Installed replacement tires on front. Now tires slide on axle

I just replaced my original cub cadet riding mower front wheels with aftermarket ones I found on Amazon. They are the same size and I used all the washers and cotter pins holding the old ones on but now the tires move along the steering arm as you turn causing them to rub. How do I fix or do I need different tires. I had a hard time nailing down which tires to get.