Kris,
That's not quite right. Taken from the
"Ask CRG Archives" (question #121):
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121. Is there any difference in ride or handling between the 4 or 5-leaf springs? Why did GM put the 4-leaf springs on Z28 instead of 5-leaf springs? Is there a difference in ride height?
Dave McBride, 18-Jun-1999
[This was asked on the Camaro Institute (CI) and answered by us there. Since CI has no archive and we felt this question was important to others, we repeat it here.]
1. There was not a five-leaf spring. There is an entire family of five-leaf spring designs (in 1968-69, only monoleafs were used in 1967). The family covers different spring rates, arch heights, and different maximum load design points. Springs were selected to create an equivalent vehicle position or stance in the loaded condition, depending on the gross weight of the vehicle. The one exception was the G31 spring series, which, as Heavy-Duty (HD) springs, were specifically designed with a higher arch and a higher unloaded ride, allowing them to deflect more on loading - resulting in a higher loading capacity. The G31 springs purposely cause a vehicle to sit up higher in the back until it is loaded with extra weight. However improper vehicle stance will also occur if the wrong spring is installed.
2. The (1968-69) Z28 was not limited to the four-leaf spring, nor was a (1968-69) non-Z28 prohibited from having a four-leaf spring. We have documented five-leaf Z28s and documented 4-leaf non-Z28s in our data, and the factory spring tables confirm that this was intentional. In particular, the F41 option on the 1968 L30/M20 resulted in the four-leaf spring being applied to a non-Z28. The 4-leaf spring was lighter but also with reduced resistance to wind-up and decreased damping. If the weight of options so warranted it, the Z28 was equipped with certain five-leaf springs.
A detailed CRG Research Report is in preparation but it is coming along slowly due to the enormous amount of time required to do it right, and due to competing needs from other projects and from the CRG web site.
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Ed