To set or change the bumpsteer you have to shim or somehow move the tie rods. Unless the new parts just measured out a better bumpsteer than before. Which is cool.

If anyone is more interested in the details of bump steering a car read here:

Making Bump Steer Corrections: http://www.longacreracing.com/articles/art.asp?ARTID=13#Q3

BTW these Longacre tech articles are pretty darn good :

http://www.longacreracing.com/articles/index.asp