- Nov 12, 2007
2008 Porsche 911 GT2 introduction: Suspension technology
At the GT2's North American introduction, we had the opportunity not just to try out the hardware on the track, but also to discuss it in detail with GT2 Product Engineer Carsten Schebsdat and Porsche Motorsports head Hartmut Kristen. These gentlemen were in the pits with some examples of their work, and described the subsystems with all the enthusiasm of a proud parent.
Live Photos Copyright ©2007 Eric Bryant / Weblogs, Inc.
The GT2 was developed at Porsche Motorsport, instead of going through one of Porsche's standard product engineering groups. The basic architecture of the 911 Turbo had to remain intact; fortunately, it's a damn fine set of components to use as a starting point.
The rear suspension starts off with a multi-link control arm configuration affixed to a pair of massive cast-aluminum abutments. An aluminum crossmember links the two sides; this is changed from the steel component used in the 911 Turbo, as the absence of AWD in the GT2 changes the loads carried by this component.
Camber gain totals about 3 degrees over the GT2's rear suspension travel of 120mm (about half of this travel is used for compression, while the other half provides droop). A small amount of toe-in - about 1.5 degrees - is added as the suspension compresses; this decreases the slip angle of the rear tires and thus adds stability at the limit (a good thing, given the reputation of older versions of the 911). Static adjustments of camber and toe are handled via a pair of eccentric bushings on each side.
The tightly-wound upper coils of the rear spring are there to provide just a bit of preload when the suspension is at full droop. Otherwise, the short, stiff spring that would be dictated by the engineers' desired spring rate would result in a coil that just rattles around as the suspension is unloaded.
Notice the blue color of the suspension hardware, which is electroplating that is intended to resist corrosion. Don't mistake this as being merely a nice touch on an extremely expensive car; it's necessary to prevent issues related to the use of steel fasteners in aluminum castings.
The front suspension uses a relatively straightforward McPherson strut arrangement. Camber gain is similar to the rear suspension, while a slight amount of toe-out is added as the suspension compresses to further improve stability.
A closer look, however, shows that the front damper is mounted in the inverted position. Although this slightly increases the unsprung weight, the advantage is that the spindle can be clamped to the fat outer tube of the damper - thus increasing stiffness and decreasing camber change under lateral deflection. The spring perch is threaded to change the ride height; there is a second ring that establishes the clamping height of the damper in the upright, but this is not intended to be used as an additional adjustment.
The steering rack is mounted in front of the axle centerline, presumably to yield more room for the front seat footwells and pedals. Also visible here two of the hoses for a front-mounted cooler.
Both the front and rear subframes of the GT2 are attached with metallic bushings, where as the Turbo uses rubber. This creates a slight NVH penalty, but improves the responsiveness and road feel of the car.
The roll rate of the sway bars can be adjusted via a trio of endlink mounted locations. Both ends of the vehicle offer this option; we'd suggest altering the front-rear balance of the GT2 at your own risk.
The huge 15" ceramic-composite front rotors are clamped with radial-mounted one-piece forged six-piston calipers. The calipers mount to the uprights using the so-called "radial" orientation, which results in less deflection between the two components during braking.
The rotors are formed with holes and directional cooling vanes, and mounted to aluminum "hats" for a weight reduction of nearly two pounds per corner. The grayish-blue coloration is due to the anti-corrosion coating - made necessary by the use of steel hardware. Plain ol' steel is used for the hats out back, as those parts need to transmit torque from the halfshafts to the wheel lugs.