i am new to cycling and need a faster bike other than my MTB. someone just gave me a centurion road bike all the gears work just fine cranks ect.... just the tires and tubes are rotted out and need replacing. it seems to be a higher end centurion it has all shimano componets but the cranks are the 400lx series not the 600lx. basically what im getting at should i spend the 600$ get me a very low level modern road bike or should i just slap some tires on this centurion and be done with it? please help