Rear leaf spring

[Michael M.]

Does anyone know the difference between a single rate spring and a progressive rate spring ? I can only tell the difference by seeing two side by side. The 1963 spring I have all the leaf's are curved. The 1964-67 spring I have is what I call a 6/3 spring. This spring has 6 curved leaf's and 3 straight leaf's. I think the single rate spring would be the 1963 spring where all the leaf's are curved and touching each other. Thus, the 6/3 spring I think is a progressive rate spring. So besides the visual difference what else is different between these two springs ?

[Joe L.]

Re: Rear leaf spring

Does anyone know the difference between a single rate spring and a progressive rate spring ? I can only tell the difference by seeing two side by side. The 1963 spring I have all the leaf's are curved. The 1964-67 spring I have is what I call a 6/3 spring. This spring has 6 curved leaf's and 3 straight leaf's. I think the single rate spring would be the 1963 spring where all the leaf's are curved and touching each other. Thus, the 6/3 spring I think is a progressive rate spring. So besides the visual difference what else is different between these two springs ?

Michael------

1963 Corvettes used linear rate springs, front and rear. Thus, the front springs had equally spaced coils and the rear leaf springs had all curved leaves. This was true for both standard suspension and F-40 suspension although the springs differed for each suspension type.

Beginning in 1964 this changed. Standard suspension cars received progressive rate springs, front and rear. In this configuration, the coil springs have closer spaced coils at one end and the leaf springs have 3 flat and 6 curved leaves. This basic configuration continued for standard suspension Corvettes through at least 1974, if not through the end of C3 production.

F-40 and F-41 HD suspension cars used linear rate springs throughout the availability of those suspension options.

So, what's the difference between linear rate and progressive rate springs? Well, the basic difference is that progressive rate springs provide a better ride, especially over irregular pavement surfaces. Since all Corvette suspensions have always been rather stiff, I suppose that for 1964 GM engineers decided that they had to do at least a little to off-set this. Or, they decided that they were going to increase the spring rate so they went with progressive rate to partially off-set the ride harshness.

Linear rate springs provide more predictable and stable handling and that's why they were used for F-40 and F-41 suspension. These suspension systems were never designed or intended for on-road use. By the way, I don't recommend F-40 or F-41 for street driven, non-competition Corvettes, either. I would NEVER have such suspension on a street driven car I owned regardless of the "cachet" it might otherwise provide.