You may want to check Tire wear on the inside of tires. If you find wear then you want to check your axels to se if they have a Crown to them. If there is no crown then you must get the axels replaced (DON'T HAVE THEM HEAT BENT) If the axels have a crown then check alignment, from wheel centers on both sides of trailor. The bent axels give you camber, If you don't have camber the weight of the trailor in riding on the inside of the tires. One othe thing you may want to check, " leaf spring hangers" the hangers that hang down from the axel frame ( the chanel hangin from the main frame) Thes hangers can be bent or even have the welds broken, this will caus tire not to track stright and will show wear and caus the rig to be unstable. Next check the belly pan covers(the metal that covers the underside of the trailor) see how many screws hav fall'en out?
All of the above things have happened to our 04- 29' Cardinal 5th wheel trailor. Oh yes I almost for got we had to replace the Kenda tires (5) they were seperating.