Question: how fast can you drive towing a travel trailer?
Answer: Drive no faster than your tow vehicle's economical sweet spot. (From what I've read, sweet spots typically are in the range of 55-65 MPH.) According to Roger Marble (a.k.a. tireman9 on RV forums), it's best to tow no more than 60 MPH when using ST tires and some manufacturers recommend not towing faster than 60 MPH.