Tires flex as we drive and as they flex they generate internal heat. The faster we drive the more they flex and the hotter they get. They are designed to work best within a specific range of internal heat. Too cold, they don’t flex enough, too hot, they begin to fail.
When operating near or at the maximum load rating of your tires it is important to stay below the maximum speed rating since very a high internal temperature decreases the maximum carrying capacity as much as 10%. Operating at maximum speed and carrying capacity may also require a greater inflation pressure.
To stay safe and get the expected life from your tires you need to watch your speed, tire pressure and cargo weight and stay within their design limits.