38.5X14.5R18 tires are 38.5" tall, have a section width of 14.5", and fit wheels with a diameter of 18. The circumference is 120.9" that translates ...
35X13R18 tires are 35.0" tall, have a section width of 13.0", and fit wheels with a diameter of 18. The circumference is 109.9" that translates into ...