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interesting thread. I know that a formula one suspension is about as applicable to a 911 as an off=road racer, but both are extreme examples of high roll centers, dictated by the parameters of the vehicle they are mounted on, particularly F1, where higher noses have raised the rollcenter above the COG, from what I can tell looking at one. I assume jacking is limited with shock rates, roll stiffness(spring or sway bar), etc.
what is the reason that prior to the limitations set by the aero advantage of a higher noses, most race cars were designed with a very low roll center(-2 to +1")?
to minimize weight transfer caused by loads being transmitted through the arms(jacking). this low roll center design is not practical on a strut car though, with a fairly fixed strut angle. In order to get enough camber gain to compensate for the body roll, the roll center must be raised, since we have no upper arm to move the pivot point downward. I think Porsche pretty much got the roll center right at the factory hieght for the tires they came with, but to maximise performance with a tire like a hoosier A6, more camber mid turn is needed, adjusting the roll center back to stock after lowering, helps considerably at keeping the camber close to where it needs to be, But I suggest doing whatever possible to increase camber gain to more than stock, to allow statick camber to be minimised, to keep the tires in good contact under braking. this works best if you can do it front and rear equally.
Another problem with the swingarm rear suspension is that the roll center moves a lot. see picture of triumph earlier in thread for extreme example. for this reason, it may not be a good idea to raise rear roll center too much, so more static negative camber in the rear is usually needed than in the front.
I am trying to lower a 986 boxster while maintaining or increasing camber gain. I know that the 996 GT3 RS has taller spindles for this. Does anyone know what other components are needed with the spindles?
i.e., when using the GT3 spindles, can stock 996 calipers, hubs and rotors be used without modification, or are the offset for hub and rotor, and caliper transferred to a different mounting for the calipers, requiring all the parts to need to be used together.
If anyone has tried to upgrade a 996 to gt3 brakes, and been able to use stock spindles, then the swap should work the other way as well.
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