8 inch hub bearings that get hot, are the result of improper cleaning and packing with a good bearing grease.
I pulled my tag-along 4500 miles in a 30 day period and a lot of it at 75-80 mph.
I carry an IR Temp gun and shoot the hub temps just as I come to a stop.
The 8" wheels usually are about 150°
The front wheel hub on the bike is ~125°
The rear hub is about 134°
a new Harley Classic pulled to a fuel stop with me once.
I took temperature readings on his front and rear wheels.
there was not 5° difference between his bike, and my bike.
So, those little 8" wheel running about 15° hotter than the bike's front wheel?
I doubt they will ever give any problem....
it is not the size of the wheels, it is poor maintenance.