C5 Corvette concentric

[VenturaII]

How can the lower control arm concentric be used without causing bump steer?

[astroracer]

There isn't enough movement of the inner control arm point to affect it dramatically. The suspension is designed at nominal with the D bolt and washer straight up. There is only about a 1/4 of an inch of travel either side of nominal so that little bit of movement will not alter the pivot point enough to be noticable.
The problem with bumpsteer is raised when trying to install a R & P steering system on a suspension that wasn't designed to use a rack in the first place, like the early A, F and X bodies everyone is trying to convert. Simply bolting on "any old rack" will never work. The inner pivot points of the rack AND the install height have to be correct to work efficiently with the old suspension geometry and getting these correct is very difficult without doing a lot of calculations and "moving" of current components to make room for the rack.
What you need to know about the C5 suspension is that it was DESIGNED to use a R & P steering system. That is big factor. A little adjustment will not effect the overall design and is actually necessary to overcome build tolerances incurred during manufacture.
Mark

[VenturaII]

Thanks for the answer Astroracer.