Spring 2010 Forward to a Friend

Independent Rear Suspension
Wishbone Suspension

THE EXCELLENT RIDE AND HANDLING PERFORMANCE PROVIDED BY EVERY SUBARU IS DUE IN PART TO ITS INDEPENDENT REAR SUSPENSION. SO WHAT DOES THAT MEAN?

A vehicle’s suspension system holds up the body structure. It also determines how the wheels encounter the surface that the vehicle is traveling on. There are a number of components involved: tires, wheels, springs, shock absorbers, and often a series of metal links between the body or frame. These suspension components not held up by the vehicle’s springs represent its unsprung weight.

Solid VS. Wishbone Suspension Diagram

SOLID CONNECTION

To appreciate today’s Subaru suspension, consider how the majority of automotive rear suspension systems used to be designed. They had solid (also called live) axles, meaning that the rear wheels were connected by a tube that housed the axle shafts in rear-wheel drive vehicles. In front-wheel drive vehicles, solid rear axles without axle shafts connected the rear wheel assemblies. Solid-axle design still is employed in some vehicles.

When wheels are attached to a solid rear axle, they move together in response to the road surface. If the right wheel moves up, it tips the axle, thereby tipping the left wheel, and vice versa. The axle of a rear-drive vehicle includes the rear driveshaft, so that weight is carried in the axle’s movement.

INDEPENDENT BY DESIGN

A rear suspension that allows a wheel to move up and down without affecting the wheel on the other side of the vehicle is said to be an independent rear suspension.

The rear differential of a Subaru is attached to a rear subframe. The various links that hold the wheel carriers to the vehicle also are attached to that subframe.

Instead of an axle across the width of the vehicle moving in response to the wheels’ contact with the road, the wheels move vertically, guided throughout their vertical movement by the links. Because they are not attached by an axle, the wheels are independent of one another. One side can bounce down the road while the other remains flat.

Subaru utilizes a double-wishbone link design. The name originally was derived by the shape of the links – that of an animal’s wishbone. The two ends of each wishbone attach to the subframe, and the middle attaches to the wheel carrier. Today, wishbone-type links don’t always have the shape of a wishbone, but the concept of two attachment points to the frame is still there.

THE BENEFITS OF AN INDEPENDENT REAR SUSPENSION

An independent rear suspension results in many benefits. Vehicles with such a design ride smoother than their solid-axle counterparts. These suspensions also permit finer suspension tuning, with components designed to provide specific handling characteristics. The wheels can be aligned accurately for crisp and predictable turns, high-speed stability, and/or the capability of handling rough road surfaces.

Subaru independent rear suspensions are designed to have a low profile in a compact design that does not intrude into the cargo area. The interior benefits by having more space and flatter load surfaces in the cargo area.

By engineering light suspension components, the suspension system functions with reduced unsprung weight. That makes it far more responsive to road surfaces, helping to keep tires in contact with the road for improved handling and control.

Overall, an independent rear suspension contributes to improved handling, greater control, and enhanced comfort. And every Subaru has one.