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Topic: rear leaf spring

in Forum: C3 Handling Components


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rear leaf spring (1/17)
 11/17/23 4:21pm
Dblancha79Gold Member
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Weatogue, CT - USA

Vette(s):
1979 C3 L82 383 cu in


Joined: 6/29/2015
Posts: 80

The rear end of my C3 is sitting 1-1/2 inches lower than the front. It would suggest that my rear leaf spring has sagged and needs replacing.  The one that is on the car is solid and not actually leafs.  Ekers and Zip corvette are selling these fiberglass rear springs in different weight ranges around $500. Any recommendations on what I should buy? 



|UPDATED|11/17/2023 1:21:58 PM (AZT)|/UPDATED|


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"Made to be run hard"
Simsbury, Ct.

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Re: rear leaf spring (2/17)
 11/17/23 5:18pm
Vette78RLLifetime Member
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Lawrenceville, GA - USA

Vette(s):
1978 Silver Anniversary. Restored in 2012. All new 'complete' suspension f & r, engine, trans, exhaust, interior. Car is driven - garage kept but not a trailer queen.


Joined: 10/21/2013
Posts: 28

Replaced my metal spring with a fiberglass rear spring in 2013.  My old one had the same issue as you're seeing with the sagging.  Since we were upgrading the entire suspension system to HD and poly, it was planned to replace it anyway.  We were building it specifically for mountain driving so installing everything performance-rated was important. 

They do come in different load ratings as you say, most often anywhere from 315 lbs to 355 lbs.  The one from Ecklers is 400 lbs.  Depending on how you drive it (just cruising, twisty mountain roads, straight interstate, etc. etc.), will determine what you buy.  A higher load rating will give you a stiffer feel, possibly even too stiff if you like a smoother ride.  The ride could be harsher on rougher roads.  Normal rule-of-thumb is for all around performance, the 340 lb is the choice.  355 to 400 are considered heavy duty and 315 is more or less standard.  Haven't been to the New England area of CT. and points north since living there 50+ years ago but I suspect that there are some nice "twisty's" up there to enjoy.  The 315 lb will allow more lean, probably too much, while the 355 - 400 could make it skittish on tight turns. 

Whichever you go with, it WILL be a marked improvement from the stock metal one.  To that point, Mid-America Motorsports has the 315 - 355 kits complete for $425 and Corvette Central has the same kits for $391. 

Re: rear leaf spring (3/17)
 11/17/23 7:01pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 874

Under normal conditions, the rear leaf spring should be basically flat with maybe a slightly up arch.  Don't remember when they switched to the fiberglass rear spring though.



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1973 L-82 4 spd

Re: rear leaf spring (4/17)
 11/17/23 8:15pm
Dblancha79Gold Member
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Weatogue, CT - USA

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1979 C3 L82 383 cu in


Joined: 6/29/2015
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Thanks, great info.



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"Made to be run hard"
Simsbury, Ct.

Re: rear leaf spring (5/17)
 11/17/23 8:19pm
Dblancha79Gold Member
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Weatogue, CT - USA

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1979 C3 L82 383 cu in


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Mine is basically flat under the cars weight. That is why I thought it was bad. Not sure what else would cause the back to be lower. Shocks are only a year old.



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"Made to be run hard"
Simsbury, Ct.

Re: rear leaf spring (6/17)
 11/17/23 9:08pm
F4GaryGold Member
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


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Maybe you can raise the rear with the spring bolts.  Shorter?



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Re: rear leaf spring (7/17)
 11/17/23 11:00pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 874

Gary has a point. Maybe someone replaced the stock spring bolts with longer ones. I know I did that to lower mine to even it up with the front end. The front end dropped a little when I put on the American Racing Vector wheels because they had another half inch of negative offset which caused the front end to drop somewhat.

 

Not positive but I believe the stock rear spring bolts were 6" long.



