Help With Suspension Codes Please!
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
Help With Suspension Codes Please!
On the inside of the center counsel of my '90 I have both the Z51 code and FX3. It is a 6 speed car with the FX3 controller. On the suspension charts such as this one:
http://www.idavette.net/hib/c4/sustunch.pdf
I notice FX3 and Z51 have different springs and sway bars. I measured my stock bars thinking I had the Z51 option bars and they measure 26mm front and 22mm rear.
The springs seem pretty stiff so I am hoping I have the Z51 springs, but is there any way to tell without taking the spring out? Where is the code on the spring? Since I have both codes how did GM know which setup to use?
I am very dissapointed I dont have what I thought was on the car.
http://www.idavette.net/hib/c4/sustunch.pdf
I notice FX3 and Z51 have different springs and sway bars. I measured my stock bars thinking I had the Z51 option bars and they measure 26mm front and 22mm rear.
The springs seem pretty stiff so I am hoping I have the Z51 springs, but is there any way to tell without taking the spring out? Where is the code on the spring? Since I have both codes how did GM know which setup to use? I am very dissapointed I dont have what I thought was on the car.
Drifting
Joined: Oct 2008
Posts: 1,936
Likes: 92
From: Rochester Hills Michigan
On the inside of the center counsel of my '90 I have both the Z51 code and FX3. It is a 6 speed car with the FX3 controller. On the suspension charts such as this one:
http://www.idavette.net/hib/c4/sustunch.pdf
I notice FX3 and Z51 have different springs and sway bars. I measured my stock bars thinking I had the Z51 option bars and they measure 26mm front and 22mm rear. The springs seem pretty stiff so I am hoping I have the Z51 springs, but is there any way to tell without taking the spring out? Where is the code on the spring? Since I have both codes how did GM know which setup to use?
I am very dissapointed I dont have what I thought was on the car.
http://www.idavette.net/hib/c4/sustunch.pdf
I notice FX3 and Z51 have different springs and sway bars. I measured my stock bars thinking I had the Z51 option bars and they measure 26mm front and 22mm rear.
The springs seem pretty stiff so I am hoping I have the Z51 springs, but is there any way to tell without taking the spring out? Where is the code on the spring? Since I have both codes how did GM know which setup to use? I am very dissapointed I dont have what I thought was on the car.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
As for sway bars I mis-typed the first post. Its is 26mm front and 24mm rear.
Where on the bottom of the spring is the code? Can I see it if I jack the car up and look or does the spring have to come out.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Would FE1 or FE4 be on the code list under the lid as well? I did not notice anything with FE as I just remember seeing Z51 and FX3. I will check and get back to you guys.
As for sway bars I mis-typed the first post. Its is 26mm front and 24mm rear.
Where on the bottom of the spring is the code? Can I see it if I jack the car up and look or does the spring have to come out.
As for sway bars I mis-typed the first post. Its is 26mm front and 24mm rear.
Where on the bottom of the spring is the code? Can I see it if I jack the car up and look or does the spring have to come out.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
Thanks guys! Ill have to jack the car up and look. I hope I at least have the right springs. The bars are being swapped out for VBP 32mm and 26mm solid, but I would hate to have to buy new springs. 
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
Going from memory, but IIRC the Z51 / FX3 cars didn't get the heavy duty (Z51) springs or the larger sway bars (as you've already discovered). What they got was everything else, which outside of the 13" brakes wasn't much.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
89 and 90 owners got ripped off if they ordered FX3 with Z51 option
See
http://www.corvetteactioncenter.com/...fx3/index.html
"In '89, FX3 came only in combination with the Z51, but when you ordered those two, in a strange twist, the car was downgraded to softer, base springs, stabilizer bars and front lower control arm bushings. In 1990, FX3 no longer required Z51 but, if you ordered both, again, you got base springs, bars and bushings. Unfortunately, this downgrade was not widely known. Many unsuspecting '89/'90 customers, wanting the stiffer springs and bars, ordered Z51 along with FX3 but never knew their cars had base parts."
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
89 and 90 owners got ripped off if they ordered FX3 with Z51 option
See
http://www.corvetteactioncenter.com/...fx3/index.html
"In '89, FX3 came only in combination with the Z51, but when you ordered those two, in a strange twist, the car was downgraded to softer, base springs, stabilizer bars and front lower control arm bushings. In 1990, FX3 no longer required Z51 but, if you ordered both, again, you got base springs, bars and bushings. Unfortunately, this downgrade was not widely known. Many unsuspecting '89/'90 customers, wanting the stiffer springs and bars, ordered Z51 along with FX3 but never knew their cars had base parts."
