#3 Rebuilding a 1963 Cub Cadet Garden Tractor (Part 2 - Front Tires Stuck on Rim) 

You could wire wheel them down first and see if that removes the majority of the rust crud. Then is you have a media blaster, you could use that to give a better finish. Then the typical primer and top coat of paint and I am sure they would work again. May not be the best looking, but would do the job all the same...

Those are rough. Get yourself a plastic tote and soak them in a water vinegar solution for about a week and that rust will be nothing but a memory.