Monospring vs 9 leaf spring advantage ?

[Scott S.]

Re: Monospring vs 9 leaf spring advantage ?

You'll go nuts trying to find rear shocks with enough rebound damping to control the "bouncy-bouncy" syndrome the aftermarket monospring has; they have no interleaf friction to aid in damping their excursions, and you'll need a custom shock calibration. Good luck.

Do you have any insight about why GM didn't make the leaf-spring out of fiberblass, with multiple leaves, similar in design to the OE spring but with fiberglass instead of steel? Wouldn't that preserve the interleaf friction damping characteristic, while offering a (potentially) better ride?

[Bill M.]

Re: Monospring vs 9 leaf spring advantage ?

Do you have any insight about why GM didn't make the leaf-spring out of fiberblass, with multiple leaves, similar in design to the OE spring but with fiberglass instead of steel? Wouldn't that preserve the interleaf friction damping characteristic, while offering a (potentially) better ride?

You do not want friction damping. It is an objective of suspension design to eliminate friction damping. We measure friction and rate the car with the least friction as the best design. The '84 and later cars have fiberglass springs and no problem with shock control.

[Tom L.]

Re: Monospring vs 9 leaf spring advantage ?

From experience on glass monoleafs on stock cars I can tell you for sure that chips on the spring caused from debris on the track led to broken springs. After breaking a few we always wrapped them in tape to help prevent breakage, maybee GM had this concern about warranty issues.

[Michael W.]

Re: Monospring vs 9 leaf spring advantage ?

Is my understanding correct that the "smart strut" bracket (and similar products from other vendors) is basically a copy of the '68 or '69 strut bracket, which is about an inch or so lower than the stock midyear strut bracket, offering better suspension geometry?

Or does "smart struts" refer more to something about the design of the strut itself?

A strut is a strut is a strut. The 'smart' part the vendors push is the revised bracket which minimally reduces the amount of camber change of the rear wheels. Unnecessary for street driven cars IMHO.

[Duke W.]

Re: Monospring vs 9 leaf spring advantage ?

Eaton Detroit Spring offers a re-arching service, but how do you determine if it needs to be re-arched? If you just refinish it and add new liners, then won't something called "spring memory" cause it to sag back to its current (i.e., before refinishing and new liners) state?

In the archives I have read about both (re-arching vs. refinishing and installing new liners) and I'm trying to figure out which procedure is appropriate for a particular spring.

"Spring memory" is somewhat of a myth. As long as the spring has not been serverely overloaded and doesn't have significant corrosion, it should retain its original characteristics. So called "spring sag" on C2s is usually due to compressed spring link bushings and replacing them will restore ride height and considerably reduce ride harshness.

Just go ahead and disassemble, inspect, and refinish the spring. Install it with new link cushions. In the unlikely event that ride height does not meet spec (assuming the spring has not lost significant material due to corrosion), let us know. There is an easy solution.

Duke

[Scott S.]

Re: Monospring vs 9 leaf spring advantage ?

You do not want friction damping. It is an objective of suspension design to eliminate friction damping. We measure friction and rate the car with the least friction as the best design. The '84 and later cars have fiberglass springs and no problem with shock control.

Thanks for the reply, Bill.

So if I understand correctly, the interleaf friction damping characteristic is desirable in a multi-leaf metal spring, but would not be desirable in a multi-leaf fiberglass spring. I still don't understand why, but given that GM made figured out the "single leaf" fiberglass spring/shock combo and made it work on '84 and later Corvettes, why can't that system essentially be copied and resized proportionately for application to C2s and C3s with similar effectiveness?

That would seem like the obvious solution, so I'm trying to understand what it is that has caused aftermarket fiberglass rear spring manufacturers to 'reinvent the wheel' on this subject when GM had already produced a working spring/shock combo model. It's just something I've wondered about for a while now.

[Scott S.]

Re: Monospring vs 9 leaf spring advantage ?

"Spring memory" is somewhat of a myth. As long as the spring has not been serverely overloaded and doesn't have significant corrosion, it should retain its original characteristics. So called "spring sag" on C2s is usually due to compressed spring link bushings and replacing them will restore ride height and considerably reduce ride harshness.

Just go ahead and disassemble, inspect, and refinish the spring. Install it with new link cushions. In the unlikely event that ride height does not meet spec (assuming the spring has not lost significant material due to corrosion), let us know. There is an easy solution.

Duke

Thanks Duke. This car sat unused for a long time, I'll take a close look at the transverse leaf-spring to see if it's salvageable.

[Bill M.]

Re: Monospring vs 9 leaf spring advantage ?

So if I understand correctly, the interleaf friction damping characteristic is desirable in a multi-leaf metal spring, but would not be desirable in a multi-leaf fiberglass spring. I still don't understand why, but given that GM made figured out the "single leaf" fiberglass spring/shock combo and made it work on '84 and later Corvettes, why can't that system essentially be copied and resized proportionately for application to C2s and C3s with similar effectiveness?

That would seem like the obvious solution, so I'm trying to understand what it is that has caused aftermarket fiberglass rear spring manufacturers to 'reinvent the wheel' on this subject when GM had already produced a working spring/shock combo model. It's just something I've wondered about for a while now.

Interleaf friction is a necessary evil with a multi-leaf steel spring. That's why there are liners; to reduce friction. If you eliminate the inter-leaf friction, you probably need to increase the shock absorber damping; I don't know how much it has to increase.

