Hey guys, been watching my front tire (knobby) and it looks like the center tread is wearing away. If you're looking at the bike from head on, the center tread is wearing at a slope, from "north" to "south". I'm talking almost 3/8 of an inch all the way to almost nothing. I bought the bike used, 2 1/2 yrs ago and I would imagine the tires are the originals. Is that just old tires wearing really bad or what? I think I have 20 psi in the tire and I do 99% street riding. Back tire is fine, looks like I'm gonna have to get a new front (may go street style tire). Just wondering what is causing the front to wear so strangley. Thanks for any info fellas...