Whether you have a knobby or street tread on a tire will make no difference to the internal pressure. The TFT will show a compensated pressure @ 20 c but even a really hot tire should not have 10 psi difference. Confirm that the gauge you are using at the tire valve is accurate and then compare them when you know the tire is at 20 c. It is also possible the sensor was damaged during the tire change. Also try totally deflating then reinflate and check again.