If you are going to ride it on the street get the Dunlp[ CD-8 (hard compond) they should wear pretty good on the street since its hard to wear them out on a groove track spinning like crazy. If your going to race it get the Maxxis CD-3 (soft compound) you'll like them on the track. 19" is the standard dirt tire so I dont know if anyone makes them 18" or not. Mitas also makes a really nice compound race tire. The Maxxis and Shinko have the same tread pattern with the Mitas being similar to them, the Dunlops are totally different pattern from the other 3. I dont think any of them are DOT legal.