Probably best put here rather than the new rider forum, since this is a more technical question. So I started up the bike the other day at work, and as I started riding the friction zone out of the speed zone that is the work parking lot, I heard what I can only describe as a rubbing noise coming from the rear wheel. It's a rhythmic noise, so clearly rotational and not static. I only notice it at low speed. I may not have otherwise noticed it, but it was loud enough to catch my attention even over the Nightstick pipe with end caps removed. Now to be honest, part of me isn't that concerned that it's something serious because I haven't noticed anything wrong with the handling of the bike, but rubbing noises are generally a bad thing, I just don't know what it could be nothing appears visibly wrong with it. Any ideas?