA spring by 1/3 coil.Which gave about a 7.5% stiffer spring.Multiply that by 500in.lbs.Gives you a 538 in.lbs spring.Slightly softer than stock,but with all the mods to my suspension(poly bushings/sphericle rods on panhard bar & Rr LCAs,16 vs 15in wheels,Hotchkis swaybars,SFC.My car droped about 7/8in. in the end(close enough)The ride is a little stiffer than a stock 84Z.Now if you were to cut a gta spring by 1/2 coil & add 10% to the spring rate you get 550in.lbs.It just depends how much you want to lower your car.Youll have to experiment though.Hope this helps

 

84 1LE
It does help - alot.

So, is cutting springs bad? Seems like I've read both ways - some people think it's ok and others think it's not a good idea?

I like your idea though - looks like you achieved the kind of drop I'm interested in getting. Tell me if this makes sense - if I wanted a stiffer spring rate and some lowering, like we said before, could I get both by cutting my current, factory IROC springs? Maybe a better question is - do I really want to cut the original springs???

Acutally, that brings up another question - do you know how cutting the springs changes spring rate to make it have a higher rate?

Definetly helpful - thanks for the input - the more the merrier ;-)
K

 

Cutting springs has its pros & cons.Some say its O.K.some say not.Personally i think its O.K. AS long as its not more than 1 COIL or a 1in.drop.The more of the coil you cut the less it seats the way its suppose to.Because the coil windings are closer together at the top & bottom of the spring.The more you cut off the farther away the end/tip of the coil is to the coil directly below it.This causes the coil to stand at an angle instead of straight up like it should.Also cutting the coil changes the geometry of the suspension.Becauses the wheel will tilt inward at the top.Which will cause the inside of the tire to wear out faster.This will also cause the inside tire in a turn to lift(slightly)on the outer part when cornering hard affecting your handling.AGAIN this is minimal if you dont lower your car more than 1in(at least by cutting the coils).Drop spindles dont cause this because they move the spindle up on the steering knuckle.This does not change suspension geometry,but the drop spindle is a 2in.drop(too much for my tatse).Which is why i went with cutting the coil.YES you can get both a stiffer/lower ride by cutting your iroc coils.It just depends on how stiff a ride you want.Originaly i cut my z28 springs by 1 coil.Eventually though it got to a point where i couldnt stand the ride(too stiff)because the Z28/IROC springs start with a 548in lbs rate + the 10% increase i got by cutting them.Gave a spring rate around 603in.lbs.So i decided to switch to GTA springs when i found out they are 500in.lbs & the same height as the Z28 springs.This allowed me to lower my car w/out a stiffer ride.Anytime you cut any coil it becomes stiffer because the coil is handling the same weight(your car) as before,BUT its now shorter.So there are less coils supporting the weight of your vehicle & now the spring cant compress as much.So you get a stiffer spring.Its sort of like trying to compress any spring by hand.The more you compress it the harder it gets to keep compressing it as it shortens.This happens to a coil spring if you cut it also,because you effectively shorten it.As far as cutting your springs it depends on how you want to keep your car(stock/original or modified).Nothing ive done to my car (including cutting the springs cant be reversed.If i ever wanted to return it to stock.Which as far as springs are concerned i would just by new or replacements.It just depends on your personal veiws i guess.Theres pros & cons to that issue as well......