It is very easy to confuse speed limits set on highways by Federal, State and or Municipal Authorities with the maximum speed you can travel with ST trailer tires. A speed limit set on an interstate of 65 mph will be due to highway conditions including traffic density and highway design. Under better conditions, this does not mean that you cannot travel safely at a higher speed (although illegal) of 70, 75, 80 or even more with your car alone. Most cars are more than capable of doing that providing it is in good mechanical shape. However, ST trailer tires typically have a maximum Speed limit of 65 mph. This is due to the type of tire construction that is used. The rims made for these ST tires may also have a maximum speed limit as well. Can you travel at 70 or 75 mph? Possibly. I have for short periods at one time or another. Should you do it continually? Well, the maximum limit of 65 mph is not set by Federal, State or Municipal authorities, but by the tire manufacturers. You decide, I dont purport to be smarter than the engineers who designed the ST Trailer Tires and will attempt to keep traveling with my ST Trailer tires close to the 65 mph maximum speed as possible. Here is a link to Carlisle Tires whose recommended limit for ST trailer tires is 60 mph. [smg id=4654 type=av] This if for the 99% of us who have ST tires on their pups or HTT's and is not to include those that do not have ST Tires such as some off-road pups and some Aliners. Also, Goodyear has some tires rated for 75 mph, but they are coach/bus tires, not pups or TT's or HTT's.