I've never run a panhard bar and never had a bump steer problem because I always run a Ford pickup steering box with a traditional drag link that runs fore and aft. When I am steering, the forces are straight forward and backward, rather than side to side, as when using a Vega or similar cross steering box.

Everything I have ever heard is that it is manditory to run a panhard or dead perch with these cross steering boxes because of the way they shove the axle from side to side when turning the wheel.

I have also heard that radial tires accentuate the effect because the sidewalls are made to flex. Don't know if that is true, as I always run bias plys. This is one of those subjects no one seems to absolutely agree on, and there are 100 ways to go about it.

Don