FHA spring question
Thread Starter
Melting Slicks
Joined: Nov 2018
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From: AA/Metro Detroit
FHA spring question
I was looking at my springs tonite, and I noticed that my front is marked FHA, which various tables around here indicate is a 93.1 spring rate. It is supposed to be an RPO FE1, is a 1992, I was not expecting to see that. I was examining this because I was interested in possibly taking it up to the Z51 specs springs, and this is what I was going to buy anyhow. I was told it was stock in this regard, and it definitely has the stock shocks, were these actually built with FHA up front? It is also marked with 1-5 under FHA, is this some sort of date code, or is there any other way to tell if this is a replacement?
The rear is the expected NYR 39.9, I just find it odd the front would be swapped and not the rear.
The rear is the expected NYR 39.9, I just find it odd the front would be swapped and not the rear.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
I was looking at my springs tonite, and I noticed that my front is marked FHA, which various tables around here indicate is a 93.1 spring rate. It is supposed to be an RPO FE1, is a 1992, I was not expecting to see that. I was examining this because I was interested in possibly taking it up to the Z51 specs springs, and this is what I was going to buy anyhow. I was told it was stock in this regard, and it definitely has the stock shocks, were these actually built with FHA up front? It is also marked with 1-5 under FHA, is this some sort of date code, or is there any other way to tell if this is a replacement?
The rear is the expected NYR 39.9, I just find it odd the front would be swapped and not the rear.
The rear is the expected NYR 39.9, I just find it odd the front would be swapped and not the rear.
Like you, I found it odd that a DPO would change the front and not the rear. Maybe just careless documentation by GM.
Le Mans Master
Joined: Sep 2013
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From: near the thumb in the mitten
Original front spring failed and the FHA was available. PO didn't like how car cornered. It's hard to say. FHA is rated the same as the Z07 although not the same code. The Z07 / Z51 rear spring NYU would complement the FHA
Team Owner
Joined: Sep 2003
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I don't believe the FHA is an unusual find in most any year C4. In the past I've had FHA removed from a '91 and also an FHA removed from a '93. These were known to be from a '91 and a '93. There's very different fabrication used on the ends of the spring. If you check closely there's I believe an 1 1/4 X 1 1/4 pedestal on the control arm end of your spring. Through '91 there was only a molded pad on the control arm end. If you search eBay for FHA spring you'll find snapshots and images of both fabrications. Way to much is 'assumed' using these suspension charts etc on the Internet!!
Date codes on the later with 1 1/4 X 1 1/4 pedestal I believe is on the top side of the spring.
This eBay offering has an image with the dated information on the top side.
https://www.ebay.com/itm/88-96-Corve...Cwqs:rk:2:pf:0
Notice that regardless the fabrication everyone sells fronts as '88 through '96. That just 'ain't so' - Fit yes but very different!!!
**** The actual production code is in a block of the 'BUILD SHEET' Give the NCM some of your $$$
Date codes on the later with 1 1/4 X 1 1/4 pedestal I believe is on the top side of the spring.
This eBay offering has an image with the dated information on the top side.
https://www.ebay.com/itm/88-96-Corve...Cwqs:rk:2:pf:0
Notice that regardless the fabrication everyone sells fronts as '88 through '96. That just 'ain't so' - Fit yes but very different!!!
**** The actual production code is in a block of the 'BUILD SHEET' Give the NCM some of your $$$
Last edited by WVZR-1; Dec 6, 2018 at 02:31 PM.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Hib Halverson made a chart listing the different spring codes FHA was the base front spring for a coupe 88-91 FSS base 92-95 FSK 92-95 Z07.
NYR base rear spring 86-93
Although unlikely early 92 assembled with in correct front spring.
The spring pad on the FSS is just a square attached to the center of the tip verses a large full tip pad.
NYR base rear spring 86-93
Although unlikely early 92 assembled with in correct front spring.
The spring pad on the FSS is just a square attached to the center of the tip verses a large full tip pad.
Thread Starter
Melting Slicks
Joined: Nov 2018
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From: AA/Metro Detroit
Cool, well I guess that saves me a couple hundred bucks and saves me some work on something I wanted to do anyhow! I plan on getting the NYU to match, and the beefier bars.
I've only had the thing a week, give me some time!
I've only had the thing a week, give me some time!
Thread Starter
Melting Slicks
Joined: Nov 2018
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From: AA/Metro Detroit
Hmm, guess some other things came through between me opening the page and actually hitting reply earlier. Does that mean that later FHAs aren't really that high of spring rate, that they are, or that no one has any clue? And perhaps more importantly, is there a way to positively ID one of the 90ish spring rate springs on eBay? I'd hate to replace what I have with the same thing, or worse, replace it with something softer. Or maybe I just replace the shocks now and with the plan of dealing with new-new known springs after I run it a while.
