These things have no suspension to speak of, rather like a modern buldozer or 360 excavator. The suspension on these is in the seating and the lack of flex in the running gear is to keep the damn thing still whilst it does it's job (moving earth). In the LRMBT and Chimera this would compensate for a lack of hi-tech gun levelling mechanism. It'd still be rubbish, but it wouldn't be able to bounce on its springs when it fired its battle cannon.
Woe betide the Iggy AFV crew, whose attrition rate is going to be related as much to muscular-skeletal disorders as it is to enemy action.