A dual ball joint suspension uses a pair of arms, one in tension, one in compression, to replace a wishbone, in a MacPherson

MacPherson strut

The MacPherson strut is a type of car suspension system which uses the axis of a telescopic damper as the upper steering pivot. It is widely used in modern vehicles and named after Earle S. MacPherson, who developed the design.-History:...

 or SLA

Short long arms suspension

A short long arms suspension is also known as an unequal length double wishbone suspension. The upper arm is typically an A-arm, and is shorter than the lower link, which is an A-arm or an L-arm, or sometimes a pair of tension/compression arms...

 suspension. The outer end of each arm terminates in a ball joint

Ball joint

In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles.More specifically, a ball joint is a steel bearing stud and socket enclosed in a steel casing. The bearing stud is tapered and threaded. It fits into a tapered hole in the steering knuckle. A...

, hence the name.

General description

The two arms, the spindle, and the body, form a four-bar link. Careful optimisation of the geometry leads to an effective virtual ball joint outboard of the spindle, which is very useful for a suspension designer, allowing negative scrub radius

Scrub radius

The scrub radius is the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road....

 whilst keeping the ball joints out of the way of the brakes. Some manufacturers use a double ball joint arm to replace both wishbones on a short long arms suspension

Short long arms suspension

A short long arms suspension is also known as an unequal length double wishbone suspension. The upper arm is typically an A-arm, and is shorter than the lower link, which is an A-arm or an L-arm, or sometimes a pair of tension/compression arms...

. This provides further opportunity for optimising the geometry.

Examples

It is used on large cars such as the Lexus LS460, BMW X5

BMW X5

The BMW X5 is a luxury crossover SUV introduced in 1999 as the first generation E53. It was BMW's first SUV also known as "Four-by-Four" in the UK. It features all-wheel drive which is branded as the "X" drive system and is available with either manual or automatic transmission...

, Ford Territory

Ford Territory

The Ford Territory is a crossover SUV built by Ford Australia and based on the EA169 platform of the Ford BA Falcon. It was released in April 2004. Its code name inside Ford was E265. It won the 2004 Wheels Car of the Year award, the reviewers praising car-like handling and practicality as reasons...

, and General Motors

General Motors

General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...

' Zeta

GM Zeta platform

Zeta was the original name for General Motors' full-size rear-wheel drive automobile platform. The architecture was engineered by Holden of Australia and was most recently referred to as the "Global RWD Architecture". The GM Zeta replaced the Australian V-body and was considered as the replacement...

-derived models.

Disadvantages

The extra ball joint adds weight and cost. It also increases steering friction, and the parasitic friction in the suspension. The geometry has some undesirable characteristics that need careful management, such as returnability from full lock when parking.