Dave McLellan in Corvette from the Inside says the plastic spring is much lighter, cheaper, and has better fatigue life than a steel spring. He doesn't claim a ride improvement. That spring was introduced in 1981. I don't know what happened to the rear shocks in 1981, but Chevy wouldn't release a design that didn't work, so it can be done.

I don't know anything about the aftermarket fiberglass springs. I would expect that they would work just fine if they had the same spring rate as the factory spring and had shocks tuned to that fiberglass spring.

Bill

[Scott S.]

Re: Monospring vs 9 leaf spring advantage ?

Dave McLellan in Corvette from the Inside says the plastic spring is much lighter, cheaper, and has better fatigue life than a steel spring. He doesn't claim a ride improvement. That spring was introduced in 1981. I don't know what happened to the rear shocks in 1981, but Chevy wouldn't release a design that didn't work, so it can be done.

I don't know anything about the aftermarket fiberglass springs. I would expect that they would work just fine if they had the same spring rate as the factory spring and had shocks tuned to that fiberglass spring.

Bill

I read about midyear Corvette owners over on the CF who use one of the aftermarket fiberglass mono-springs, and a fair number of them seem to have problems getting rid of the "bouncy" problem that John mentioned in post #12 above, even though the shocks that come with those suspension kits are specially valved for the fiberglass rear spring application.

If GM made it work, I'm wondering whether the aftermarket fiberglass springs didn't copy the GM model correctly, or whether there is some other variable in the midyear suspension design which causes the mono-leaf spring to exhibit this undesirable "bouncy" characteristic that apparently is not a problem on Corvettes that were actually designed for them.

[Jack H.]

Re: Monospring vs 9 leaf spring advantage ?

The fiberglass 'monospring' made its debut on Corvette in 1981 (AT cars) and became standard across the line in '82. So, it wasn't just C4 and later cars that were factory equipped with this technology.

Why did multi-leaf steel springs persist for so long? I'll guess it was a matter of technological maturity (getting fiberglass with the right strength, elasticity, and durability characteristics) to make the monospring feasible as an alternative...

[Bill M.]

Re: Monospring vs 9 leaf spring advantage ?

I read about midyear Corvette owners over on the CF who use one of the aftermarket fiberglass mono-springs, and a fair number of them seem to have problems getting rid of the "bouncy" problem that John mentioned in post #12 above, even though the shocks that come with those suspension kits are specially valved for the fiberglass rear spring application.

If GM made it work, I'm wondering whether the aftermarket fiberglass springs didn't copy the GM model correctly, or whether there is some other variable in the midyear suspension design which causes the mono-leaf spring to exhibit this undesirable "bouncy" characteristic that apparently is not a problem on Corvettes that were actually designed for them.

I've seen them too. Ken Smith had a 330 lb/in fiberglass rear spring and 50 series tires. That is not bouncy, that is a brutally stiff ride. I think the word bounce is being mis-interpreted as bouncy. I'm reading bounce as "ouch". It's not the material, it's the spring rate.

I've had that experience with a 310 lb/in F40 spring and 60 series tires on my '65. It feels like your seat belt is gonna cut you in two on a large bump.

[Scott S.]

Re: Monospring vs 9 leaf spring advantage ?

The fiberglass 'monospring' made its debut on Corvette in 1981 (AT cars) and became standard across the line in '82. So, it wasn't just C4 and later cars that were factory equipped with this technology.

Why did multi-leaf steel springs persist for so long? I'll guess it was a matter of technological maturity (getting fiberglass with the right strength, elasticity, and durability characteristics) to make the monospring feasible as an alternative...

With the C3 frame being so similar to the C2 frame, would a 1982 Corvette fiberglass rear-spring and shock combo "bolt on" to a midyear Corvette without modification? If so, this might be worth exploring, for those who are interested in trying the fiberglass mono-spring on a midyear. I realize that's not what this Forum is about, I'm just trying to learn.

Thanks!

[Jamie F.]

Re: Monospring vs 9 leaf spring advantage ?

When I bought my '69 it had an aftermarket composite monospring on it. I purchased some shocks from Eckler's that were supposiddly designed for this spring in this application.
I then found an original 9 leaf and restored it and installed it.
IMHO the car rides and handles just as nice if not better with the original spring.
I had a back to back comparison and really cannot see any advantage to the "newer" spring over the original.

[John H.]

Re: Monospring vs 9 leaf spring advantage ?

If GM made it work, I'm wondering whether the aftermarket fiberglass springs didn't copy the GM model correctly, or whether there is some other variable in the midyear suspension design which causes the mono-leaf spring to exhibit this undesirable "bouncy" characteristic that apparently is not a problem on Corvettes that were actually designed for them.

I've yakked with many of those guys who have aftermarket monosprings ( from TRW, VBP, and Muskegon, in both load rates), and they're talking about "bounce", not harshness. The key issue appears to be that nobody makes rear shocks for that application with anywhere near adequate rebound damping, although VBP claims that theirs are calibrated specifically for the monospring application.

A C3 owner local to me went with the lower-rate VBP monospring, then went through four different sets of shocks (allegedly with more rebound damping) trying to cure the "bouncy-bouncy" syndrome, with little or no improvement. He gave up and went back to the steel 9-leaf with standard shocks, and he's a happy camper again.