Calculating pressure change with temperature?

[ISX]

How do I determine pressure in psi, if I know the temperature. Like I aired my tires up to 80psi at 80F, how would I calculate what the pressure in my tires would be at 90F?

 

[russ_watters]

With a constant volume: P1/T1=P2/T2. T is absolute temperature, so 80F is actually 80+460=540 R (Rankine scale).