3312.5-R18 tires are 1.79 inches (45.4 mm) smaller in diameter than 305/70-R18 tires and the speedometer difference is 5.2%. 35X125R20 tires are 35.0″ tall, have a section width of 12.5″, and fit wheels with a diameter of 20. The circumference is 109.9″ that translates into 577 revolutions per 9l4s0g.

35 12.5 r18 in metric