[seanflyon]

I don't imagine any sort of suspension would be needed. The system is always loaded (with only a slight increase when the vehicle is over a given support because the tube is most of the weight). It needs bearings, but they don't have to move quickly or be particularly low friction. Even if the bearings failed the tube would just slide; you would want to replace them before too much wear, but it would not be urgent.

If that is too complicated, just put in replaceable slide plates. More regular maintenance, but fewer moving parts.