First, 4.80-12 tires are restricted to 65 mph.
Second, 4.80-12 tires come in different load ranges: Load Range B - 785# at 60 psi, and LR C - 990# at 90 psi.
I'm going to guess the OP has LR B - and if that is so, then towing with 1500# is really marginal on load carrying capacity.
Also, there is a less than well known provision in the tire load tables that if you want to boost the max speed of trailer tires from 65 mph to 75 mph, add 10 psi. If you want to get to 85nph, also reduce the max load by 10%.
So the OP's original question? Like others, I would be more concerned about the tires than the bearings.