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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Quote:
Originally Posted by fredmeister View Post
I agree and appreciate all the data 911ST.
My question perhaps was not as clear as I wanted. I just wondered why the recommendation of a significantly stiffer front sway bar than rear sway bar. I would suspect that since the torsion bars are matched to the 930 weight distribution 40/60 why not run equal sway bar rates or possibly bias a stiffer sway bar rearward?
I know the stiff front bar would bias toward under-steer, but if the torsion bars are so well balanced wouldn't such a big stiffness difference for the front sway bar lead to excessive push?
I have spent some time thinking about it and I think it has to do with the geometry of how the sway bar levers interact with the front and rear suspension.

If you look closely the rear is a single lever that is hinged not to far from the torsion bar center line so in effect the TB is basically operating on apx an 18" lever (bar CL to axel).

The front however is two levers compounded or acting in each other. There is the short arm from the torsion bar CL to the end of the bar and it restest in about the midle of the second arm that runs between the TB center line and the wheel center. Thus, the front has compound levers require more force to exert less sway bar force at the wheel.

Also note that a car with wider track like a turbo increases one of these two levers which actually reduces the front spring rate over a normal width 911 with the same spring rates.

I know you have an engineer's mind. Please think this through or digram it and see if you come to the same conclusion?
Old 02-23-2009, 10:15 AM
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