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
I have got a 94 FX3 with the soft springs as well(I presume.) I put on the 32/26 sway bars, poly bushings and a couple other odds and ends keeping the soft springs. The car handles great. Spend your money on (4) 18 x 10.5 Z06 Speedlines with some sticky 295/30-18 tires all around instead of the springs, you won't be disappointed.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
I have got a 94 FX3 with the soft springs as well(I presume.) I put on the 32/26 sway bars, poly bushings and a couple other odds and ends keeping the soft springs. The car handles great. Spend your money on (4) 18 x 10.5 Z06 Speedlines with some sticky 295/30-18 tires all around instead of the springs, you won't be disappointed.
If anyone has or knows of a decently priced Z51 spring let me know. Or does anyone know how the VBP SPORT spring compares to the Z51?
Drifting
Joined: Oct 2008
Posts: 1,936
Likes: 92
From: Rochester Hills Michigan
[QUOTE=Kubs;1572274332]By they way, my code is FE7. What is that?
QUOTE]
FE7 is heavy duty front and rear suspension on my '92. (I just got this from the build sheet for the car. I was working from memory when I posted FE4; oops, sorry). FE1 is standard suspension.
You should have the stiff springs and bars. Hopefully, you have the FSB code on the front spring?
QUOTE]
FE7 is heavy duty front and rear suspension on my '92. (I just got this from the build sheet for the car. I was working from memory when I posted FE4; oops, sorry). FE1 is standard suspension.
You should have the stiff springs and bars. Hopefully, you have the FSB code on the front spring?
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
By they way, my code is FE7. What is that?
QUOTE]
FE7 is heavy duty front and rear suspension on my '92. (I just got this from the build sheet for the car. I was working from memory when I posted FE4; oops, sorry). FE1 is standard suspension.
You should have the stiff springs and bars. Hopefully, you have the FSB code on the front spring?
QUOTE]
FE7 is heavy duty front and rear suspension on my '92. (I just got this from the build sheet for the car. I was working from memory when I posted FE4; oops, sorry). FE1 is standard suspension.
You should have the stiff springs and bars. Hopefully, you have the FSB code on the front spring?
Another thing I found was in this thread while I was trying to see what prices Z51 springs were going for:
http://forums.corvetteforum.com/c4-p...-hardware.html
Post #4 says this
C4 Spring Code Chart
compiled by Hib Halverson
©2007 Shark Communications
Preface Notes:
1) GM had two RPO subsystems during the C4 era. There were engineering RPOs and marketing RPOs. What consumers knew as Z51 or Z07 was actually a combination of the FE3 (96) or FE7 (84-95) HD suspensions with other performance-related options. Some GM parts data refers to FE3 or FE7. When those RPOs are listed, it refers to cars optioned with either Z51 (84-91, 96) or Z07 (92-95).
2) In MY89-91, Selective Ride Control (SRC), which many refer to by its RPO, FX3, could be ordered in combination with Z51, however, a little-recognized production change which always occured in those MYs when those two RPOs were ordered together was a downgrade to base level (FE1) springs, front lower control arms and stabilizer bars. In those MYs the only conditions under which FE7 was present were; 1) if the car was ordered with Z51 and without FX3 or 2) it was an 90 or 91 Corvette Challenge car.
3) For MY92-95, FX3 and FE7 was added. A new RPO, Z07, was released for this combination. For MY92-95, FX3 was, also, available as a stand-alone option.
I know the best way is to crawl under the car and look, but being at school this week it will have to wait till the weekend, plus I like knowing the logic behind this. Does the quote in red mean since I have the Z51, FX3 AND FE7 codes that my car could be a challenge car and have the stiff springs anyways?
May this info could help other with their springs as well.I didnt know GM had so many ways to mismatch parts!!
Last edited by Kubs; Nov 30, 2009 at 10:04 AM.
Drifting
Joined: Oct 2008
Posts: 1,936
Likes: 92
From: Rochester Hills Michigan
Before I bought my '92, I spent a lot of time trying to figure out all the suspension configurations for the '84-'96 models.
I have no idea what is going on with your car unless it's a Challenge car. That would be great. Let us know what you find on the front spring.
One more thought: I've heard you can get the build sheet for your car from the NCM. That should clear up the confusion.
I have no idea what is going on with your car unless it's a Challenge car. That would be great. Let us know what you find on the front spring.
One more thought: I've heard you can get the build sheet for your car from the NCM. That should clear up the confusion.
