My son's bike is locked with a U lock for the rear wheel and frame, that he carries, and a heavy chain for the front wheel and frame, that he leaves on the school rack (left it there all summer, I learned). Bike has Allen heads filled with silicone caulk, zip ties securing the lights. A high theft zone but so far, he's been okay. About half of the bikes are locked with just cables so his is the hardest target on the track.