Manual Steering: Ok for a DD?

There's a rampant internet misunderstanding that the relationship of the tie rods to the ground matters to bumpsteer. What matters is the tie rods' relationship to the A-arms. More specifically, the line described by the tie rod pivot points needs to be parallel to the line described by the arm's pivot points, so that they follow the same arc when they move. Bumpsteer comes from the steering knuckle following an arc that has a different pattern than the one the balljoint follows. If you don't change the pivot points' relationship to one another, you don't change the bumpsteer characteristics. The factory characteristics are pretty good to start with, so unless you've radically slammed it, nothing's going to change much as far as bumpsteer.

If all you do is lower the car by shortening the springs, then all the suspension knows is now it's compressed a little more. The bumpsteer characteristics are the same as if you added a bunch of weight to the car and lowered it that way.

If you start changing the underlying geometry, changing the pivot points' relationship by moving the rack up or down, moving the steering knuckle up or down, moving the A-arm mounts up or down, or moving the balljoint pivot up or down, then you've changed the bumpsteer characteristics, because now you've made the arcs different.

Think of it as a parallelogram when looking at one wheel's suspension from the front. Lower the car? Raise one side of the parallelogram, but it's still a parallelogram. Move one corner of the parallelogram without moving the other three, then you no longer have a parallellogram. Now you need a bumpsteer kit to move the odd corner back into place.

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