How much vertical weight can the Pololu Wheel (80x10mm) item #1430 withstand? I have a rectangular platform with two of those wheels attached to two 50:1 Metal Gearmotors 37Dx54L in a front-wheel drive configuration, and two generic coaster wheels in the back of the platform.
We do not have those wheels characterized in that way, but we generally consider them appropriate for applications where they are supporting up to a few pounds. Just to give you one rough data point, one of our engineers tried to stand on the rim of one while it was upright and it did not break. I suspect that the shaft of the motor would be more likely to reach its limit before the wheel (assuming you have the wheel mounted directly to the shaft).