macpherson, double wishbone?

[silvia15]

i have a suspension question, i know that macpherson and the double wishbone are both different race inspired suspension set ups, but what is the difference between them and normal suspension and what are the difference between each other, also why do they call them what they do?

[curtis73]

A slight correction. Struts are a space and weight saving design. Although they have their place in certain racing classes, they are by no means race-inspired.

A double wishbone usually adds a touch more weight, but using exotic metals the weight can be shaved off. A double wishbone's biggest strong point is its extremely variable configuration. Using different geometry you can make roll centers, instant centers, and other factors like kingpin inclination in all sorts of configurations. The other big benefit is that its dynamic. Since there are three planes, two axes, and two pivots, the camber and caster curves can be tuned almost infinitely. With a strut, your arc of travel is relatively fixed and difficult to alter.

I wish I had some links to photos for you, but I can't seem to find any. If I find some I'll post them.

[CraigFL]

The wishbone suspension:

http://encyclopedia.lockergnome.com/...one_suspension

The McPherson Strut suspension:

http://encyclopedia.lockergnome.com/...cPherson_strut

[MagicRat]

Further to Curtis points,
The wishbone suspension changes camber as it travels through its arc, which has benefits in modifying and partially correcting handling problems inherent in cars when they go around corners, such as body roll.

Strut suspensions generally do not do this.

Generally strut suspensions are an inexpensive way to achieve independent suspension and is better than live axles (front or rear) which often are even cheaper than struts.
Wishbone suspensions are generally more expensive than struts, but more sophisticated and have the potential to provide better handling.

[curtis73]

At the risk of being vague, I also have to add to my own post. Dramatic handling CAN be achieved with both types; I had a BMW e30 (80's 3-series) that exhibited some of the finest stock handling I've ever experienced with a strut front and an uninspired rear design. When I say that struts are not race-inspired, that doesn't mean they aren't competent, its just that they lack two main performance qualities; 1) they can't be modified very much without making odd handling qualities, and 2) they respond best to very tight suspensions that don't flex much. Within the range of travel, a strut suspension exibits less than ideal characteristics. A double wishbone suspension is easier to tune.