Back on track.....Anti Roll Bar stiffening brackets
The 924 design carried over to the 944 & 968 (Vertical hung brackets) and did not change ? to my knowledge
it was originally designed for the 2.0 application with a 21mm thick bar, 14" wheels and a 1100kg ish vehicle weight
Since we all know this vehicle evolved into 2 more body shapes and had numerous suspension, brake engine interior, & wheel etc..changes
Porsche increased the diameters of the ARB's which upgraded the car's handling in combination with the increase in power & weight and the car's increased cornering and top speed capability.
Every time the ARB diameter was increased this added more torsional stiffness across the axle and effectively the ARB Spring offered
more rigidity and less compliance, exactly as it does when many people fit thicker roll bars for road and track use.
Also just the same as when fitting harder material bushings, this increases the actual spring rate (Deflection) of the bar because it deflects less as it does with the softest material (OE rubber). The poly bush manufactures quote an actual spring rate loss of 20% so Rubber could be twice this?
Sway bar stiffness increases as the fourth power of the diameter. For example, a sway bar might have a diameter of 22mm and you are considering changing it for one which is 26mm in diameter. 224 (22 x 22 x 22 x 22) give a stiffness factor of 234,256 units. The second bar’s stiffness is 264 which is 456,976. Divide one by the other and you can see that the second bar’s stiffness is almost twice (1.95 times) as high, even though it’s only 4mm thicker!
So fitting Poly bushes, a thicker bar and these brackets all 3 will produce a decrease in the amount of twisting deflection the bar had originally, which could be too much and cause the car to understeer as the inside wheel is lifting too much and the outside wheel has reached a maximum weight transfer / the camber angle changes and the tyre molecules give up and start to slide, but this can be counteracted by a stiffer rear Bar and shocks and springs.
Racers normally go for as thicker bar as they can, we know the 968 Mo30 option had a 30mm front and 3 way adjustable rear 19mm set up.
Porsche may very well of packaged and designed the ARB vertical brackets to offer some compliance, they are isolated away from the frame and the bush position holding the bar is located a reasonable distance away from the car's chassis frame, but triangulating and stiffening this is no different to fitting harder bushes and / or a stiffer ARB so I did question the facts where the info had come from (mates mates) as I wanted to know more but also from my road and race tuning career and experience I wanted to make a point that fitting such brackets would not make the car a death trap!
(as a few members did express they had no issues with them fitted) any change to the balance can be sorted that's the fun of tuning suspension systems for road and track.
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