Neither above comment addresses the previous identified rear axle bump steer.
Thrust angle is an alignment problem. Rear toe on a straight axle is a bent axle. Both problems are not bump related.
Rear bump steer on OEM leaf spring setups is an intentional or acceptable chassis design compromise solution, and only corrected if unneeded or undesired by modifying the suspension, and not changed by simple alignment changes.
Disagree. Total toe on a straight axle can be correct AND individual toe can be incorrect. Yes, this phenomenon is usually called thrust angle but it comes down to incorrect rear toe angles.
We agree, that is why it's called thrust angle, and if that toe you note is symmetrically opposite on a straight axle, the axle itself is usually considered straight, and it's corrected by improving the alignment of the entire axle or thrust angle, and not by reducing the toe of each wheel individually.
There is almost no consideration or concern nor downside to a I suspect rather rarely found slightly bent straight axle has that exact opposite toe angles.
Note, that begs the question, do alignment machines measure each sides wheelbase, to ascertain if rear axle toe measurements are exactly opposite, giving zero thrust or do they just measure angles of toe on rear axle ?
