From the Tire Rack site:
"Special Trailer (ST) Tire Speed Ratings
Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However industry standards also stipulate, if tires with the ST designation are used at speeds between 66 and 75 mph (106 and 121 km/h), it is necessary to increase their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).
The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity."
Tire Tech Information - Trailer Tires vs. Passenger Vehicle Tires
Personally, I'm going to be doing a LOT of further research before I starting adding the pressures described above to my ST tires. If you decide to over-pressure your own ST tires, you do so at your own risk.
Just wanted to post this TRack info, as food for thought.
Rgds, D.
"Special Trailer (ST) Tire Speed Ratings
Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However industry standards also stipulate, if tires with the ST designation are used at speeds between 66 and 75 mph (106 and 121 km/h), it is necessary to increase their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).
The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity."
Tire Tech Information - Trailer Tires vs. Passenger Vehicle Tires
Personally, I'm going to be doing a LOT of further research before I starting adding the pressures described above to my ST tires. If you decide to over-pressure your own ST tires, you do so at your own risk.
Just wanted to post this TRack info, as food for thought.
Rgds, D.
