My heavy 6x12 flatbed trailer has 8 inch wheels with load range D tires rated for 1075 pounds each. I've towed this trailer loaded with 2 ATVs for up to 250 miles at a stretch with no issues. The tires and hubs do not get too hot to touch. I debate if I should go to a 12 inch wheel with a load range C tire instead. The reason would be to have a larger tire for less rotations per minute and less heat build up. Is a larger wheel and tire advisable or are the 8 inch wheels okay? Loaded weight of the trailer is 1700 pounds.

 

If you're not having issues with the 8" tires I wouldn't bother changing them until your tread wears out. Kind of, leave well enough alone type idea. Just my own .02 worth. If you're worried about it the peace of mind might be worth changing them.

 

New 8" will do fine but 12" are better. The only thing is what is your new clearance above the 12" tire with two ATVs plus when you hit bumps will the tire now rub the trailer bottom Now?

If you stuck on 8" wheels you can buy high end wheel bearing for peace of mind. Such as SKF or F.A.G .

I bought a Trailer and the bearing on one side failed ,turned out it came with some China junk bearings so I replaced both side with some brand (Forget which brand) made in Germany ,it sure is a pice of mind on those long trips.

Just bring you old bearings in a bearing shop and they will measure them and tell them you do not want junk.

 

Since load and bearing temp aren't issues, the only other advantage might be in the speed ratings but if even that's not an issue for you, I would stick with 8" as well.

 

Clearance would be my only issue. On my 4x7 trailer I upgraded from 4.80 to 5.10, just an inch difference in height. Also had my bearings repacked (been 3 years). Just depends on if you think it's worth doing. Also consider (if you haven't already) getting a third tire/rim for spare.

 

I have always stepped up tire sizes where possible. As you said less rotations easier on both tire and bearings. You could always toss the 2 8" tires on the trailer for spares. you would have to change 2 if you got a flat but ya already have em

 

Looks like good tread left on your 8" you could sell them, that's what I did with my smaller ones I took off (sold for just over half of what the bigger ones cost). You don't think someone would want used trailer tires that size but there is always someone who does.