You could also try switching which set of outlets your tire warmer is connected to. The 220v outlet uses both legs on the generator, since the trailer is only 110v it will only draw from one, I believe the 2 20a plugs are on opposite legs. So if the trailer is drawing from leg one plug the tire...
What amperage is your trailer? If it uses a 15/20amp plug (standard house) then you should be fine plugging in to the 110 outlet. Your trailer will have a breaker that won't let you exceed that amperage anyways.
For 30amp I bought...
I have placed my order through Folsom. I am still waiting on my 2nd order. I screwed up on the 1st order. So far they have been great to deal with. I even took my mother in law in to the same sales guy (Anthony) to get her F250.
As Daemonic3 pointed out no 2 experiences are the same.