To many suspension designers, double wishbones are the ideal suspension. It can be used on front and rear wheels, it is independent and most importantly, it has near perfect camber control. For over 40 years and even today, this is the first choice for racing cars, sports cars and High end Saloons
Basically, double wishbone suspension always maintains the wheel perpendicular to the road surface, irrespective of the wheel's movement. This helps to ensure good handling.
Traditional double wishbones consists of 2 parellel wishbone arms of equal length, which has the drawback of excessive tire scrubbing because of the large variation in track width as the wheel moves off the neutral position.
Therefore engineers developed
unequal-length non-parallel A-arms to
solve this. By tilting the upper A-arm, anti-dive function can also be achieved.
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Double wishbone suspension has been very popular in American cars. But not so much in Europe because cars are smaller and thus cannot accommodate this relatively space-consuming type of suspension. It is also more costly than MacPherson struts and torsion beams because it involves more components and more suspension pick up points in the car body. For to these reasons, very few smaller cars adopt it. Honda are one of the few makers who try to make heavy use of it. (See pictures below)
So do American cars handle better then european ones. I think not, but this is more down to the size, weight, suspension settings, than any neglect in the design department. |
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Equal length and parallel to each other.(Diagram from the Competition Car
Suspension book) 
Unequal length and converging. (Diagram from the Competition
Car Suspension book) 
From racing it was learned that the best set up is unequal converging wishbones. Many road cars use this set up but there are one or two variations.
Double A-arm suspension with the spring and damper in the "coil over oil" set
up and is attached to the upper of the two A-arms and to the chassis.
(Diagram from the Suspension Bible) 
Double A-arm suspension with the spring and damper in the "coil over oil" set
up and is attached to the lower of the two A-arm and to the chassis. This is the
more popular set up as the system is far more compact. (Diagram from the
Suspension Bible) 
In F1 the aerodynamic element means that the springs are confined to inside
the monocoque chassis. To do this two systems were designed where the spring was
compressed or extended using as bell crank lever.
Some designers preferred the push rod system. In this there is a connecting rod under constant compression which is attached to the bell crank and also to the bottom of the wheel spindle. When the wheel raises the rod then pushes the bellcrank up which then compresses the spring.
Other designers preferred
the pull rod system. In this there is a connecting rod under constant
compression which is attached to the top of the wheel spindle. When the wheel
raises it pushes the bell crank down which then extends the
spring.
Another advantage of a bell cranked system is that the crank can be arranged to give a rising rate of compression to the springs. Theoretically this can give a supple initial movement (and ride), rising and stiffening as the suspension is worked harder, for better handling.