I am new to the while dirt bike thing so excuse my ignorance. I have a Dunlop 120/90-19. I am looking for a rear tire. I'm not into the motocross racing at this time. I need a tire for trail ridding. I'm wanting to keep the price low. Anyway I'm looking at the artrax sr 1 or artrax sr 3. Also when I was on motosport.com it is saying that my bike 2001 yz125 tire size is 100/90-19 what is the difference?