I finally took the time to install a bump steer kit and extended ball joints on my 06 Mustang GT.
I thought it would be interesting to check the bump steer first stock, then with the extended ball joints and bump steer kit just thrown on there like most people do, then with the tie rods set parallel to the control arms like many suggest and then done up right with a proper bump steer gauge.
I'm making a how to video with all the information but the short answer is this:
1) Stock is actually pretty damn good for a production car.
2) Ball joints and bump kit thrown on-no gauge is beyond terrible. Don't be that guy.
3) Tie rods set parallel to the control arms is also terrible, but much better than not trying at all.
4) Setting it properly: Priceless.
Check it out:
Bump kit thrown on, no gauge used:
Bump steer set with a proper bump steer gauge:
Now you know the truth....you're welcome.