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I got bored and did a 3D model to explain what words have great difficulty to express.
This comes up so often it needs to be explained properly. Steering arms are meant to act on the same plane as the steering rack.
The further you are from the plane of the steering rack, the more bump steer you get as the steering arm moves in and out as the strut compresses and rebounds because the pin for the tie rod is not perpendicular with the rack.
Don't try and look at the whole thing, just watch the link pin for the tie rod end.
Not 100% to scale, but it clearly shows what's going on.
Corolla Strut Not too bad in a lowered position, but the steering arm is not on the same plane as the steering rack.
RA40 Strut Fitted to corolla with longer LCA's and/or camber tops ... Steering arm is not acting on the same plane at all.
Now lets have a look with some Roll center adjusters added:
COROLLA RCA Notice that the steering arm now nearly operates on the same plane as the steering rack
RA40 RCA There is an improvement of the angle, but it still isn't as good as a factory strut.
To some people this kinda thing won't worry you, but it's all about how hard you drive your car, or if you're planning to race competitively. Things like this to the eye don't look like much, but when it comes to shaving a few seconds a lap on the track to mow down a racer with more power it can mean all the difference
The steering arm references aren't spot on, but I hope you can visualise what I mean
