Manufacturer has a chart for what pressure to run at what axle weight and speed. It shows 55mph for the uneducated to avoid problems. At 60-70 mph the front axle was at 70psi and the rear at 85psi per the chart. 40k miles or more easy. At 70 they are louder than at 60mph for sure. Lots of sound deadening material so still easy to carry on a conversation and listen to the radio without having to raise your voice.