So not mentioning brands here since I buy from several marine warehouses but talking about any 12in bias tire the max speed rating is 60mph. Most bias tires sold on the cheap, I don't care which brand, go to their website and read ratings. Almost all are not intended for Interstate use. I was going through a pair a year just running around here. I was even buying a pallet of trailer tires each time the "Road Show" tire deals came around (always sold out). After noticing how quickly the tires wore I read up on the Duty or Service rating. Most said not recommended for sustained highway use or something to that effect. I just bought 3;
Carlisle Trail RH Trailer Tire - ST145R12 LRE 10PLY
$61.00 from Walmart. 75mph speed rating. They are a little taller, I had to turn the fender bolts around so the carriage head was on the inside to clear fender. Now for my personal trailer tires I go somewhere else than my suppliers to purchase.