Tyres especially large tyres build up heat internally, because of the way they are made. there is a natural heat build up in the tyre wall because of movement of the cords and carcase materials within the rubber compound as the tyre rotates and flexes. That is why older tyres with more layers of cords run hotter than more modern constructed tyres. Cross ply, bias belted and radial construction are made for different but overlapping purposes. Steer tyres heat up for several reasons, running at the wrong pressure, overloaded, exceeding the tonne mile per hour rating of the tyre, or running out of track. Older crossply tyes that have been standing in one spot for a some time settle to that shape and need to warm up to become round again usually giving a rough ride for a few miles. Old mechanics storing vehicles for the winter always put them up on blocks.