One tire on my triaxle showing sidewall cracking. Other tires seem OK. I just purchased the trailer/boat combo new. The trailer is a 2007, the boat a 2008, so they have been sitting for probably a year or two. Should I get this looked at?

That will happen when it's parked in the grass for a while & out in the sun. Replace the tire. That's not good.

I can see the future thru those cracks,I see tread coming off killing fender soon.

It is likely under warranty

Even if it is under warranty, I'm leary of the Carlisle tires. Haven't heard many good things about them around towing forums.

Also, most local tire shops recommend upgrading to E rated tires for my load, about 12.5K lbs, for extra safety margin. IIRC, E tires need 80psi to achieve rated capacity. The stock Carlisle wheels (15x6, 6 bolts) on my trailer are rated to 65psi. So an E upgrade would involve a wheel upgrade as well, roughly doubling the cost. What think ye boat haulers?...should I replace with D rated or do the upgrade?

Tire covers are your friend if the trailer spends time outside in the sunlight..

Upgrade to the E's, cheap insurance, relax while towing.

Definitely...already picked some up at local RV supply.

I'm leaning that way.

That tire is MORE than a few years old !!

tire life doesn't begin during the first drive. Tire life begins the day the tire pops out of the mold. the rubber is cont. drying out. every tire will have a date (in some form of cryptic code) stamped on the side of it. the MFG. generally consider tire life to end 3 years from date of mfg, 0 miles or 100,000 miles. ALWAYS get the code info for tires you want to purchase and check them. they may be shiny and look new, but they could also have been baking and drying out in a warehouse for 3-5 or more years.