Your speed is your responsibility. If your rig is not violating any safety features I see no reason for not traveling at the allowed maximum speed of the state you're traveling in. However, you should insure that your trailer tires have a speed letter or other speed restriction identification on the tire sidewalls that will allow them to safely travel above 65 MPH. Almost all of them have some form of speed limiter on their sidewalls. In the speed lettering system "L" is for 75 MPH. The only current trailer tire manufacturer that I know of without a letter "L" or higher is Maxxis.
That's for radial tires. Bias ply may be 65 MPH or less. Carlisle letters bias ply with a "J", 62 MPH.
RVIA no longer recommends bias ply tires for any trailer fitments above 13" OD.
