The ZPU-2 must be a substantial weight for (after all) a civilian car. The gun itself weights more that 600 kg. Add the platform, ammo, the crew and other equipment and the load will easily reach a tonne. I decided to give the tyres a little sag to enhance this overload effect.
For that I used an ancient Chinese technique – basically you need to insert a screw that will flatten the tyre slightly. I’ll show you how to do it step by step on another occasion. Still, the method is widely known- if you’re impatient look it up elsewhere.