Last edited by mashinter; Nov 30, 2009 at 11:22 AM. Reason: NCM
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
"In those MYs the only conditions under which FE7 was present were; 1) if the car was ordered with Z51 and without FX3 or 2) it was an 90 or 91 Corvette Challenge car."
Interesting.
My 90 has FX3, Z51 & FE7. It is not a challenge car.
Stiffer springs for better corner handlling is old school thinking. Just adding stiffer springs will help to a degree over a stock factory suspension however to make the best it can be you need to address all of the components.
Giver equal amounts of camber & caster change in both bump & droop:
A vehicle with softer springs, giant sway bars & good shocks will allow better tire compliance & corner faster than a stiffly sprung vehicle.
Interesting.
My 90 has FX3, Z51 & FE7. It is not a challenge car.
Stiffer springs for better corner handlling is old school thinking. Just adding stiffer springs will help to a degree over a stock factory suspension however to make the best it can be you need to address all of the components.
Giver equal amounts of camber & caster change in both bump & droop:
A vehicle with softer springs, giant sway bars & good shocks will allow better tire compliance & corner faster than a stiffly sprung vehicle.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
"In those MYs the only conditions under which FE7 was present were; 1) if the car was ordered with Z51 and without FX3 or 2) it was an 90 or 91 Corvette Challenge car."
Interesting.
My 90 has FX3, Z51 & FE7. It is not a challenge car.
Stiffer springs for better corner handlling is old school thinking. Just adding stiffer springs will help to a degree over a stock factory suspension however to make the best it can be you need to address all of the components.
Giver equal amounts of camber & caster change in both bump & droop:
A vehicle with softer springs, giant sway bars & good shocks will allow better tire compliance & corner faster than a stiffly sprung vehicle.
Interesting.
My 90 has FX3, Z51 & FE7. It is not a challenge car.
Stiffer springs for better corner handlling is old school thinking. Just adding stiffer springs will help to a degree over a stock factory suspension however to make the best it can be you need to address all of the components.
Giver equal amounts of camber & caster change in both bump & droop:
A vehicle with softer springs, giant sway bars & good shocks will allow better tire compliance & corner faster than a stiffly sprung vehicle.
I agree on not going too stiff which is why I want the Z51 springs. They are somewhere in the middle. the base springs are considerable soft, especially in the newer models, and the aftermarket springs eliminate the suspension entirely (exaggeration). VBP after market springs have a rate of 1066 lb front and 488 lb rear. Having a Z51 front spring (660 lb) and a base '84 rear (410 lb) would be a good balance to me. Not too stiff, but stiff enough for a good handleing car.
Like I said before I already focused on bushings/heim joints and big sway bars, now I am fine tuning to the spring rates I want, and then Randy at DRM is going to make a custom valved set of bilsteins to work with my setup.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
What spring rates do you have?
I agree on not going too stiff which is why I want the Z51 springs. They are somewhere in the middle. the base springs are considerable soft, especially in the newer models, and the aftermarket springs eliminate the suspension entirely (exaggeration). VBP after market springs have a rate of 1066 lb front and 488 lb rear. Having a Z51 front spring (660 lb) and a base '84 rear (410 lb) would be a good balance to me. Not too stiff, but stiff enough for a good handleing car.
Like I said before I already focused on bushings/heim joints and big sway bars, now I am fine tuning to the spring rates I want, and then Randy at DRM is going to make a custom valved set of bilsteins to work with my setup.
I agree on not going too stiff which is why I want the Z51 springs. They are somewhere in the middle. the base springs are considerable soft, especially in the newer models, and the aftermarket springs eliminate the suspension entirely (exaggeration). VBP after market springs have a rate of 1066 lb front and 488 lb rear. Having a Z51 front spring (660 lb) and a base '84 rear (410 lb) would be a good balance to me. Not too stiff, but stiff enough for a good handleing car.
Like I said before I already focused on bushings/heim joints and big sway bars, now I am fine tuning to the spring rates I want, and then Randy at DRM is going to make a custom valved set of bilsteins to work with my setup.
Here's a pic of the base 1996 front spring and the Hyperco spring..
Max G’s
Joined: Nov 2008
Posts: 2,751
Likes: 78
From: Monroe OH
NCM Sinkhole Donor
Install your 32mm front and 26mm rear and I think you'll be happy with that. I installed these and have an FE1 and body roll is nearly not and have plenty of stiffness in the suspension. I have even contemplated going back to a 30mm on the front. The rear 26mm is perfect. My set up is used for autox.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 9,682
Likes: 3,434
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
If I have to buy new springs I guess I will wait. Like mentioned we'll see how it handles with just the bar upgrade. Springs are not really in the budget now.
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA