Toyota Motor Corp have adopted a double wishbone type rear suspension for its new Lexus SUV models, "RX350" and "RX450h," to reduce the protrusions of suspension mounts into the luggage compartment.
The RX350 was released Jan 19, 2009, in Japan, and the RS450h will debut in April.
The Lexus RX is the successor of the "Harrier" and the "Harrier Hybrid" and employs the "K platform," which is intended for large front-engine front-drive (FF) vehicles including the "Camry" and the "Avalon."
However, the K platform has so far been combined with a strut type rear suspension, and, therefore, the new Lexus RX models are the first K platform vehicles equipped with a double wishbone type rear suspension.
The Lexus RX is one of the Lexus brand production cars, and 100,000 to 110,000 units are manufactured per year, including the Harrier models. About half of them are for the North American market. And Toyota found that users in the North American market want the vehicles "to be easy to use" and "to keep the current size."
In the existing vehicles that use a strut type rear suspension, suspension mounts significantly protrude into the luggage compartment because coil springs are mounted around the dampers. By using the double wishbone type rear suspension, the coil springs were separated from the dampers and located under the floor, reducing the protrusions.
The width of the luggage compartment was increased by 152mm from the previous models at the narrowest area. And the rear end of the luggage compartment, which has the longest width, was increased by about 30mm by optimizing the structure between the lining and the surface board.
The double wishbone type suspension adopted by the new Lexus SUVs is composed of one trailing arm, one upper arm and two lower arms. This structure is equivalent to that of the double wishbone suspension mounted on the "new MC platform," which was employed by the "RAV4" and the "Vanguard."
The new MC platform has dampers and springs mounted separately, and this idea was adopted by the K platform to increase the capacity of the luggage compartment. Following the adoption of the new suspension, the underbody (in the rear of rear seats) was newly designed.