in my experience the rattle is usually from the fittings inside the bus, not the bus itself - mounting brackets for information screens or advertising panels, s

in my experience the rattle is usually from the fittings inside the bus, not the bus itself - mounting brackets for information screens or advertising panels, seatbelts on the accessible seating, that sort of thing. and part of the rattle is just down to under-use - a bus with all the seats filled shakes less, because the suspension is tuned for a full bus not an empty one. one of the buses i ride frequently has a ski rack installed in it that looks like a homemade contraption, and it rattles like crazy.