Comparison Tests
The tradition of sports-car automaking in recent history has been to turn out a roadster, wait until sales slip, then produce a hardtop to pick up the slack. To the nonenthusiast driver, the idea of turning a perfectly good convertible sports car into a hardtop coupe must seem as pointless as the plot of the film Snakes on a Plane. Why give up the joys of driving alfresco to permanently insert yourself into a rolling phone booth, especially if it costs about the same as the ragtop? But adding a roof to a convertible makes sense to car enthusiasts, because the roof increases structural rigidity that in turn allows for a sportier chassis.
In general, a stiff structure leads to a car that is more precise all around, as everything that is intended to move on a car (wheels, suspension, steering) works best when it is attached to a structure that moves about as little as a line at the DMV. Bolt a terrific chassis to a less-than-rigid platform, and movement in the structure will introduce unpredictable motion and inexact wheel control that will muddy handling. Stiff springs, often found on sporting cars, only exacerbate the motion in a flexing structure. Similarly, a floppy structure will introduce imprecision to the steering system, potentially degrading feel and accuracy.
The Porsche Cayman S and the recently introduced BMW Z4 M coupe are hardtop versions of the Porsche Boxster and BMW Z4 M roadster, although Porsche takes exception to that assessment and wants the Cayman considered as a completely separate model line. Delusion aside, the Cayman S and the M coupe are in the grand, olden-day tradition of the MGB GT coupe and Triumph GT6, trading open-air motoring for a distinctive look and the dynamic benefits that come from increased structural rigidity. Indeed, Porsche claims the hardtop Cayman S is 100 percent more rigid than a softtop Boxster S. Both deliver on the promise of the coupe née convertible by offering a driving experience that is different — more sporting and track-ready than that of their cloth-top brethren.
For the hardtop Cayman S, Porsche charges $4200 more than the price of the convertible Boxster S. BMW, though, charges $2000 less for the M coupe than the convertible M roadster. We can imagine that more than a few customers have walked into a Porsche dealership and balked at the idea that the fixed-roof car costs more than the ragtop. Porsche points out a significant fact: The Cayman S has a larger, 3.4-liter engine and 15 more horses than the Boxster S. But pricing the Cayman above the Boxster does separate the driving poseur from the purist.
At this point you're probably wondering when we're gonna insert the 400-hp Corvette into this comparison test. No, the Vette remains in the wings because Corvette coupes all have removable targa-style roofs, whereas our two Germans have fixed roofs. If you're thinking a Z06, which has a fixed roof, would fit in with these coupes, we'd argue that its 505 horsepower puts it in a different league. Arbitrary, you say? Well, you and tech director/Corvette drooler Larry Webster should get a room. In any event, the Corvette isn't here, so it's Germany versus Germany, BMW versus Porsche. And after a week comparing the Cayman S and M coupe, we've discovered that although both are spawned from roadsters and offer nearly identical performance, it was easy to choose a winner.
