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I am pulling my differential soon. I want to be prepared to replace my spring pending your answers. I have a flaw in mine which has been stable for decades (see pictures taken today). The spring has been painted over once in case anyone wonders why the crack is the same color as the surrounding material.
The flaw notwithstanding, is there a "life span" for these springs? Does their performance degrade with time and cycles? It is, of course, 38 years old and hasn't sat around- it has 219.000 miles. That means I'm beginning to have difficulty finding something I have NOT replaced at least once. The spring and differential are on that short list.
The first picture is from underneath. The entire blemish is about 3" long, maybe a little more than 1/4" wide.
The second picture is from halfway back to the rear bumper. The blemish can be seen to the right of the center of the photo. just protruding from the surface of the spring about 1/4" or less.
Well, my VBP 360 monospring has been on my 78 L-82 gymkhana suspended C3 since 1986. Generally speaking a monospring should not wear out..AKA lose its compression/rebound characteristics, unlike a steel spring which WILL sag with time and will wear out..steel leafs will fatigue.
I have a few questions.
Who made that spring? How long has that very slight splinter/crack been present? The one fatal flaw has been that the composite springs can crack if they suffer road debris/damage. If that splinter has been there for a while, my guess is that the spring would be fine. HOWEVER, with the high mileage on your car and spring AND since you are going to R&R the differential any way, if it was me, I would replace that spring....if you only Occasional drive that car and the crack has been present for a while, I would leave it alone ......for now.
Last edited by jb78L-82; Mar 29, 2020 at 03:05 PM.
It is the original spring. The crack has been present for over 20 years and has been stable.
I drive it A LOT. Even used to commute with it to two daily jobs in the D.C. area.
Porposing is an issue to me. I wonder if renewing could dampen the rebound without making it ride like a truck. I am uncertain what the original spring weight was, but from my reading I think is is around 200.
How does your 360 feel?
Oh gosh that OEM spring was a marshmellow.....200 Lbs....
My 360 spring with Bilstein sport shocks in the rear only, rides perfect for me...firm but not harsh...I have Bilstein HD's in front with the 550 OEM springs. My car ride is NOT hard at all, just firm.
If you want a modern car ride (not a sports car but like any car today) I would suggest the 300/330 lbs composite with Bilstein HD shocks which will significantly tighten up the ride but will still ride smooth.
If you want a firm but not hard ride, 360 with Bilstein sports.....
Last edited by jb78L-82; Mar 29, 2020 at 03:31 PM.
Does yours ever porpoise or does it stop rebounding in one cycle?
I've achieved a much better ride and eliminated many rattles with new, adjustable rear camber links. My originals had bushings that were so worn the rubber looked like it was turning back into oil and there were even pieces of fossils in there.. When I hit minor bumps like sewer caps the sound is just a "thunk, thunk" instead of the sound of shaking a bucket of bolts. I've come a long way but there's always more to do with a driver.
Does yours ever porpoise or does it stop rebounding in one cycle?
I've achieved a much better ride and eliminated many rattles with new, adjustable rear camber links. My originals had bushings that were so worn the rubber looked like it was turning back into oil and there were even pieces of fossils in there.. When I hit minor bumps like sewer caps the sound is just a "thunk, thunk" instead of the sound of shaking a bucket of bolts. I've come a long way but there's always more to do with a driver.
Never porpoising...your 200 lb spring will cause that with weak shocks
The porpoising is definately the shocks. They are too weak for the spring. I have heard that the composite springs need a slightly stiffer shock than the steel ones to stop the porpoising, since the steel ones have more friction. So stock shocks meant for the steel spring may not work well.
The Bilstein shocks are very well recommended.
PS: If you have a factory spring, I would love to see a full rear end shot with the whole spring, while it has the car weight on it. Could you measure the spring bolts and see if they are 6.5" or larger?
Either would be appreciated.
Congratulations on driven it often! It looks great in Maroon.
Last edited by leigh1322; Mar 29, 2020 at 10:00 PM.
This view is from an alignment rack so the weight is all on the tires. (Ever seen such a clean driver with 219.000 miles on it?) If this isn't what you meant I will take more photos today in the garage. I will reply with bolt dimensions later today. I will look up the Bilstein shocks.
I would concur with the recommendation of Bilstein Shocks. I have them on all my Corvettes, (the '85 even came from the factory with them) and have always been pleased with the results. I even put them on my F-250, diesel Superduty and a '98 Tacoma.
