SAFETY NOTE: While towing, hand check the temperature of wheel hubs at every stop. I always do a walk-around to check tires, hubs, lugnuts, and hitch.
You got it out before me.I do that very same thing when traveling, I use the back of my hand to feel for heat..
A new toy I bought since this incident is an infrared temp reader. Less than $30 and I know the temp of the bearings, tires, the guy driving beside me, oil pan, roasted marshmello, a tree...............fun at parties to
As far as the back-of-the-hand check or thermometer check goes, how hot is too hot? My old Jayco with the 12 inch wheels got pretty toasty at times.
With my gun on it 37-39C\100F measured at 25C\77F ambient. If you can't hold onto it with your hand it's too hot!!!! It will also depend on the outside ambient temp. Again though if you can't hold your hand on it it's time to check it now!