On my Chevy Volt, which has built in tire pressure sensors (215/55R17 tires) the recommended tire pressure is 38 psi. However, that’s supposed to be the inflated pressure when cold (presumably the coldest temperature of the day, which can vary between seasons). When driving, as little as 5 minutes of driving, the PSI will go up by 3-5 psi. 

Should you set your tire pressures when hot (aka after having driven on them for a while) , you are almost certainly under inflating the tires. Dealer did this to me, and I failed to check the tire pressure before substantial wear (due to under inflation) had occurred. My bad for not paying attention. 

> On Oct 19, 2015, at 7:15 PM, Dave Mcneely <mcneely4@COX.NET> wrote:
> 
> Dan, I'm not sure what you mean.  From what you wrote, it could mean putting an additional 3 psi into the tires if they are hot.  ????  Or it could mean reading the gauge, and concluding that the tires have 3 psi pressure more than the gauge reading.  ????   Do you mean to say either of those things?  Neither makes sense to me.  Or perhaps you mean to say that the gauge reading of the tire, when hot, is 3 psi higher than it would be at ambient temperature.  But wouldn't that depend on the two temperatures relative to each other?  That might vary considerably.
> 
> I make it a rule to check the tires when the vehicle has been parked for several hours, preferably in shade, and to inflate them to the recommended pressure for the vehicle at that time.
> 
> mcneely
> 
> ---- Dan N <dn92610@GMAIL.COM> wrote:
>> regarding change in PSi and temperature...
>> 
>> the manual of my SUV recommend adding 3psi if I check my tires are hot
>> (after driving on highway)... not scientific but just reference from user's
>> manual...
> 
> --
> David McNeely