Never heard of tyres being under the load rating.
Its normally rims that are under the load rating. What car did you get the defect in if you dont mind me asking?
And what the load rating is refering to is the amount of weight each rim can with stand. If its less then what the car can carry full load ( i think ) then the wheels arent strong enough, and when the wheels are under stress, not a good idea driving around on them...
Mod.