whenever i take my feet off, the cranks keep rotating and this prvents me from doing no-footers and stuff. it feels like the thing that allows me to pedal backwards (drawing a blank on what thats called right now) it feels like it is too tight like if i were to pedal backwards, the whole bike would go backwards. i've tried loosening the chain, and tightening the chain, but that doesnt work. what should i do. please help me. thanx