Corvette Leaf-spring Suspension’s Analysis

Aug 28
20:44

2013

Olivia Tong

Olivia Tong

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The Corvette was not the first car to combine leaf springs with independent suspension. As well as the Triumph Herald, Fiat did something similar in the 50s with steel springs. The recent Volvo 960 Wagon (not sedan) also used fibreglass leaf springs in the rear with independent suspension. The Corvette is, as far as I know, the only vehicle that uses this setup both front and rear.

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The Corvette was not the first car to combine leaf springs with independent suspension. As well as the Triumph Herald,  Corvette Leaf-spring Suspension’s Analysis    Articles Fiat did something similar in the 50s with steel springs. The recent Volvo 960 Wagon (not sedan) also used fibreglass leaf springs in the rear with independent suspension. The Corvette is, as far as I know, the only vehicle that uses this setup both front and rear.

 

The system is definitely independent, not like a live axle or a twist beam rear end. With dependent systems, when one wheel moves, the other is forced to move too. The design of the Corvette suspension is such that even though both sides are linked one side can move without affecting the other, hence its classification as independent. But how - what about that leaf spring? Surely if it's attached to both sides, that makes this a dependent suspension system?

On the older Corvettes (C2, C3, C4 rear end) the leaf spring was rigidly clamped to the subframe in the centre. That made it act like two separate leaf springs, one for each side. As two separate leaf springs it, like a torsion bar, was simply an alternative to coil springs.

When considering coil-spring type suspension, the 'third spring' is essentially forgotten - the two visible coils are considered to be the springing part of the suspension. Not so - there's the anti-roll bar too. Whilst not technically a spring, it does act as a transverse torsion bar linking both sides of the suspension together.

So the way GM started using the tranverse leaf spring is actually very clever; it lets one spring act as both a traditional spring and an anti-roll. Yes - if one wheel moves, spring forces (not geometric displacements like we see with a live axle) are applied to the other wheel - however, in a car with an anti-roll bar the same thing happens (see the section on anti roll bars). The problem was that it worked well as a spring, but not so well as an anti-roll bar, so in the end GM had to add anti-roll bars too.

 

Typically, aftermarket tuners will tear the leaf springs out and replace them with coil spring systems simply to make life easier. GM left many things on the Corvette with room for improvement. Leaf springs are not really a fundamental problem - typically the view is that Corvettes would be no better from the factory with coil springs. A traditional leaf spring live axle saves money because the cost of leaf springs is less than coils, trailing arms, pan hard rod etc. The Corvette has all the same suspension arms as a system with coil springs, so the only difference is the cost of the fibreglass leaf vs. the cost of the coil spring; leaf springs cost more than a coil so GM didn't do it to save money. It's not immediately clear then why they did it other than perhaps 'because they could'.

 

To round off this section then, here is an excellent link talking about how this suspension works - it does a far better job than I can: Fibreglass springs

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