[topat46]

Does anyone know the size of this pin/rod?

 

[Mark_]

Does anyone know the size of this pin/rod?

Is that the one that comes with the OEM jack ? If so, it screws into one of the lug holes, right ?

If you don't want to get an OEM one (recycler maybe ?), then the threaded part has to be M12x1.25
Maybe look for a long M12x1.25 carriage bolt and simply cut the head off. Or buy a long M12x1.25 bolt, cut the head off and cover the thread on the guiding part with strong tape (Gorilla) so it doesn't hurt the wheel as you slide it on.