Best place to position a jack
The locaiton I use is very near the end of the axle, there is a plate running vertically that the axle will pass through before the torsion part of the axle. I use my floor jack and position it where the edge of the axle and this plate rest on the jack face. If you go in at an angle with the jack it works well. Always have jack stands ready to place for saftey. Also if you are just changing one tire I recommend the Trailer Aid. it works well.
I just replaced all 4 of my tires and never moved the trailer. Took two off and went to Discount tire, they mounted the new ones, took them home placed on one side then moved to the other and removed them worked out well. whole process took about 3 hours.
2011 Flagstaff V-Lite 30WFKSS
2014 F-350 Super Duty Lariat 6.2