McPherson Strut Suspension and Torsion Bar Suspension

Check out this link.

http://www.carbibles.com/suspension_bible.html

If it doesn't answer your question, I cannot...

THANK YOU ITS GREATLY INFORMATIVE.

The link provided by bhrescobar is excellent.

As you can see there, a torsion bar is a type of spring, whereas a McPherson Strut is a type of suspension assembly (itself containing spring or springs), providing a particular wheel dynamic geometry. Although I am not away of a McPherson Strut suspension system that uses torsion bars as the primary springing medium, it would be possible to make one.

Also, the most common use of torsions bars on cars is actually the "anti-sway" or "anti-roll" bar that virtually every car will have at least in the front and often front and rear. In this application they are not called "torsion bars" but that's how the center section is working.

Also, for trivia fans: a coil spring is really a torsion bar, would into a helix. As it compresses, the wire is primarily "twisted", rather than primarily "bent". That is one reason a softer spring has more turns per unit length, and a harder spring has fewer.

A torsion bar is a form of spring. A McPherson strut is an assembly that includes a type of spring as an integral part of the unit (Springing – damping – steering). Think of it like this, a car sits on the spring, whatever it is, and the spring provides the ride height and movement to allow for rough surfaces. A coil spring can allow more free movement then a torsion bar, so the type of spring depends on how much free movement you need. The majority of new road cars will sit on coils. The main application I have seen for torsion bars is on race cars, where you can guarantee a smooth surface so don't need much movement, but do need good control of car body movement. (Torsion springs are stiffer then coils weight for weight) Don't forget damping is separate from springing. I hope this helps, if you have any more specific questions drop me a line, I have done a lot of work on suspension design for racing applications.

The Porsche 911 front suspension can properly be called (modified) McPherson Strut*, but it does not have a coil springs, but rather, torsion bars. I think the key features of a McPherson Strut front suspension are that 1. the damper (or damper housing) rotates as the wheel is steered, 2. that the damper actively controls suspension geometry, and 3. that both king pin inclination and caster angle are determined by the angle of the strut/damper shaft. In all other suspension systems, the damper location has no effect on the dynamics of wheel geometry.

I'd argue that the most common torsion bar application is not on race cars but on the original Volkswagen Beetle, most Porsches, and many Chrysler products. Chrysler's reason for generally abandoning torsion bars for many models had to due with cost rather than ride quality. Torsion bars can provide any reasonable range of wheel motion -- certainly up to a foot or more, well outside the normal range of passenger cars. Even without employing the sort of lever systems seen in race cars and many motorcycles, torsion bars can accommodate a very large range of motion. The everyday proof of this is in the torsion bar spanning the front of virtually every car (the anti-sway bar). This torsion bar accommodates more than the usual suspension travel accommodated by a wheel spring: full droop on one side and full compression on the other.

* Actually, Earl's Name was really MacPherson, but the world seems to have forgotten that.

An example of McPherson with torsion spring I've seen is the Mitsubishi L200 truck, if I'm not wrong. It has a lower strut, the damper in vertical position, serving also as the axle for the wheel steering, but the spring is a torsion type connecting the chassis and the lower strut. Maybe because the truck has a chassis, and not an integral monoblock, so the spring cannot be installed in it... Or the car would loose its wheel cover together with the front suspension in the first hole...

In addition to the torsion spring reference here posted, there's another application: rear suspension semi-independent by torsion bar. This is also a worldwide used type in less expensive cars, that use successfully McPherson in front and semi-independent in aft position. It uses two drag braces that connect the wheel hubs to the car structure mounted in longitudinal position. The damper and the spring coil are assembled in vertical position, as the McPherson does. But there's another large bar connecting the two suspension sides. It acts like a stabilizer bar, but is bigger, with a profile cold formed like a "V" rotated 90 deg from upright position, the size being like 4 inches wide. The result is a behaviour between an independent multi-link type and a rigid shaft one, and is very simple and, as you may imagine, cheap to build. And works very well for those reasonably light cars, despite of its simplicity.