Comment: Using the <span class="highlight">4psi</span> Tyre Inflation Rule

The gas law you should be using here is Boyles. Any calculations done would unlikely be accurate as you need to have a constant volume to work with which a tyre isnt. As a tyre heats up it will stretch therefore increasing the volume thus decreasing the pressure how much is hard to say but it it likely that the actual pressure change is going to be minimal