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Negative side effects of anti-sway bars

Discussion in 'Ferrari Discussion (not model specific)' started by Auraraptor, Jan 17, 2004.

  1. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,470
    MO
    What are they? I once heard someone tell me that it overstressed the top of the strut tower, forcing replacement or something like that. Can some one explain? It seems to be an inexpensive way to decrease roll.
     
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  3. FormulaRacer

    FormulaRacer Formula Junior

    Nov 18, 2003
    261
    Are you talking about Sway bars or Strut Tower braces? Sway bars do not go on the top of strut towers, thats a strut tower brace. Sway bars are an entirely different part, and have an entirely different function.
     
  4. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,470
    MO
    Sorry strut tower.
     
  5. mk e

    mk e F1 World Champ

    Oct 31, 2003
    11,651
    The twilight zone
    Full Name:
    The Butcher
    What ferrari has struts???
     
  6. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,470
    MO
    I just did some research and you are right, none that I know have struts. I ment it as a general automotive question and thought I would get the best response here. :p
     
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  8. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,185
    Ok, lets go back and see why we want/need a swaybar in the first place.

    Weight transfer theory tells us that all forces react through only a few parameters. The center of gravity, the wheel base, the track determine how forces are transfered around the chassis. The center of gravity (height) and the wheelbase determine how much weight is transfered longitudinally. The center of gravity and the track determines how much weight is transfered in cornering.

    So, lets say we had a 3000 pound car with a center of gravity 15 inches above the road surface, with a wheelbase of 100 inches and a track of 60 inches. Under 1 Gs longitudinal of acceleration, 450 pounds are transfered, while under 1Gs of cornering, 750 pounds are transfered.

    A spring will compress more if more weight is transfered. Since more weight is transfered in cornering than in acceleration or braking, the car wants more stiffness to latteral forces. The antiroll bar provides this stiffness.

    With antiroll bars thus chosen, the outside front tire can remain at a constant compression height fron braking into pure cornering, providing feel tot he driver.

    Once a car is balanced, one can trade front to rear antiroll bar stiffness to decrease grip at the stiffer end and thereby control oversteer and understeer. Ride height can be used to fine tune the front to rear balance after anti roll bars have been chosen.
     
  9. TimN88

    TimN88 F1 Veteran

    Jun 12, 2001
    5,032
    Northeast
    Full Name:
    Tim
    Strut tower braces connnect mounting plates of the front struts to increase rigidity.
     
  10. PSk

    PSk F1 World Champ

    Nov 20, 2002
    17,673
    Tauranga, NZ
    Full Name:
    Pete
    Strut tower braces cannot hurt a car causing overstress and thus replacement, as their purpose is to strengthen the car.

    Mitch has also covered the anti-roll bar (sway bar) well and they generally cannot hurt a car. If a anti-roll bar is too stiff it will simply lift the inside wheel and ruin grip ...

    Saying that running a car with too harder springs means that more road forces are transferred to the shell and thus the shell can take a hammering ... hence why old race cars are tired. I think you would have to stiffen a Ferrari considerably to cause this problem, and that would be stupid unless you were going through proper setup procedures to get the right spring rate NOT just a stiffer setup. A car that is running too harder springs will be darty and have less than optimal grip ... :(, ie. keeping the wheel on the ground is what it is all about.

    Pete
     
  11. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    Mitch is entirely correct but left an important bit out.

    Suspension Roll centres and squat/dive geometry have a significant impact on weight transfer, and are the cause of many handling characteristics. They are however, very hard to change on most cars. Ferrari's can be changed, but it does involve tricky parts.
     
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  13. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,185
    Roll centers have NOTHIING to do with weight transfer. Weight transfer is a function of only height of the CoG and the wheelbase and track. Roll centers have to do with the (suspension's) RESPONSE to weight that gets transfered.

    If one designed a suspension where the roll centers were at the height of the CoG, the weight still transfers, but the car does not roll (at all!). Or; if someone designed a suspension where the roll centers were 1 mile below the road surface, it would take BIG springs (think rail road car) to deal with the weight that gets transfered. However, in both cases, the weight that gets transfered is the same! The response is different.

    One, instead, should think of the distance between the CoG and the roll center as a lever. The longer the lever, the more response a given set of springs and antiroll bars will take. With CoGs in the 15" range, and rear roll centers at 4" the rear lever arm is effectively 11".

    It turns out that on modern Ferraris, the rear roll center moves about 50% faster than the rear ride height. So, if you add 2/3" to the rear ride height you will move the rear roll center by 1". This reduces the lever arm associated with the roll center by over 10%! Effectively changing the spring at that end by 10%. This can be a powerfull tool in balancing the chassis for oversteer and understeer or even driver preference. In fact, it is so powerful that most OS/US adjustments are done in the 2-5mm range, 2mm being a small adjustment, 5 mm being a big adjustment.
     

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