A bushing should be selected so that the kingpin nut just engages the nylon locking point. Over tightening this nut prevents the truck from moving properly. If the truck is too loose, get a harder bushing set.
Most stock skate bushings are an afterthought. Designed to be cheap and get the basic job done. FAT ANT Bushings have gone to the next level and are offering high quality bushings made of select high rebound urethane.