When checking tires, which of the following should not cause concern?

When checking the tires as part of a pre-trip inspection, make sure the tires have sufficient tread. There should be at least 4/32 of an inch of tread in every major groove of the front tires, and at least 2/32 of an inch of tread depth on the other tires. Tires should not be mismatched in size and radial and bias-ply tires should not be used together.