Were we not paying attention in O Level physics, Paul?
Boyle's Law, P.V/T = Constant. As temperature drops, so does pressure in a constrained vessel (ie constant volume).
It's the combined gas law not Boyle's Law that you are referring to. A 20C temperature drop would only reduce his tyre pressures by 1.5 psi but likely the pressure guage isnt wildly accurate anyway
