I towed a F 150 behind an Allegro Bus for 35000 miles the last few years and never smelled anything like this. My wife stopped at a store after we had towed and two men were admiring Bronco and walked up to it and where very concerned that something was getting very hot even concerned it might...
I have been flat towing a F150 for 15 years and I can tell you it is not rubber dust. We never had this smell when towing F150. Something is getting hot after flat towing.