1995 Caprice FE3 Factory Spring Rates? - Chevy Impala SS Forum
 
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post #1 of 7 (permalink) Old 10-12-2016, 02:56 PM Thread Starter
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1995 Caprice FE3 Factory Spring Rates?

Hello, Does anyone happen to know the factory front and rear spring rates for a 1995 Caprice LT1 B4U w/ the FE3 package and tow pack? Spring tag on rears is THH. I have heard that these are the stiffest factory spring put on 94-96 B-Bodies including Impala SS and 9C1's. Is this true? Car does ride like a truck...Which is OK...Has Monroe Severe Service shocks also that I put on...Thank you, Uvaldi..
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post #2 of 7 (permalink) Old 10-12-2016, 03:47 PM
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All the same except the soft FE1 sedan and station wagon.
77 n/m for fronts (440 lbs/in) and 27 n/m for rear (154 lbs/in)
Differences are free length to account for ride height or equipment installed.

FE1 get a 53 (303) front and an 18 (103) for the rear.

Wagons get 77 front and 37 in back (211).
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post #3 of 7 (permalink) Old 10-13-2016, 05:04 PM
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Thank you kindly. Question: is there a linear formula for calculating rate increase per fraction of coil cut off for drop? Case in point: Years ago I cut 1 coil off my old FWB FE1 fronts and it did not give desired drop. I cut off another 1/2 coil and it seemed to fall to the street, and kept bottoming out on dips. I ended up with plain 'ol SS coils all around.

On my new FWB I want to retain a little more of the floaty ride, just drop a little. For further reference, the difference between a 20-year old FE1 and 20-year old SS coil is exactly 2" in front. What's my new spring rate cutting exactly 3/4 coil off an FE1 front?
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\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #4 of 7 (permalink) Old 10-13-2016, 08:52 PM
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Sure. Not sure what happened with your case where 1 coil did not much yet 1 1/2 made a big difference. Maybe not fully seated first try?

For a simple spring, where it only touches at the very tips of the spring, it would be:

original coils/new coils x original rate

It's a little more complicated with our springs as they don't contact the frame nor control arm at the tips. The top has that roughly 1/2 - 3/4 of a flat coil that you wouldn't count and bottom is about the same how it sits in the arm pocket. So you need to count the effective coils where the spring stops making metal contact. So if you count the total, you need to then subtract that roughly 1 to 1 1/2 coils first. Then again after the cut. Before you divide orig by new.

Also useful. Our springs sit just about smack in the middle of the control arm. So if you install a spring with the same rate but shorter, the difference in free lengths when doubled, gives you the change at the wheel well.

Cutting a spring gives you actually less then double as you correctly realized the rate also increases when cutting.
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post #5 of 7 (permalink) Old 10-13-2016, 09:11 PM
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Actually, the FW FE1 springs are stiffer than b body FE1 springs in case you didn't know. Got a pic of your stock spring? Then can count how many coils you're starting with before you make the 3/4 coil cut. Need that to get the new rate. But as an example (coils are a guess):

Let's say it has 10 total to start. And we use worst case for most increase, that 1 1/2 coils don't count. So it'd be

8 1/2 / 7 3/4 x rate = 1.1 x rate. (10% increase)

Have at work, but think the D body FE1's are like 350 lbs/in. So you'd end up with 385 lbs/in if it were the value.

And if you measure how high 3/4 of a coil is, you'd know rough how much it drops it if you double it. A little less cause of the rate increase.

For a more accurate drop estimate, would need to know the actual FWB weight to account for how much effect that rate increase has.
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post #6 of 7 (permalink) Old 10-14-2016, 10:41 AM
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Quote:
Originally Posted by 91ss View Post
Sure. Not sure what happened with your case where 1 coil did not much yet 1 1/2 made a big difference. Maybe not fully seated first try?

.....
Quite helpful thanks. I am semi-recalling I did 1/2 a coil off first (trying to be conservative), and upon seeing nearly zero affect I did NOT want to keep re-installing those dam coils over and over so I wacked off a whole coil next and it was clearly too much for my liking. But I'm sure it would have been the perfect drop for some guys. Thanks for stepping through the math - confirms my thinking and you added a couple good points too.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #7 of 7 (permalink) Old 10-15-2016, 10:09 AM
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No problem. Ah, that makes more sense doing the 1/2 coil first then 1. I interpreted the other way around.
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