I'm confused...your truck has a GVW of 8600 KG (almost 19,000 pounds) and you say it can only haul 3,800 pounds, that tells me your truck weighs 15,200 pounds empty. Is that right?
Here in the US the tire rating needs to meet or exceed the axle rating so the axle rating can be used to calculate your max load. In your case the front tires need to be rated at 2250 pounds each (4500# axle) and the rear tires need to be rated at 3750 pounds each (15000# axle) to be legal to max out at 19,000 pounds GVW. If you use a lower rated tire then the GVW gets lowered as well.
Mike B
