Rod flex under carriage weight

[Sebastian Finke]

??? The rods in our CTC are 8mm also but there is No flex or sag in them that I can see.

Trust me your rods will sag with force applied. 0.1mm is not discernible without using a gauge (either mechanical or light)

??? And I have put a lot pressure on them when cleaning extruders.
(at least 20 or 30 pounds of pressure).

Why would you put your printer through that? Adding 15kg to the rods will ruin it.

I'm wondering if there is a difference in Wall-thickness of those tubes ?
thicker walls would certainly make them stronger.
Also if they are really Rods and not Tubes they would bend easier also.

They are solid rods.