ALL NEW CHASSIS FOR LATEST CHEVROLET LUMINA SS UTE

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The new Chevrolet Lumina SS Ute benefits from an intensive 20-month chassis development programme specifically tailored to prove out a demanding set of requirements for the Ute. The benchmark for ride, handling and comfort was the luxury, smoothness and isolated feel of the Chevrolet Lumina SS sedan. The linear handling and steering characteristics of the sedan also had to be retained in the Ute as did the sporty character associated with the previous generation model.

Linear Control Suspension

All of this had to be achieved considering the fundamental load-carrying role of the Ute. Prominent in meeting these demanding requirements is GM’s Linear Control Suspension. Both the front and rear suspensions are a product of an eight year development programme to refine the suspension characteristics of the Lumina sedan and transfer their use across to the Ute to achieve a no compromise balance between ride and handling quality and load carrying capability.

The process of suspension development was aided by the extensive use of dynamic computer modelling tools to achieve the best possible geometry and setup. The result is better lateral grip and a more linear response for an improved turn-in characteristic with less roll-steer evident. Lane change behaviour, particularly under a fully loaded condition, is significantly improved over the previous model.

Electronic Driver Aids

The Lumina SS Ute comes standard with a Bosch Electronic Stability Programme (ESP) that incorporates an anti-lock braking system, electronic brake force distribution, electronic brake assist, and traction control. The system is optimised using a specific set of system calibrations suited to the character of the vehicle and its intended usage.

The brake system is all-new with large diameter discs front and rear. The new system offers better brake pedal feel, increased fade resistance, and improved noise and vibration insulation.

Improved Tyres, Steering, and Chassis

The tyre size has been increased for better all round grip that manifests itself in better cornering grip, improved acceleration, and a shorter stopping distance. The wheel and tyre combination used on the Lumina SS Ute is 18-inch X 8-inch alloy rims fitted with 245/45 R18 96V tyres. A full size spare wheel is provided.

A forward mount position has been adopted for the steering rack to place it in front of the axle centre line. This forward mounting position for the rack provides for enhanced steering performance, a more positive turn-in, and a more precise steering feel and better feedback from the road. A variable ratio gear is used for the steering rack with a 15% change in the ratio from the centre position to full lock. The light steering effort contributes to a more relaxed driving experience

The chassis features a new engine sub-frame design that offers greater strength and stiffness for improved handling and better noise and vibration damping. The new frame design adds torsional and bending stiffness to the front structure that contributes to improved resilience in the event of a crash impact.

The 75 litre fuel tank is positioned under the loadbox floor and ahead of the rear axle. Its saddle-like form allows efficient packaging of the propeller shaft and the exhaust system along the centre line of the vehicle.

A limited-slip rear differential is fitted as standard. This multi-plate clutch system allows for a more progressive characteristic and is tuned for maximum grip out of corners and excellent durability.

The differential unit features double isolation – isolation from the rear suspension sub-frame by rubber bushes at three points, and isolation from the body at four points. The gear set and bearings are improved over those of the previous model.

Extensive Crash Safety Model

The new Chevrolet Lumina SS Ute benefits from the most intensive crash-modelling programme ever undertaken by General Motors in Australia. Research and development for the programme, conducted initially for the Lumina SS sedan, focused on real world driving conditions and covered an extensive range of collision scenarios and occupant protection criteria. This wide range of information was fed into a computer model to allow extensive virtual modelling to be done to prove out the safety configuration of the Lumina SS sedan and Ute.

In the four-year development programme to bring the new Lumina SS Ute to reality GM Australia took a significant step forward in that the Lumina SS Ute early engineering programme was based totally on virtual safety tests rather than actual hardware tests. This did away with the need for pre-production mules and prototype crash test units to be used in physical tests in the early stage allowing for a much more efficient and cost effective early development cycle.

Advanced virtual tools were used to simulate upwards of 1 500 model-specific barrier type virtual crash tests. The accuracy of this process is now such that it was possible to do away with physical tests until the immediate pre-production phase when a comprehensive set of actual crash tests was conducted to substantiate the results of the virtual crash tests.

The process was aided by the significant amount of data available from the Lumina sedan test programme. For the Lumina Ute additional areas of focus were the vehicle’s performance in side and rear impact scenarios. Additional research was also done on frontal impact performance.

The physical crash test routine for the Lumina SS Ute involved five actual barrier crash tests; one frontal, two side-on, and two rear-end tests. The rear impact barrier test, which assesses the integrity of the fuel tank in a severe crash, is a particularly severe one that is conducted to a standard adopted for all GM vehicles globally.

A large percentage of high strength steel is used in the body construction of the Lumina Ute for optimised structural rigidity and sectional efficiency. Advanced type, and ultra-high strength steels, are used extensively in the side structure to protect against intrusion and deformation in the event of a collision. Defined load paths in the chassis provide protection in the event of frontal, side, and rear-end impacts by channelling crash energy away from the passenger area.

Adaptive Occupant Restraint

An adaptive occupant restraint system is featured on the Lumina SS Ute. This system includes dual-stage front airbags together with front seatbelt pre-tensioners and load limiters. The driver and passenger airbags inflate in two stages depending on the severity of the impact and the respective positions of the seats.

The design of the door trim profile has been optimised to provide the best possible side impact protection. To help protect against lower limb injuries to the driver in a severe impact the brake pedal is designed to break away when the release mechanism is triggered by an intrusion into the pedal area. When an intrusion into the pedal area occurs, the brackets of the brake pedal mount will bow outwards allowing the pedal itself to decouple from the mount.

A sliding intermediate shaft is fitted to the steering column to assist in preventing the transfer of engine movement into the steering column. A calibrated ride-down mechanism directs any movement in the column away from the driver in the event of a crash impact.

Powertrain

Power for the Lumina SS Ute comes from a 6.0 litre Chevrolet Generation IV alloy block engine. Maximum power is 270 kW @ 5700 r/min (up 10 kW on the previous model) and peak torque is 530 Nm @ 4400 r/min (up 20 Nm on the previous model). Rear-wheel-drive is via either a six-speed manual transmission or a six-speed automatic transmission with Active Select.

A tap up / tap down function is provided on the automatic transmission. This is activated when the shift lever is moved sideways into the ‘tap gate’, an action that also changes the shift pattern into sports mode. Gear changes can then be initiated by tapping the lever either up or down in the gate. If the lever is left untouched gear shifts will be automatic but the sports shift pattern will be adopted.

When the sports mode is first selected the transmission will shift down one gear in anticipation of the driver requesting a more responsive reaction. Electronic control of the transmission allows for engine braking and for 2nd and 3rd gear starts when tap mode is selected.