So many years ago I 'upgraded' to a fibreglass monoleaf (late 1990's) .. I ordered the 360lb spring and received the 300lb spring... the annoying wide ended kind...

The spring is so soft the car would bottom out the suspension quite badly. I modified my driving, and avoided bad roads and whatnot but the damage was done... flattened exhaust, some scraped metal and a nice big hole in my spare tire carrier...

Fast forward many years to now, and I'm redoing the whole car. (body on resto) ..

I still have my factory 7 leaf, and the composite monoleaf.

I am seriously considering adding some of the steel leafs and plastic spacers to the monoleaf to increase the overall spring rate ...

has anyone considered doing this? any thoughts / concerns / insights?

 

Just buy a new composite spring. A failure of the composite spring due to your proposed modification would be catastrophic.

 

how so?

 

how are you going to prevent the steel ends of the spring from gouging the composite? How do you propose to stack the springs? Steel on top, steel on bottom? Seems like buying the correct spring is a lot safer. Did you use a quality gas shock when you installed the composite?

 

I don't think it is physically possible to have them both mounted at the same time.......???

 

I agree, not sure the concept is completely thought out. Composite springs come with spacers to make up for the thinner spring and still permit mounting bolts to go the correct distance into the differential cover.

 

I fully agree buying a new spring would of course solve the problem.

I have acquired a set of Koni adjustable shocks for all four corners, and when I begin the bolting on parts phase, they will certainly go on, in place of the old gabriels I had before.

Yes, this is just an idea I've been tossing about in my head, and having no posts from anyone anywhere that I can find on the subject got me more interested. And is why I'm asking the considerable knowledge base of this forum...

As for keeping the steel from gouging the composite, I have a few ideas. First using the plastic spring spacers, and secondly heating and curling the ends of the steel leafs upwards as well as using leaf spring straps at the ends such as what is used in many leaf spring setups.
In theory, that would eliminate any spring safety issues.

For the stacking I believe the only way it would work, (with the wide bottom spring I have), is to have the monoleaf on the bottom, steel leafs on top.

I realize the overall width of the stack should be the same and that width is critical to avoid damaging the case cover.
So removal of one or both of the monoleaf spacers, and/or fabricating spacers may be required.

I find the idea intriguing - combining mono and steel springs - wondering what that would feel like - how it would perform.

I fully admit although I have considerable mechanical and decent fabrication skills, I am out of my wheelhouse, so spitballing this idea seems like some good weekend fun!

 

The straps are supposed to be removed after installation to permit free movement. They are there for shipping purposes to prevent the leaves from fanning out. Heating will change the characteristics of the metal.

 

Anything is possible. It's only limited by one's interest, expertise, time, and money.

I enjoy engineering challenges. I've had, and currently have, a mixture of C3, C4, and C6 parts in my car's rear suspension. The money I saved adapting and fabricating stuff is payment for my time involved in those projects. If you enjoy fabricating stuff as well, give it a try. And please post pictures for those of us who enjoy custom projects.

 

I guess if I were going to do it, I would make some relatively thin (maybe 14 gauge) steel wear plates to go over the composite spring for the steel spring ends to ride on. I’d bend flanges down on each side so they stay centered over the composite spring, and then extend them out to the end of the composite spring so I can capture the bolt to keep the plates in place positively.
I think the center section damage concern revolves around the bolts bottoming out, so some careful math to figure out what length bolts you need to replace them with should take care of that problem.

 

Buy a low-arch composite spring direct from VanSteel this time, and if you get another Hyperco-style spring, return it.

Only it doesn't look like VanSteel even makes the "wrong" kind of spring anymore, so you should be fine.

 

The advantage of the composite monoleaf spring is that it's lighter and rides better, without sacrificing handling. It seems to me that stacking some steel leafs on the composite spring would both make the spring heavier and hurt the ride quality, thus counteracting all of the positive advantages of having a composite spring in the first place.

Additionally, composite springs are notorious for splintering and cracking from both age and exposure to heat from the exhaust pipes. Adding a couple steel leafs to the composite spring will change the spring rate by an indeterminate amount, possibly adding stress to what is already a 20+ year old composite spring of unknown condition, that by your own description was weak and insufficient for it's intended job when new.

I'm sorry, but what you're considering sounds like the worse of both worlds, creating a heavier spring that rides harsher, and yet at the same time may be more prone to failure.

Beside the fact that the bands aren't intended to remain in place on stock steel springs, I think it would be pretty difficult to band a composite spring to a steel leaf enough to keep the leaves from moving. I may be wrong about this, but I think the steel leaves are narrower then the composite spring, so no matter how tight you bound it, wouldn't there still be room for the steel leaves to move? Plus, binding the leaves too tight will effect the rate and characteristics of the spring.

I too don't like the idea of heating the leaves. Heating coil springs has been a somewhat common (and misguided) cheap and simple way of lowering cars since at least the early 60's, but it also weakens the spring, which is why it lowers the car. Heating just the ends of a leaf might not have as adverse effect on the integrity of a leaf as heating a whole coil does on a coil, but is it really worth finding out?

I've had a Corvette rear main leaf fail, and I admit the likely hood of any serious damage is quite slim. Basically all that happens is that the spring slams into the pavement and the trailing arm comes to rest on the trailing arm bumper on the side of the car the spring broke. The biggest result, other then having to replace the spring, is that unless you're a mile or two from home, you'll end up needing a ride on a rollback.

What you're considering probably isn't dangerous, and probably wouldn't cause serious damage if it didn't work, but is it really worth trying for something that by all appearances won't improve the effectiveness of the composite spring anyway?

 

The two springs don't have to be in physical contact, so no fiction wear or ride degradation. Just space the two springs a half inch (ballpark) apart at the center mount and out at the hanger bolts.

Is this dual spring concept ideal? No, but it's not as expensive as buying a new spring.

Done intelligently, I don't see a major problem.