2006 CADILLAC STS-V: CHASSIS
Ready for the Track of Autobahn

Performance Division-Tuned Suspension Re-Tuned ZF Steering Gear Larger Wheels, Tires, Brakes Vehicle Launch Control

DETROIT- While carrying the virtues of sophistication and elegance expected by today's discriminating high-performance luxury car buyer - the 2006 Cadillac STS-V has also been developed to be fully capable on the race track through precision tuning of chassis componentry. True to GM Performance Division objectives, the STS-V exhibits significant improvements in forward and lateral acceleration as well as deceleration. Engineers anticipate zero-to-60 mph times of below 5.0 seconds. All this in a seamlessly integrated vehicle with abundant, usable low-end torque and a fully automatic transmission.

Chassis modifications on the STS-V include:

Vehicle Suspension

STS-V Slicing Through the Corners with Grace and Agility

To lower the vehicle's center of mass, engineers lowered the STS-V engine by 14-millimeters from the base STS V-8 engine position. This change also improved driveline angles despite shortening of the two-piece prop shaft. The front subframe required reinforcements optimized for the increased lateral loading to manage the increased torque of the engine. The rear subframe takes on an even greater load from torque and cornering. Engineers added mass-optimized reinforcements at differential mounting points as well as control arm interfaces. An increased diameter tubular front stabilizer bar (36-mm) coupled with an increase in front spring rate (75 N/mm) manage the added weight transfer from increased braking and cornering forces. Correspondingly, the tubular rear stabilizer bar rate was increased (25.4 mm) to balance vehicle understeer. Rear spring rates (80 N/mm) were raised to achieve a balanced ride feel. Specifically tuned monotube shock absorbers manage the increased tire and wheel masses and smooth out road disturbances. A Nivomat leveling system adjusts ride height with load and provides increased spring rate and increased damping as the load is increased. Specific cradle and bushing tuning enhances the smooth transition feel between moderate and aggressive driving.

Steering
A specific, faster 17.2:1 steering gear is included in the chassis tuning package to increase the steering sensitivity and responsiveness, but by using a ZF variable ratio steering gear engineers maintained high-speed stability in avoidance situations. A vehicle-specific steering valve profile effort provides sufficient feedback at speed while maintaining low parking efforts. Additional changes in profile were required to balance the more aggressive front tires. A specific high-capacity steering cooler reduces the potential for loss of system performance during track operation.

The Large Wheels and Brembo Brakes Found on Every Corner of the STS-V

Tires and Wheels
To connect the power to the ground, the rear tires grew to P275/40R19 and are mounted on aluminum alloy 9.5-inch wheels. To reduce the spindle offset on the front steering wheels, and thus improve resistance to road-induced steer, the front tires are P255/45R18 and mounted on 8.5-inch alloy wheels. This provides balanced overall vehicle understeer and exceptional traction to manage the increased power output of the engine. The STS-V rides on run-flat Extended Mobility Tires (EMT) from Pirelli.

Brakes
The STS-V is equipped with 355-millimeter diameter, 32-millimeter wide vented front cast iron brake rotors and 365-millimeter diameter, 28-millimeter wide vented rear cast iron brake rotors supplied by renowned Italian high-performance brake system manufacturer Brembo. The four-piston calipers feature 77 square centimeters of pad area on the front, and 51.5 square centimeters of pad area on the rear caliper. The selection of a specific pad material required balancing of noise and wear characteristics for both the street and the circuit.

Chassis Controls
The four-channel StabiliTrak chassis control system has been recalibrated for the vehicle's increase in horsepower and torque and provides enhanced stability control, especially on low-coefficient surfaces (i.e. snow or ice). In addition, the system allows the driver to select from four modes:

Traction and Stability control on;

Traction control off, and Stability control on;

A performance mode, which provides a "less governed" level of stability control for expert driving

Both Traction and Stability control off.

Vehicle Launch Control
With the increase in torque and the desire to optimize straight-line performance, a specific combination of traction control, torque management and driveline disturbance mitigation was required. The unique logic and prioritizing of system events has led to dramatic improvements in performance while reducing negative feedback to the driver.This Vehicle Launch Control feature software tool is a fundamental building block to a refined, effortless driving experience that has successfully tied together multiple control systems.

Optimized Engine Mmounting

The STS-V in its Natural State - On the Track

With increased engine torque and hotter thermal environment, the STS-V required engine mounts using EPDM (Ethylene Propylene Diene Monomer). This special elastomer meets all performance objectives in a more hostile thermal environment. The mounts have specific tuning to manage the increased loads imposed by the powertrain while ensuring the isolation expected in a luxury sedan.

Shock Tower Brace
To enhance steering precision, a tubular structure runs between the shock tower caps, under the hood and above the engine compartment. The hollow steel brace, which is a common application in high-performance sports cars, brings superior cross-vehicle stability to the front of the STS-V as well as enhanced steering precision and responsiveness.

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