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Thread: Sway bars

  1. #1
    Senior Member platas's Avatar
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    Question Sway bars

    I need some help here, i want to put some bars, first, wich are the best ones, adjustable,
    second, what should i put in front, 22 or 19, and for the rear ?
    i want my car to be stiff, and i am lowering it, putting some konis, sport adj.

    thanks


    santiago

  2. #2
    Goldmember ttweed's Avatar
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    You could do worse than go thru Chuck Moreland at Elephant Racing for your suspension needs. I believe he uses some of the Tarrett Engineering adjustable swaybars on his car, although there are many people who say you cannot beat the Smart Racing setup.

    Your choice for swaybar sizes is very much dependent on your use of the car, your handling preferences, and the rest of your setup (torsion bars, wheel and tire sizes, alignment, etc.) Call me cheap, but I have had good success with non-adjustable factory ARBs, using 18mm F and R bars on my '67S, w/ 205 tires all around. On my more agressive '73 track car, I use a 19mm Weltmeister adjustable in front and a 22mm Carrera factory non-adjustable bar in the rear, with 8 & 9" Fuchs running 245F and 265R tires.

    "Stiffness" to me is more a function of torsion bars and shocks than of swaybars, as all the anti-roll bar does is inhibit body roll by transfering loads to the opposite side of the car.

    TT
    Tom Tweed
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  3. #3
    Quote Originally Posted by platas
    I need some help here, i want to put some bars, first, wich are the best ones, adjustable,
    second, what should i put in front, 22 or 19, and for the rear ?
    i want my car to be stiff, and i am lowering it, putting some konis, sport adj.

    thanks


    santiago
    Santiago:

    You'll get a LOT of opinions on this subject, but if your car is NOT a race car and you have the same width wheels at all four corners, I would suggest 19mm adjustable swaybars on the front & rear for a balanced setup with good ride quality. That offers plenty of adjustment to tailor the car's handling to your skills and preferences.

    IMHO, 22mm bars make the ride quite choppy on these lightweight cars so I only use those on the '78 and later 911's.

    Just my 2 centavos,
    Steve Weiner
    Rennsport Systems
    Portland Oregon
    503.244.0990
    E-mail: porsche@rennsportsystems.com
    http://www.rennsportsystems.com

  4. #4
    Steve:
    So true........

  5. #5
    Quote Originally Posted by ttweed
    "Stiffness" to me is more a function of torsion bars and shocks than of swaybars, as all the anti-roll bar does is inhibit body roll by transfering loads to the opposite side of the car.
    TT
    Tom:

    With all due respect, "stiffness" is comprised of shock valving, spring rates, and swaybar diameter (settings),....

    Swaybars, being simply transverse torsion bars, do indeed have an impact on ride quality. All you have to do is install a set of 22mm bars on a car followed by a set of 18mm or 19mm ones. The difference is quite apparent.

    We've removed a fair number of 22mm bars on these early cars that their owner's mistakenly installed in the quest for good handling without compromising ride quality. After installing either a pair of 18mm factory bars or 19m adjustable ones, every person was a lot happier with the end result.

    Again, this is in context of the '69-'74 cars that are light.
    Steve Weiner
    Rennsport Systems
    Portland Oregon
    503.244.0990
    E-mail: porsche@rennsportsystems.com
    http://www.rennsportsystems.com

  6. #6
    One of the few smart things I did in my life, P-car wise, was to say to Jeff Gamroth: "Just make it a car you'd like to drive on the street."
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
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  7. #7
    Goldmember ttweed's Avatar
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    Quote Originally Posted by Steve@Rennsport
    Tom:

    With all due respect, "stiffness" is comprised of shock valving, spring rates, and swaybar diameter (settings),....
    We may as well add tires into the equation then, too, as they contribute to the suspension "stiffness" as well, according to their relative compliance. I have felt a huge change in ride quality from low aspect ratio tires vs. high aspect ratio. If we're talking about ride harshness, we better throw in unsprung weight as well.

    Swaybars, being simply transverse torsion bars, do indeed have an impact on ride quality.
    Yes, they do impact ride quality, but is "stiffness" really the quality they effect? I think your description of "choppiness" fits better. With all due respect , an anti-sway bar is not a "transverse torsion bar" in the same sense as the other torsion bars are in a 911, as it is not fixed at one end to the chassis, it is coupled to the opposite wheel. It does not effect the spring rate in the same way at all. When vertical forces act on both wheels at the same time, such as in straight line braking and accelerating, or going over a speedbump at right angles, there is no increase in suspension "stiffness" or spring rate at all from the ARBs, other than the slight friction of the bushings connecting it to the car. To my way of thinking, "stiffness" should be applied to those things that increase the wheel's resistance to movement in all situations, like shock valving, spring rates, tire aspect ratio, and even unsprung weight. ARBs only come into play when one wheel is acted on differently than the other.

    When a single wheel falls in a pothole, and the other wheel remains level, yes, there will be increased "stiffness" in the vertical motion of that wheel (because of being coupled to the other wheel with the bar), which results in a harsher transfer of energy to the cabin from the bump and can lead to the perception of "choppiness" in the ride quality that you describe. To me, "stiffness" and "choppiness" are two different qualities. I guess it is really a matter of semantics and how you define the terms. "Stiffness" (to me) is a constant that happens in all situations. "Choppiness" is something that happens some of the time, in certain situations, usually related to bumps.

    I do completely agree with your assessment for street cars-- the common road surfaces we have to travel in many places are so rough and potholed that large ARBs can make for a jarring ride, and we rarely drive thru corners at the limit, inducing excessive body roll, which is what they are designed to correct. On a smooth track, however, they can be a very effective performance enhancement in cornering, by limiting body roll, with resulting camber changes to the tires, and increasing lateral weight transfer. It's a matter of how you will use the car, and what your "ride comfort" tolerances and expectations are.
    Tom Tweed
    Early S Registry #257
    R Gruppe #232
    Rennlist Founding Member #990416-1164
    PCA National DE Instructor
    Read my surf novel!

  8. #8
    Quote Originally Posted by ttweed
    It's a matter of how you will use the car, and what your "ride comfort" tolerances and expectations are.
    Without a doubt, wise words, Sir.
    Steve Weiner
    Rennsport Systems
    Portland Oregon
    503.244.0990
    E-mail: porsche@rennsportsystems.com
    http://www.rennsportsystems.com

  9. #9
    Defender of the Normal John Fusco's Avatar
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    What was the logic behind the factory selling the stock (and rally setup, for which it is understandable ) 67S with 16 rear and 15 front sways ?
    Doesn't that setup favor oversteer on an already tail happy car ?

    John

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  10. #10
    Senior Member platas's Avatar
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    Thank you guys,
    i am runing 205/55/15 toyos, but i like the stiff feel, the go kart feeling.
    Now does it matter if its a 71, since the earlier years are shorter and lighter?

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