I'd like to solder several flex wires (not solid wires) of a cable (max. 18 VDC) to a PCB. Now I've got corresponding THT holes (⌀ 0.8 mm), but the wire is thicker (⌀ 1.1 mm). What makes my issue more complicated, is that the board is to be part of an automotive electronics solution, which must withstand slight shocks. See the picture below:

So, what is a good method to solder these wires durably to the PCB?