Impala SS Stock Spring Replacements???? - Chevy Impala SS Forum
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post #1 of 26 (permalink) Old 02-20-2018, 10:01 PM Thread Starter
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Impala SS Stock Spring Replacements????

What's the recommended replacements for STOCK front and rear replacement springs. Have a buddy with 200K+ on a 96 SS that is sagging quite a bit. What to replace with???
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post #2 of 26 (permalink) Old 02-21-2018, 06:25 AM
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Can't answer, but occurred perhaps many out there would love your sacked out coils. Sell, don't discard.

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post #3 of 26 (permalink) Old 02-21-2018, 09:11 AM
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There's been no Exact replacement of recent. Some suppliers offer replacement SS springs but exact specs are unknown. There are a couple of close replacements from moog. Slight height differences, plus or minus and same for stiffness. Any preferences?
For rears:
5387 - a touch stiffer at 157lbs/in vs stock 154. negligible. and a touch higher, should sit about 0.3" (1/4 inch basically) higher.

5415 - 10% stiffer at 170lbs and 0.1" shorter

6381 - 30% stiffer at 199lbs and same height as 5387 with stock weight.
If you have more junk in the back, it would drop less than with a stock spring. I run these in the 91. You may want to pick different shocks depending on what kind of roads you have. They were too much for our rough new york roads with the soft bilsteins and would be loose when jacking up the rear. I found the station wagon(shorter) kyb to work great with them.

Fronts are a little tougher getting something close 'out of the box'. Are you adverse to cutting them?

584 - touch stiffer at 457lbs/in vs 440 stock and should sit 0.5" higher once settled. So if you cut the spring 1/4" shorter, you would be right at stock height and about 5% stiffer than stock

586 - little softer at 433lbs/in and around 1/8-3/16 inch shorter.

other choices require cutting for sure
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post #4 of 26 (permalink) Old 02-21-2018, 10:02 AM
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I'll have to do a little digging, as the name of the company escapes me at the moment, but I bought stock Impala specification springs from an aftermarket manufacturer last year.

I didn't like that both Eibach & Hotchkis rear springs dropped my car so much that my old exhaust system tail pipes (Clear Image) used to scrape when entering and exiting my dad's driveway.

I couldn't load the trunk with anything without it significantly dropping the rear of the car too much for my liking.

I also was not impressed/happy with the air bag route either, so that's what made me choose the stock spring height.

My pic in the SIG is with those springs installed.

....Okay, I was able to find the contact information for the company on my work PC. Here ya go:

Coil Spring Specialities: 785-437-2025

BTW, I also found a full-size photo I took right after install so you can see the ride height too.

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Last edited by juniorwatson; 02-21-2018 at 10:06 AM.
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post #5 of 26 (permalink) Old 02-22-2018, 05:02 PM
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I can't remember the brand but I replaced my rear shocks with air shocks. Easy mod and they work very well. Adjustable and yields a solid ride.
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post #6 of 26 (permalink) Old 02-22-2018, 05:38 PM
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Sorry to mislead you. You were asking about springs and I answered regarding shocks.
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post #7 of 26 (permalink) Old 03-31-2018, 12:43 AM
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Quote:
Originally Posted by Bob Lane View Post
What's the recommended replacements for STOCK front and rear replacement springs. Have a buddy with 200K+ on a 96 SS that is sagging quite a bit. What to replace with???

I would take the rear springs if you are throwing them away
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post #8 of 26 (permalink) Old 04-17-2018, 12:21 PM
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I had a thread a long time ago where I was decoding springs, but can't seem to find it. I'm fairly certain the stock SS rate was closer to 120 #/in. If you still have your SPID, post up your spring codes. Note if it's an Impala or Caprice too. RPO's for rear springs start with 8 and 9, like 8RS & 9RS, fronts will be 6 and 7. I can cross reference the RPO with the spring broadcast code.

I'm actually looking for a stock rate or SOFTER rear spring that also lowers the car about 1.5". I currently have the Moog 750 #/in front springs, and the car is still tail happy trailbraking into the corners, so trying to reduce rear roll moment, and roll stiffness.

Michael -1979 Caprice LS1 - e.t.... recomputing
1996 Caprice 9C1 LeMon's Car
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post #9 of 26 (permalink) Old 04-17-2018, 05:22 PM
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Quote:
I'm actually looking for a stock rate or SOFTER rear spring that also lowers the car about 1.5". I currently have the Moog 750 #/in front springs, and the car is still tail happy trailbraking into the corners, so trying to reduce rear roll moment, and roll stiffness.
What Moog 750#in lowers the car 1.5"?
I am fairly sure the Moog 80098 and 7268 springs are similar and provide near stock height.

From the forum's information I increased the rear springs to match.
Moog 7268 Front Ford 150 97-03 Dodge Van 79-80 750Lbs
Moog 5419 Rear Caprice 79-96 173Lbs

How will a softer and lower spring help you?

Quote:
I can cross reference the RPO with the spring broadcast code.
If you have this resource please post it for all.
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post #10 of 26 (permalink) Old 04-17-2018, 05:44 PM
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Quote:
Originally Posted by Z09B4U View Post
What Moog 750#in lowers the car 1.5"?
I am fairly sure the Moog 80098 and 7268 springs are similar and provide near stock height.

From the forum's information I increased the rear springs to match.
Moog 7268 Front Ford 150 97-03 Dodge Van 79-80 750Lbs
Moog 5419 Rear Caprice 79-96 173Lbs

How will a softer and lower spring help you?

If you have this resource please post it for all.
I was told the 80098 lowered the car about 3/4" from Impala height. I don't have fender trim, and am running a much shorter tire (255/40-17) so it's hard to eyeball where I'm at right now.

The spring info I have is in two different tables. I can match RPO to broadcast code, then look up the broadcast code to get rate and free height info. It's not all 1 database, and I can get to it because I work at GM.
The spring chart I have shows 5 different rates, but I don't think all these springs are just for B cars, they might be for other coil spring rear (Gbody??) Applications too. I see 19,21,24,27&37 N/mm for the rear. I'm fairly certain that the rear on an Impala or 9c1 are 21N/mm aka about 120#/inch, not 175. Oddly, 21N/mm is not on your chart.

Why is a lower rate what I want to try? When you go into a corner, the body will roll, since the front is heavier than the rear the body rolls more where the front wants to go. If you have a lot of roll stiffness in the rear, you will end up unloading the inside tire, lose grip and tend to oversteer. An extreme example of this is the 80's and 90's VW's, where they lift the inside rear. Nose heavy, high roll stiffness in rear, body rolls, rear suspension does not.


I can try a softer rate which MIGHT help that. Not sure. I can reduce roll stiffness by removing the rear bar too and let the rear become more compliant. I can also add more front bar to reduce roll up front.

I can lower the rear, which should shift the roll moment.

I don't think I need stiffer rear springs, especially since the car is lighter than stock, and I have no plans for passengers or cargo, it's strictly a race car now and has been for 10 years. I'm trying to make it a faster race car.


Or, I can just learn to drive the car better, and not dump off the gas mid corner, transfer load off the rear of the car and make it loose.

I need to figure out something, I damn near spun the car in the dry, and the car was REALLY easy in the wet and caught two of my codrivers by surprise.

Below is a pic of the car trail braking, see how light the inside rear is?

Sent from my Moto Z (2) using Tapatalk
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Michael -1979 Caprice LS1 - e.t.... recomputing
1996 Caprice 9C1 LeMon's Car
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