According to GB 1589-2016 regulations on axle loads and vehicle dimensions, what is the primary risk of loading cargo too far toward the rear of a heavy truck cargo bed?

1. It reduces downforce on the front steering axle, leading to degraded steering control and headlight upward mispointing
2. It causes immediate pneumatic failure of the service brake dual-circuit diaphragm
3. It locks the transmission inter-axle differential into permanent 4-wheel engagement
4. It increases front tire temperature and accelerates front tread wear