I'm new to fixed gear and bikes as well. I recently bought a 6KU Fixed gear with a flip-flop hub and recently while lubing my chain I heard a noise. At first I thought it was the chain but that is quiet now but when I put my ear up near the fixed cog/ hub bearings, it sounds likes a noisy rubbing noise. It's not an outrageously loud noise but as I mentioned I'm new to bikes and don't know anything. I can hear the bearings rolling and it doesn't sound like anything is rattling or out of place from what I can hear. So, I'm not sure if like skateboard bearings, they just need time to fully break in and the noise I'm hearing is just bearings that haven't been fully broken in yet or what? I currently don't have any money to take it to a LBS but I'm hoping it's a new bike/bearing kind of thing as I mentioned before, it's literally a brand new bike that I've only rode 5 times since I got it and I've only rode 3-5 miles each ride on it. I've also took the chain off and spun the crank to see if maybe it was even the BB making noise or rocking but it's as silent as can be. Everything I believe is greased up because when I first got it there was a reddish/pink grease on the ends of the bottom bracket and the rear hub bearings sound like they're greased up too. Any help would be greatly appreciated.