I have recently purchased a 2009 Cub Cadet LTX 1045 hydrostat. The rear tires are 20x8x8 but they are different brands. One is more flat across the tread and the other is more rounded. Will this hurt the rear differential? Should I get two matching tires? It has 440 hours on it. Is this a lot for a Cub Cadet. Thanks in advance.