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Re: rear leaf spring (8/17)
 11/18/23 6:53pm
NorskyLifetime Member
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Burke, VT - USA

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SOLD - "The Beast" - '90 ZR-1 (#682)
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F4Gary said:

Maybe you can raise the rear with the spring bolts.  Shorter?

If memory serves I believe longer bolts are needed to lower the rear ride height.  Shorter bolts, or cranking them tighter, will raise the ride height.  It seems counter-intuitive but it works. 




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Re: rear leaf spring (9/17)
 11/18/23 9:51pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 874

Norsky said:
F4Gary said:

Maybe you can raise the rear with the spring bolts.  Shorter?

If memory serves I believe longer bolts are needed to lower the rear ride height.  Shorter bolts, or cranking them tighter, will raise the ride height.  It seems counter-intuitive but it works. 


You are correct but the OP wants to raise his ride height in the rear to match the front.




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Re: rear leaf spring (10/17)
 11/19/23 1:32pm
F4GaryGold Member
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


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Which ever way.  My point was that maybe his spring bolts are the problem. 🤷‍♂️



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Re: rear leaf spring (11/17)
 11/19/23 3:58pm
Dblancha79Gold Member
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Weatogue, CT - USA

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1979 C3 L82 383 cu in


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Thanks Guys, I measured my spring end bolts and they are 8 inch's long with the nut screwed up to max thread run out.  I ordered a threading die to cut some additional threads to get me closer to the 6-1/4 original equipment bolts. Will cut of the excess.  Thanks again for the help.



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"Made to be run hard"
Simsbury, Ct.

Re: rear leaf spring (12/17)
 11/19/23 10:22pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 874

You might check the head of the bolt to see if it's a Grade 8 bolt or not. I believe the 6" OEM bolts were Grade 8 for their strength. I mentioned this only because it might be hard to cut threads on it if it is a Grade 8.  



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1973 L-82 4 spd

Re: rear leaf spring (13/17)
 11/20/23 10:13am
manchestersharkLifetime Member
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Equinunk, PA - USA

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Just my honest opinion,  it may be easier to just buy a grade 8 bolt in the hardware store. They are not that hard to find. Chances are the one in the car may be the same quality, not O.E.M. 



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Re: rear leaf spring (14/17)
 11/21/23 10:06am
Dblancha79Gold Member
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Weatogue, CT - USA

Vette(s):
1979 C3 L82 383 cu in


Joined: 6/29/2015
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With a little work I was able to extend the threads on the 9/16 diameter grade 8 spring bolts.  Car is all set, was able to get the correct ride height back. Thanks everyone for your help.



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"Made to be run hard"
Simsbury, Ct.

Re: rear leaf spring (15/17)
 11/21/23 11:39am
NorskyLifetime Member
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Burke, VT - USA

Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
Still have - "BLKBRRD" - '78 Pontiac Trans Am


Joined: 1/23/2002
Posts: 7212

👍  👏



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Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

Re: rear leaf spring (16/17)
 11/22/23 2:51am
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 874

Just curious, was your 8" a Grade 8 bolt?

Edit: Oops, didn't read your last post.  😟



|UPDATED|11/21/2023 11:51:57 PM (AZT)|/UPDATED|


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Re: rear leaf spring (17/17)
 12/4/23 2:21pm
MackLS5
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1970 Bridgehampton Blue ext, Lt.Blue interior 454 M21 Cumberland, VA


Joined: 10/29/2021
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In 2021 I rebuilt my 70 LS5 coupe using a TRW mono leaf 340 lb. rear spring from Muskegon brake co. They were very helpful with the purchase.  The responsiveness in the rear has improved a lot. It’s a daily driver with typical curve roads medium speeds in my area of Va.  I noticed the best ride  improvement on the Blue Ridge pkwy last fall.  It did raise my rear height about 1.5 inches, which has put it just above the front height. You can lower the ride height by using longer bolts.  Good luck 



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