I think I may have found my issue, but I can’t explain how or when it happened. In the migrated blueprint the collision section of all of the RoadWheelPhysics… components had the object type in the custom collision section changed from “Wheels” in the MMT project into “Suspension” in my new project! (I do hate the way these sort of things randomly happen with this blueprint stuff). Changing them all back to “Wheels” seems to work, They are now “Query only” collisions that do “Block” on the floor slab which does make sense. I just have to hope nothing else was changed in the migration process!