Team Owner
Joined: Sep 2003
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Hmm, guess some other things came through between me opening the page and actually hitting reply earlier. Does that mean that later FHAs aren't really that high of spring rate, that they are, or that no one has any clue? And perhaps more importantly, is there a way to positively ID one of the 90ish spring rate springs on eBay? I'd hate to replace what I have with the same thing, or worse, replace it with something softer. Or maybe I just replace the shocks now and with the plan of dealing with new-new known springs after I run it a while.
You said "I've only had the thing a week"
What makes you 'think' you need a thing? If you don't understand the effort required in spring replacement (on the front) and have a very good reason to actually 'NEED' - I believe you drive it and enjoy!!!
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Le Mans Master
Joined: Aug 2015
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From: St. Charles MO
As noted, you have the base spring that would have come in your car (FE3). In 1991 there was no Z51 according to the Halverson chart, but the Z07 for 1991 had the same spring rates as the previous year's Z51, and these are commonly known as the "Challenge" springs. The front spring for this is coded FHB, and it's 115.5N/mm. The rear spring is NYU with a rate of 57.2N/mm. So you could find these springs and do your upgrade, which would get you to the 1991 Z07 spec (or 1990 Z51 spec). Swap to the solid 30mm front swaybar and 26mm rear and your suspension is then full Z07.
Thread Starter
Melting Slicks
Joined: Nov 2018
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From: AA/Metro Detroit
You maybe answered your own question!!!
You said "I've only had the thing a week"
What makes you 'think' you need a thing? If you don't understand the effort required in spring replacement (on the front) and have a very good reason to actually 'NEED' - I believe you drive it and enjoy!!!
You said "I've only had the thing a week"
What makes you 'think' you need a thing? If you don't understand the effort required in spring replacement (on the front) and have a very good reason to actually 'NEED' - I believe you drive it and enjoy!!!
Basically, I don't want shocks to be something I have to repurchase if I get halfway through the year and decide to bump up spring stiffness. Plus, ripping it apart and putting it back how I want it is the only fun I can have with it til April, it is much easier to work when it is already up on stands and ripped apart, and in the Spring I'd rather be driving it
Last edited by jefnvk; Dec 6, 2018 at 09:32 PM.
Le Mans Master
Joined: Aug 2015
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From: St. Charles MO
That is precisely the path I'd normally take, to be honest I'd prefer if I really had a time to trial it with these. However, I bought it for AutoX, and the shocks absolutely need done (its sitting on the originals with 170k miles, and really needs brakes and every other wear item done) before the Spring. Being keen to shocks and springs working together, before I decide which direction to go with shocks, I was trying to figure out what was the best solution with springs.
Basically, I don't want shocks to be something I have to repurchase if I get halfway through the year and decide to bump up spring stiffness. Plus, ripping it apart and putting it back how I want it is the only fun I can have with it til April, it is much easier to work when it is already up on stands and ripped apart, and in the Spring I'd rather be driving it
Basically, I don't want shocks to be something I have to repurchase if I get halfway through the year and decide to bump up spring stiffness. Plus, ripping it apart and putting it back how I want it is the only fun I can have with it til April, it is much easier to work when it is already up on stands and ripped apart, and in the Spring I'd rather be driving it
Thread Starter
Melting Slicks
Joined: Nov 2018
Posts: 2,096
Likes: 1,024
From: AA/Metro Detroit
It will serve as a nice Friday to work and fall color run type cruiser as well, I don't want to take it quite to full race suspension. Shooting for ST class, still haven't quite decided between Koni adjustable shocks and shipping the OEMs off to Bilstein with the springs they'll be used with and telling them to valve them in a street performance/AutoX manner. I'll look into those Ridetechs too, haven't heard much about them.
Never realized the build sheets were more detailed than the RPO label, maybe I should pick one of those up sooner rather than later!
Never realized the build sheets were more detailed than the RPO label, maybe I should pick one of those up sooner rather than later!
Le Mans Master
Joined: Aug 2015
Posts: 6,091
Likes: 1,972
From: St. Charles MO
It will serve as a nice Friday to work and fall color run type cruiser as well, I don't want to take it quite to full race suspension. Shooting for ST class, still haven't quite decided between Koni adjustable shocks and shipping the OEMs off to Bilstein with the springs they'll be used with and telling them to valve them in a street performance/AutoX manner. I'll look into those Ridetechs too, haven't heard much about them.
