where to replace popup trailer tires?

A lot of people, myself included, buy the trailer tires and wheels together online, and put them on yourself. Save the old ones for winter storage. You can find name brand FRESH quality tires (I prefer Kenda tires) for cheaper than the walk-in stores. The best deal Ive found for my tire size, ST185/80D13-D, are at TrailerTiresAndWheels.com with free mount, balance, and shipping to your door. A buddy got 9 week old tires from there. I'll be shopping there before summer. Another place is etrailer.com. I do suggest you call to ask specifically what the date code is on the tires they are going to send to you to make sure. The date codes are on the tire. 4 digits representing the week and year the tire was made. 3514 would indicate that they were made in the 35th week of 2014. Replace your tires every 5 years no matter what they look like. Good Luck.