2002 Chevrolet Corvette Z06: The Mystery of the Leaf Spring
June 28, 2010
Whenever someone around here trips over a reference to the transverse leaf springs in the Corvette's suspension, they recoil in horror. You can see that it makes them think of some kind of bad pickup truck, not a sports car.
Of course, the Corvette's use of the leaf spring isn't what you think. For one, these are not springs located longitudinally on an axle, locating the axle and providing suspension action. Instead the springs are mounted transversely, one between each of the front wheels and the other between each of the rear wheels.
So fine, you say. Instead of a pickup truck, what we have here is some kind of cross-springer racing car from the 1940s. But it turns out that the Corvette guys were up to something when they first adapted this design to the platform of the Corvette C4, introduced as a 1984 model.
When we were all standing around the bare chassis of the Corvette C4 at Riverside International Raceway in 1982, just as horrified at the presence of a leaf spring as you are now, Corvette chief engineer Dave McLellen explained his choice. It had a lot to do with packaging, he said. It was about an effort to keep the first all-new Corvette in 20 years as low and narrow as possible. And with a sports car that carries a lot of V8 engine under the hood, a transverse leaf spring solved a lot of problems.
In the process of making the design work, McLellen said, the Corvette engineers learned a few things. First of all, a transverse leaf spring weighs less than two coil springs, a factor of even more importance when you consider that coil springs represent unsprung weight, which affects the compliance and precision of suspension action. And as McLellen later pointed out in his book about his time as the Corvette's chief engineer, Corvette From the Inside (2002), the change in spring material from steel to fiberglass reduced weight by more than 30 pounds.
There is also some cleverness in the impact of the transverse leaf spring on handling. The engineers discovered that when the leaf spring was located by twin mounts in the center of the car, it gave them some effect on body roll, a crucial attribute when it came to getting the most from the then-new, super-wide Goodyear tires. As a result, a smaller anti-roll bar can be used for fine tuning, which reduces overall weight and also fosters more ride compliance, plus the suspension geometry isn't compromised.
Of course, when you see that the Corvette C5R and C6R racing cars have been converted to coil-over suspension, it's easy to start thinking once again that coil springs are the answer. But while such a setup makes it possible to optimize corner weights and tune a chassis for racing, it doesn't deliver anything you'd want to drive on the street, since wheel travel is so restricted.
As you can tell from this cutaway drawing of the C5 that legendary artist David Kimble created for GM, there's a lot of stuff inside the Corvette. And as Kimble could tell you, it takes a lot of effort to get it all in there. A transverse leaf spring might seem crude, but instead it's an example of the unique style of integrated engineering that's so typical of the Corvette.
Michael Jordan, Executive Editor