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fredmeister fredmeister is offline
Smart quod bastardus
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Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Originally Posted by 911st View Post
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?
In fact I am an I that obvious?....joking.
You know you're right, what youre saying is that you need to consider wheel rates acting thru all the lever arms and distances. I am a little lazy to start measuring all the lever arm and other stuff and was looking for an easy way out based upon others experiences. To do this right on your own would require running alot of kinematic equations and stuff, but if only some of the club racers would tell us the specs on their rides we could avoid alot of experimentation.
I have got Smart racing bars on my car and found their site to have pretty good info on set-up options. Currently I have front 27 sways and 31 rear with the adjusters set more or less mid point on both ends. Running with stock torsion bars and bushings right now at US ride height. My thinking was that reducing roll via large sways is a good start till I can afford to add torsion bars and bushings to make the thing killer on track DE days.
I just don't get the results on lowered track times that I expected when adding the sway bar mods over running the car one season bone stock. My ego is still sore.......running out of excuses if the torsion bars don't make a big difference.
Another option is to switch the front and rear sway bars to get 31 front 27 rear since Smart bars you can do that....though don't want to do it until sure it is the right move.

1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 02-24-2009 at 11:01 AM..
Old 02-24-2009, 10:57 AM
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