Just to throw a further wrench in the works:
Tire Rack has taken the Goodyear Bulletin posted at its site one step further, and rolled it into an info page regarding ALL ST tires. The language seems to me quite a bit clearer than the Goodyear bulletin. I guess the one thing that would be a topic of controversy per this page is how "reliable" a source it's considered to be.
Here quoting from
Tire Rack Tire Rack wrote:
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.