Bump steer most commonly occurs when the axle is inadequately located/attached to the chassis.
So, one front wheel hits a bump. It drives that side of the axle back causing it to steer in that direction.
Particularly common on Safari coaches with Torsilastic suspension, as there is only ONE forward link (driver's side). So, if right wheel hits a bump that side of the axle is driven rearward, which IS a steering input. Easy fix is to add a forward link on the right side. Created quite a cottage industry for Ralph Andrews/Pioneer Metals in WA state.
