Switching from 15 to 16 inch tires

I'm upgrading my triple axle ww to 16 as well, mine was rated for d rated tires though. the perfect fit from 15's are lt225/75/16 E tires, they are only barely an inch taller, the capacity is slightly less by about 150 lbs per tire BUT it is a much better tire than an st tire, in my case even though I have E tires my trailer came with D tires so I will be slightly more than D rating. The LT's will still be able to handle 10,720 lbs, if you get michelin xps tires or bridgstone durvais you will have absolutely no problems. On the cheap the falken wildpeak HT or sumitomo encounter ht are very heavy duty and long wearing. LT and vehicle tires tend to be slightly under rated to give them a bit of margin of saftey when overloaded, where as st tires don't have to conform to those standards.