Cars - Corvette leaf springs

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	Cars - Corvette leaf springs

This article is about leaf springs used on the GM Chevrolet Corvette
. While most other cars use coil springs, the Corvette uses leaf springs.

In suspension designs where leaf spring systems are tasked to hold the axle and function as a spring (modern truck suspension), multi-leaf springs suffer from friction between the leaves as the system flexes. The inherently flexible leaf spring is being asked to work as a spring and a suspension arm. Springs (leaf, coil, torsion etc) are good at being springs. They are not good at being rigid links. To its credit, the leaf spring does this much better than a coil spring. For example a coil spring may be viewed as a bobble head doll in the same tasked assigned to truck-style leaf spring designs.

The Corvette has double A-arm suspension like many other high end sports cars. The A-arms are used to fully control the movement of the wheels. The only difference between the Corvette and other cars with A-arms is the Corvette uses a leaf to pull the lower arm down rather than a coil spring to push it down. In both cases the spring is doing what it does best, being a only a spring.

Another problem with leaf springs is friction between the leaves of a leaf spring. The Corvette however uses a single piece leaf in its design so there is no internal friction, just like a coil spring.

So the Corvette's leaf springs design is similar to double A-arm geometry just with a different type of spring.

Other types of leaf springs

Model T style transverse leaf

This model shows the transverse leaf used on a Ford Model-T. The suspension has two lateral arms that keep the front axle perpendicular with the chassis. Lateral axle movement is controlled by the spring. This system suffers from poor control of the axle's movements among other flaws.

Conventional truck type, longitudinal leaf springs

This is the only type of leaf spring suspension still in use. It's cheep and durable but suffers from poor handling caused by friction between the leaves and from poor control of the axle's location.

Golf cart style transverse leaf spring

This design is similar to a double A-arm design where the leaf spring is one of the A-arms. The geometry is stable under vertical loads but lateral loads could defect the spring and cause camber changes.

Leaf with links

There are variations on this suspension:

Miller Indy Roadster and (on top of the front axle)
Jaguar MkII rear suspension

Like #3, these suspensions uses a combination of links and the leaf spring to support the axle. The Jaguar set up looks similar to a 4 bar solid axle rear suspension except the lower link is the end of an inverted leaf spring. The other end for the leaf is attached to the chassis under the passenger compartment. The middle of the upside down (frown rather than smile) spring presses against a rubber block. The end connects to the bottom of the axle. This system offers better handling and axle control than #2 but is still suffers from friction between the leaves of the springs and compared to multi-link live axles, poor control of the axle's location.

Leaf springs on the Corvette

GM started using leaf spring type suspension in the Corvette in 1984. Before that time there were coils in the front.

Advantages

Leaf spring suspension weighs much less than coil springs. One leaf replaces two coils. The two coil springs weigh 3 times as much as the one leaf.
Leaf springs help by lowering the center of gravity of the vehicle by being placed at the bottom of the Corvette.
Leaf springs act as an anti-roll bar. The article above explains how this works so I won't. The advantage is you can run lighter anti-roll bars because the springs are taking care of part of the job for you.
The leaf springs never wear out. The vendor of these springs has never had to replace one due to fatigue failure. Coil springs do wear out but you typically don't notice on smaller, lighter cars. You do see it more on old, heavy Caddies and such. The improved fatigue life was really evident compared to the C3's steel leaf spring. Thus this is an advantage over coils but not a big one.
They are easy to adjust. One or two hand tools are all that's required to adjust ride-height, and some people are able to adjust the springs with the car on ramps and without removing the wheels.
They allow the shock to be mounted as far out as possible. Coilovers allow it as well, but require the springs to be mounted at the top of the assembly, which is bad for the center-of-gravity. They also allow for a non-existent shock tower, which in turn allows for a lower fender/hoodline.

Drawbacks

They are expensive. We normally don't think of leaves as the expensive suspension, but in the case of the Corvette, coils would be cheaper. Coils are usually easier to install as well. In the C5/C6, the lower ball joint must be popped on one side for the spring to be pulled out. It's also impossible to run stiffer springs left-to-right, so a transversely leaf sprung car would be a poor choice for oval tracks.

[ Visit the complete Wikipedia entry for Corvette leaf springs ]

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