I just received the latest copy of Vette magazine and it was nice to see a multi-page feature on the C4 generation of Corvette, including (of course!) the legendary ZR-1. There’s scant coverage of the C4 these days and it sometimes feels as if I own “The Corvette That Time Forgot.”
The article discusses the history of the C4 including the reintroduction of the convertible in 1986, certainly a momentous event. However Vette mistakenly says that Dave McLelland designed the C4 vette with a convertible in mind and due to this, minimal changes were needed to encompass the roofless model. This doesn’t line-up with Dave’s own account in his book “Corvette From the Inside.” The real story is even more amazing.
Dave writes that there was no anticipation of ever doing a convertible version of the car. The official GM fluff was that convertibles were gone and weren’t coming back due to new stricter safety regulations. But that was just smoke and mirrors to cover the fact that those models weren’t selling (hard to believe now) and in reality was yet another cost-cutting exercise.
Originally the C4 was designed to have a T-roof, like the C3s. This design has a somewhat mixed reputation: though it looks quite neat, the design is prone to leaking. In Corvette From The Inside, Dave mentions that very late in the design cycle a top GM executive (not named but I’m guessing this must have been Roger B. Smith, then CEO) saw the new Porsche 911 and its distinctive “targa” top. The Porsche featured a completely removable glass panel so that even drivers of the “fixed roof” versions could enjoy open air driving. The GM Exec. was so in love with this that he insisted the new C4 should have the same feature.
The engineers protested, naturally. The chassis hadn’t been designed to encompass the feature and the bar running between the rear “hoop” and the windshield frame was a key structural component necessary to maintain rigidity. Of course they were ignored and the exec. hammered home his “vision.” This resulted in some heavy scrambling and long nights to perform damage limitation on this far-too-late decision. As a result the chassis was reinforced in key areas to attempt to minimize flex but sadly the design had been fundamentally compromised.
The results of this were several fold. It left the car not as rigid as it should have been, which worked with the stiff suspension to make the car very harsh and nervous. It also gave the C4 the somewhat notorious high door sills that make getting in and out of the car awkward and ungainly.
It was pure chance that when the convertible was released in 1986, this last minute rush of changes actually helped and meant that only relatively simple cross bracing was needed for the new model. It has to be said that as much as I love some GM cars, they seem to make them more by luck than by planning.
With all that said, I’d love to see more C4 coverage in Vette!