Porsche 928 Suspension and Handling
Rear suspension on the Porsche 928 was novel. Road & Track described it as “upper transverse links, lower trailing arms, coil springs, tube shocks, anti-roll bar.” Porsche proudly called it the “Weissach (VEE-sock) Axle,” after the site of the company’s new Development Center not far from Stuttgart.
Its novel suspension and mounting structure gave the Porsche 928 great handling.
Britain’s Autocar noted that each lower arm “takes braking and acceleration torque loads as well as helping the ball-jointed single top link locate the wheel laterally. The bottom [arm] has its inboard pivot axis inclined outwards at the front, like a semi-trailing arm, to provide a measure of anti-squat. And at the front body pivot, it has a sort of double joint [actually an articulated mount]. The give of this in a corner under braking and decelerating forces [that ordinarily result in] an oversteerinducing toe-out [instead] makes the outside rear wheel toe-in slightly [and] thus counters the usual accidental oversteering self-steer in the case where the driver who has entered a corner too fast lifts off, or, worse, brakes.”
Like so many Porsche innovations, the Weissach Axle was an elegant solution to a thorny problem, and it marked a first for toe-compensating rear suspension in a production car. Other manufacturers would devise their own solutions, including full rear-wheel steering, but it would take them at least a decade to follow Porsche’s lead.
ZF supplied the 928’s rack-and-pinion steering, which, unusually for a Porsche, came standard with power-assist. The assist was also predictive in that it varied with vehicle velocity: minimal at highway speeds for proper effort and optimum control, maximum at low speeds for easy parking. Gearing was reasonably quick at 3.1 turns lock-to-lock. Again for better control (and foreshadowing the later 944), negative steering roll (or “scrub”) radius was designed in to counter sudden changes in steering torque in situations like a front-tire blowout.
The 928 rolled in on low-profile, high-performance 225/50VR16 Pirelli P7s mounted on special “telephone dial” cast-alloy wheels. These state-of-the-art tires worked with the high-tech suspension to give the 928 uncanny cornering stick. “They hang on to absurd limits,” exclaimed Autocar, “and combined with the drama-free way the car simply understeers ultimately, it is easy to dismiss the 928 as almost dull in a corner. And then you think about how fast you are going through the corner.”
In fact, the 928 suspension was so remarkably compliant, absorbing most every kind of irregularity, that critics could hardly believe the race-car-like cling in hard driving. “True, those tires are harsh over sharp inputs,” observed Road & Track, “and they’re also noisy on all but the smoothest asphalt surfaces, but otherwise the ride is wonderfully supple and well controlled. The softness of the suspension on our California freeways had some drivers expecting a floaty, wallowy ride on fast, twisty undulating roads. Nothing could be further from the truth.”
The big vacuum-assisted all-disc brakes proved equally capable. They could rein in a 928 at up to 1 g deceleration and, in R&T’s tests, a mere 139 feet from 60 mph. “One wonders how much the very handsome, wide-eyed wheels help in keeping the fade performance good,” added Autocar. “Few cars have such nakedly obvious discs . . .a piece of functional design that makes the car look all the more what it is -- ideally functional.”
Acceleration was nothing less than Porsche-brilliant. Despite its heft, a five-speed 928 would reach 60 mph from rest in 7-8 seconds; the automatic version took perhaps a tick more. The standing quarter-mile flew by in 15-16 seconds with manual, the speedo reading about 90 mph. Top speed was 135-145 mph, more than most owners would typically use.
Not that they didn’t have a right to expect super performance, because the 928 was super expensive, arriving in the United States at a heart-stopping $26,000. “Hardly a bargain,” sniffed R&T in 1978, by which time the price had ballooned to $28,500. “But clever engineering doesn’t come cheaply, and few automotive design teams are more clever than the one residing in
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The Porsche 928 was composed at speed thanks to its smart suspension design.
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