315.70 tyres not rated at 7.5t

ROADRANGER:
I have recently had to replace a pair of perfectly good tyres for test as I was told they would fail due to them only being rated at 7.1t
When the axle weight is 7.5t.
Who knew?

Also If on aluminium wheels check the weight rating some are 3.5 tonne some are 4 tonne ,can soon catch you out when front to backing wheels round .