I am tuning my bike up because I am taking it to college with me. I have ran into a problem however. After doing some research I am still confused. What happens is I loosen the bolt that holds the cable into the derailleur and I turn my gear shifter so that it is in the smallest gear. Then I go ahead and I tighten the cable and screw it back on. Everything is nice and tight at this point. Then I lift the rear wheel up to pedal and switch gears. Immediately after switching gears I get a lot of play in my cable and it will not shift to the larger gears. Any explanation/help would be much appreciated.