Toyota Hopes Dynamic Suspension Boosts Land Cruiser

Debuting on the new '08 Land Cruiser SUV is a suspension system that Toyota Motor Corp. hopes will give the new off-roader an edge over the competition.

Designing the vehicle to be both “manageable and predictable” in on-road conditions and a good performer off paved roads was a challenge, says Dave Lee, senior product education and development administrator for the University of Toyota.

Stabilizer bars help keep a vehicle flat on the road, especially in turns, but they can be a hindrance on uneven trails by preventing tires from making contact with the ground.

“Over the years I've bumped into many people out there on the trail who, before going onto the trail, simply unbolted their stabilizer bars and left them home in the garage,” Lee says.

That challenge to retain the stabilizer bars while allowing for greater suspension stroke is what led Toyota to develop the Land Cruiser's Kinetic Dynamic Suspension System.

“(The Land Cruiser) has a front stabilizer bar and rear stabilizer bar, like you would with any modern SUV,” Lee says. “But the stabilizer bars are linked together via hydraulic piping and the center control cylinder, (which is) up along the frame rail.”

There also are front and rear hydraulic cylinders, and when there is an imbalance of pressure in them, such as in an off-roading situation, they will move in the reverse direction from one another.

The mechanism “effectively disengages your stabilizer bar,” Lee says, by allowing it to flex a little. This disengagement is made possible because the stabilizer bars are jointed, leaving each side to move independently of the other.

In normal on-road driving conditions, the hydraulic pressure most likely will be equal and the cylinders will not function, leaving the stabilizer bars intact.

“We believe it to be the best of both worlds,” Lee says of KDSS, pointing out it is similar to the computer-controlled suspension on the current Lexus GX 470, also dubbed KDSS.

The new double A-arm front suspension, replacing the previous Land Cruiser's torsion-bar setup, allows for wheel travel of 9.1 ins. (230 mm) from 7.9 ins. (200 mm).

Maximum suspension articulation is 27.6 ins. (700 mm). In the rear, which boasts a 4-link coil-spring setup with lateral control rods, wheels move 9.5 ins. (240 mm).

“We have about 4 ins. (102 mm) of additional total articulation with this suspension over the previous model,” Lee says. “One of the ways that I judge a vehicle's off-road capability is its ability to keep four tires planted on the ground. The better we can do that, the less traction control or locking differentials you would need.”

KDSS is totally mechanical, activating when it senses a wheel has dropped.

For the next-generation of the Land Cruiser's luxury twin, the Lexus LX 570, Toyota has said it will employ an “electro-mechanical” suspension system.

“More than the hydraulic aspect of the LX suspension, there (are) four points that work cross-wise and together in different ways,” Land Cruiser Assistant Chief Engineer Toshihiko Kanai tells Ward's. “That's the main point of the LX suspension. It's as good as KDSS. It's a really fantastic, advanced system.”