15 inch tires on 14 inch axle

Anyone have experience or opinion on the consequences of putting 15 in wheels on a USED 2720 TM? I realize this would not increase the GVWR but the tires would be much less stressed. I have read the stories of tire failures but have not seen any axle failures. I plan on some really long distance hauls over the next couple of years. There is a site offering a packaged wheel and tire as follows:
Tire: ST225-75-R15BD Load Range D Load Capacity: 2540 lbs. at 65 psi. Bolt Pattern: 5 on 4-1/2. This tire is about 1.6 in larger in diameter and 0.3 in wider than the ST215/75R14. I also plan to add the 2.5 inch lift.