Composite mono-leaf w/ watts VS 4-link (DSE or similar)

[31 SONIC]

Something says to just go with a 4-link but I was wondering if a composite mono-leaf with Watts link would be a viable choice.

I can do Hypercoil composite springs, Delrin bushings, Watts link and the same Koni shocks that DSE sells in their kit for virtually the same price.

I know it's hard to beat a 4 link and I'm probably just thinking too much. I am not a suspension engineer by any means, so maybe someone else can tell me hell no, or it's a real good idea.

Vehicle is a 71 Nova. It would have a 275 tire in front and a 315 tire in rear. Mostly street driven, but it would see our local road race course more than a few times a year.
What do you think about the idea?

[Silver69Camaro]

What is the intended purpose of the car?

Personally, I'm using composite mono's. Many road racers can't say enough about them. However, I'm not sure if Nova's have the same rear leaf geometry as Camaros. If they do, it's pretty tough to top a well thought out leaf setup.

But, any link style suspension will offer adjustability that would otherwise be difficult to obtain with leafs.

As far as the watts goes, there's several schools of thought on that one:
1. Hyperco recommends a lateral locator with their composite springs, while other manufacturers say it's not needed. Personal experience of most people seems to all say it isn't needed either.
2. Defining a roll center may or not be necessary...only you can determine that for your vehicle.

I'm going to try it without a panhard/watts first, and go from there. Good luck!

[mazspeed]

Do they make a composite leaf spring for the camaro?

[Silver69Camaro]

Originally Posted by mazspeed

Do they make a composite leaf spring for the camaro?

Yep, both Hyperco and Flex-a-Form makes them. Roughly $400-500 for a pair. I've got a set of 200lb Hyperco springs.

The kicker: they're about 10lbs each!

[PTAddict]

Originally Posted by Silver69Camaro

Yep, both Hyperco and Flex-a-Form makes them. Roughly $400-500 for a pair. I've got a set of 200lb Hyperco springs.

The kicker: they're about 10lbs each!

The low weight - mostly unsprung weight - and lack of static friction between leaves make these look very attractive on paper.

Do you know the stiffness (modulus of elasticity) of composite vs. steel? Given that the spring width will be the same, if the modulus of elasticity was much lower than steel you would get more lateral deflection and maybe want a lateral location device. If stiffness is close to the same, then I don't see why they'd need lateral location aids any more than steel leaves ...

[PTAddict]

Out of curiosity, I just weighed my newly delivered QuadraLink setup. Complete weight in the packaging, with everything except axle brackets, was 89 lb. Subtract maybe 10lbs for packaging, you're at about 80, with about 40 lb of that partially sprung. That seems to me about the total weight of a pair of steel multi-leafs, shackles, and shocks, but less unsprung weight. And obviously, more than a pair of composite leafs with shackles and shocks.

Coils and shocks: 13 lb.
Control arm and panhard mounts: 16 lb.
Control arms and panhard bar: 31 lb.
Shock/coilover crossmember: 29 lb.

[Silver69Camaro]

I've tried to get some E numbers with limited sucess.

What I have found out that these tend to have more torsional stiffness than a comparable leaf spring, so consider that when calculating anti-roll bar diameters. On the other hand, lateral control of the axle is less than steel...but there's more to it than that.

First, in my case, I'm going from a spring with a 6" arch to 4.5". Reducing the arch shortens the moment arm that acts against the spring...causing it to twist and therefore lateral axle movement. Second, first gen Camaros have pretty good leaf geometry (tapered in front) which again increases lateral stiffness. If the geometry weren't as it is, I'd probably have to add a panhard for sure.

Back to the modulus question. Steel is easy, we all know that one. But, for the composite, it's way more complicated and I couldn't just compare the two numbers. The E in one direction (bending) may not be the same in another (lateral), depeding on the layout of the matrix material. Sheesh, I wont even try to compare two different brands of composite springs if the binders and fibers are different. Ah, aren't composites fun?

In the end: I'll just have to run them to find out and add roll stiffness (or remove) to suit...then I can make a comparative analysis between steel and "other" leaf springs. If I need to had a lateral locator, no big deal. So far, others haven't needed to. Should be interesting.

[Silver69Camaro]

Originally Posted by PTAddict

Out of curiosity, I just weighed my newly delivered QuadraLink setup. Complete weight in the packaging, with everything except axle brackets, was 89 lb. Subtract maybe 10lbs for packaging, you're at about 80, with about 40 lb of that partially sprung. That seems to me about the total weight of a pair of steel multi-leafs, shackles, and shocks, but less unsprung weight. And obviously, more than a pair of composite leafs with shackles and shocks.

Coils and shocks: 13 lb.
Control arm and panhard mounts: 16 lb.
Control arms and panhard bar: 31 lb.
Shock/coilover crossmember: 29 lb.

This is interesting.

So that works to about 30lbs of unsprung weight, and add another:
38lbs (roughly) - Ford 9" axle housing
18lbs (roughly) - Axles
71lbs - Limited slip diff
45lbs - Aftermarket discs

Equals about 200lbs of unsprung weight, which isn't bad. Obviously I'm not including 100lbs for tires, wheels, hardware, roll bar, etc. But this should be good to compare.

For a composite leaf:
172lbs -Axle housing (same as before)
4lbs - Spring bads
3lbs - Shackles
10lbs - Springs (half of total spring weight, some controversy here)

Total of 189lbs. So, we save about 11lbs of unsprung weight. Not a whole lot, and personally, if cost weren't an issue, I'd trade this weight for the adjustablility of a link suspension (I think). We'll see when the car is pushed to the limits.

[mazspeed]

Originally Posted by Silver69Camaro

Yep, both Hyperco and Flex-a-Form makes them. Roughly $400-500 for a pair. I've got a set of 200lb Hyperco springs.

The kicker: they're about 10lbs each!

Is there a website for these? I would also like to know the lateral deflection as well, good point by PTAddict.

[Silver69Camaro]

Originally Posted by mazspeed

Is there a website for these? I would also like to know the lateral deflection as well, good point by PTAddict.

http://www.hypercoils.com/Products/H...f-Springs.aspx

You won't get a specific "lateral movement" number, but they usually say a locator usually isn't needed for the street, but may be needed for sticky tires on the track.