We bought the Tacoma SR5 pickup new in '98 for our son to drive to school & college. When new, the factory shocks would make my wife sea-sick when we drove it... literally. I took it in to the dealer and they agreed the shocks were bad. They replaced them with the exact same shock - which proved to be no better. They would not upgrade to a gas shock under warranty, so I installed a set of Monroe-Matics that remained on there until 90k miles when I replaced them on a whim, with Bilsteins. The Tacoma now has 210k miles on it (running strong) and the shocks are as good as the Monroes were when new and much better than the factory Toyota shocks it came with new.
Products do change over time in quality, but Bilstein shocks seem to have remained a quality product for many years (35 years for me) and also at a reasonable price in my opinion.
I have Bilsteins on my 78 L-82 355, 94 Mustang GT Convertible, Doug Rippie Specially valved Bilstein Sports on my 10 C6Z06 and my 2008 Chrysler 300 with Bilsteins HD's. I have never had a Bilstein wear out or leak...never. There is not a better quality shock/Strut on the market for the money. NO contest!
Well THANKS, you've made it easier in one way but now I have another question:
The combo you are recommending sounds like it will deliver a pickup truck ride. Can you explain how a (stiffer?) spring and stiffer shocks won't be jarring? I really only wanted to address the porpoising. Not even sure why I should upgrade the spring.
I wouldn't bother if it's been that way for decades. You already like the ride so put decent shocks back on it and keep driving.
Agree ^^^^ just change the shocks.
Bilsteins unique characteristics are excellent handling with incredible decent ride quality.
A Composite spring's unique characteristic is that you can go MUCH higher with spring rate with minimal ride degradation compared to a steel spring. I would consider going to a 420lbs composite if I ever changed my spring since the ride is still a bit soft for my liking....My 10Z06, Lexus IS350 F Sport, Chrysler 300 with Bilsteins and even my Mustang GT with Bilsteins, ALL ride harder than my 78....with the 360 composite.
Last edited by jb78L-82; Mar 30, 2020 at 03:08 PM.
This view is from an alignment rack so the weight is all on the tires. (Ever seen such a clean driver with 219.000 miles on it?) If this isn't what you meant I will take more photos today in the garage. I will reply with bolt dimensions later today. I will look up the Bilstein shocks.
That's exactly what I was looking for! Thanks. I can almost guarantee you have 6.5" spring bolts based on the large amount of space to the wheel rim. I calculate your current as installed arch at a low 1.5".
Ans yes that is the cleanest high mileage non-restored car I have seen in quite a while. You obviously take terrific care of it. Congrats.
If you wanted to replace that due to caution, (the old crack) I would recommend the Van Steel EZ-ride it is an exact duplicate of your spring, made by the original manufacurer (Liteflex) on the original molds.
Thanks for your advice! I wish I could know how other cars felt with the various setups you recommend. Even though I am president of a Corvette Club, there are only 5 C3's in the club, a 69 and a 70 BB (both blue ribbon NCRS winners in the last two years), a beat up 78 that hasn't run in a couple years, another 82 and mine. Nearly everyone else has C7's.
Are you suggesting that the heavier composite springs will actually feel smoother over bumps and rattle the driver even less? Currently mine makes a very nice "thunk, thunk" sound over small bumps instead of a bucket of bolts sound. I think I have a little bit of body roll, nothing I couldn't take care of by lowering it or a rear sway bar. Again, I'm a cruiser, not a racer.
I have been moved closer to keeping my spring, installing the HD Bilsteins and continue driving.
The composite spring is certainly smoother than the steel. My 80 has a fairly stiff composite spring (385 lb/in, thanks to factory shortening by VB&P). With Bilstein Sports, it is still smoother than the stock 9-leaf steel and tired shocks in my 79. It goes ba-DUMP ba-DUMP ba-DUMP over bumps (bridge seams, for example), since the front is about as stiff as you can make it with a stock suspension. I'll go with 420 lb/in in the rear next time, and the 385 will probably get moved to the 79.
For your car, I'd absolute try the Bilstein HDs at all four corners first. That is a very clean car. Enjoy it!
Last edited by Bikespace; Mar 31, 2020 at 02:42 AM.
This view ,,(Ever seen such a clean driver with 219.000 miles on it?)
And,, I am so pleased that you have mounted the RWL tires with the RWL to the inside,, my personal favorite look,,
[[ just to be clear, I painted my white letters black, mounted inside,]] SOOO CLEAN!
When to Replace a Composite Rear Spring
SOOO CLEAN!