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I have always thought the VW a arms needed to be even or pointed down but never up.. which limited how low you could get the car. I have lately seen several cars sitting low, the a arms are pointing up and the drivers say they don't have any handling problems. Is the a arm position that important? thanks
They are probably running very stiff springs, 600# or more.
They are referring to bump steer. As the suspension moves up (bump), The arc of the control arm moves the lower pickup point(balljoint) inboard. this affects toe-in as that happens. The remedy is a spacer between balljoint to steering knuckle. In effect this puts the control arm at the max of it's arc which minimizes how much camber/toe change on bumps. Also the tie rods act the same way and need to be parrallel to the control arms. IT class doesn't allow ball joint spacers, but they might have recently allowed tie rod end adjustments... Check the GCR and Fastrack.
I run mine about level with a 1/4" reverse rake and the car really rotates, I think with 700# fronts I could go a little lower with little to no bump steer but thats soemthing to consider later.
Lowering too much gives the cg a larger lever arm to create roll. The point about which the car rotates moves below the ground.
Some folks do counter this with very heavy springs. The - if the suspension can't move it won't do bad things approach.
Others run rally height suspensions and 'preach the gospel' of correct geometry.
The rest of us are somewhere in between because of what we found that works best for our own driving habits, or what we happen to have availalbe to use on our cars.
My car is pretty close to level control arms, maybe a hair past. I run 550# springs and a small front ARB with good success, but may try heavier springs at some point.
My buddies Prod car sits much lower but uses a ball joint spacer to help correct the control arm angle, and runs heavy springs on a very light car to keep it from moving anyway, with great success.
I am of the level a arm set. We have one of the best handling prod sciroccos and the a arms are never up. It is much better to be level. When the a arms are lower you get a lot of rocking that can only be countered by very heavy springs but having done both it is much faster to have the correct geometry.
Chris is correct. This is Shine's philosophy. In addition (though technically related), the camber change curve only works correctly with level A-arms. That is, with level A-arms, the MacStrut behaves more like a doulble A-arm suspension; but, with non-level A-arms, it behaves more like an uncompensated swing axle suspension (think of early Spitfires). Very stiff springs can be used to make it handle more like a solid rear axle. Thus, for pure handling, level arms are best. The reasonable results of those who sacrifice level for lower ride height (often needing stiffer springs) is probably mostly attributable to the better aero of a lower car -- honestly, this may actually work out on very fast tracks, especially with tires that are relatively insensitive to incorrect camber or uneven loading.