When you order a trailer, most manufactures will offer axle and wheel upgrades at fairly nominal prices. Not only will your load capacity increase, but you will usually get larger brakes and wheel diameters. This will give you access to many more heavy duty tires of many brands, than the 15" they repalce.

Brake drum assembllies with different stud numbers and spacing are available to replace the OEM units. This will allow you to use different wheels. Because the bearing sizes have to remain the same, the axle capacities will not increase. But because better replacement tires can be fitted, you can usually reduce blow outs and rapid tire wear.