Originally Posted by mihlbach
Its conventional wisdom among BMXers to run a fat tire up front and a skinnier tire in the rear. BMX races consist of short straights with jumps and a number of extremely tight banked corners, all on dirt. I've always thought that the big tire up front gives better handling and traction through the turns. I've never actually raced BMX..I was more into freestyle. At any rate, I suppose that would make sense for conditions other than dirt as well.
No, this is right for dirt but i would do the opposite for pavement. As others have said, slicks have better traction on smooth surfaces, so should be on the front for street riding. I guess you would go the other way around for riding on loose surfaces.
One other point. If you do mix tires, make sure your spare tube will fit both. For example, a 1.5 tube will fit 1.25 and 1.75, but maybe not 2.25. If your two tires are real far apart in side, you might need two spare tubes.