On my way home from work today I filled up the car with gas and as I do once a month I checked my tire pressure. I put brand new Bridgestone Potenza RE-01R 225/45 R17's on the car less then a month ago (many thanks to Jim at Tire Rack). As I checked the tires they were all high, now I had just driven from work and its about 28 miles on the express way, I work out in the country and live downtown too so there is never anyone going my way and I can drive at 75 no problem. Its Florida so the temp here is about 75*. My question is how do I acuratly fill the tires at a higher temp, is there a formula to follow as to not over inflate. Normaly I do this on a Saturday morning and I might just wait but I am curious, thanks in advance guys!

I may be a track guy, so we may use a different verbage, but I was under the impression that hot/cold tire pressure checking is really more focused on the temperature of the tire when well above ambient temps.

the fluctuation between morning and day temps is less then if you check you tire pressure after spirited driving or track/autocross use.

your psi difference from morning to day is negligable, and if you want to be more precise then either average them out or pick which ever condition you drive in the most.

Tire and car manufacturers usually recommend you adjust the tire pressure to their published numbers when the car has been driven a mile or less. The reasoning I believe is because the tires will warm up quickly after that and then there is no formula to deduce what inflation pressure should be used (unless I assume you can measure the temp inside the tire which is practically impossible for the average person).
As for the outside temp affecting the pressure, I don't usually consider that when inflating tires unless I expect wild fluctuations in temp, because most of the time I am driving at a comparable temp to when I inflate the tires. Typically you expect a 1psi drop/increase for every 10F.
I'd say your best bet it to adjust the pressure before you leave home in the morning or at the closest gas station or maybe similarly after you leave work. If you check your pressure regularly, then IMO you don't have to worry about temp fluctuations.
If you are tracking, it is a whole different ballgame and I don't have expertise to comment on that.

P.S. If your only option is to inflate the tire after having driven the car for some distance, they I'd say overinflate by a couple of psi then check the pressure the next day in the morning and adjust later on that day accordingly. A couple of trial and error tries should yield the proper cold pressure.

Tire pressure increases quickly in the sunlight. I pulled my track tires out of my trunk in the cool morning and set two of them in the sun and in 30-45 minutes the ones in the sun were about 5 psi higher, IIRC.

I am not worried about the temperature in the day but the temp after being driven on for a while. I seem to remember some kind of a table for calculating the proper tire pressure after travel of so many miles and at certain speeds. Oh well I will just check it on Saturday morning like I usually do.

I am not worried about the temperature in the day but the temp after being driven on for a while. I seem to remember some kind of a table for calculating the proper tire pressure after travel of so many miles and at certain speeds. Oh well I will just check it on Saturday morning like I usually do.
I'd say IMO there way too many other variables for such a formula to be trustable if it existed. I agree, stick with the safest way you do.

I say no way you can calculate tire pressure increase with miles driven. Way too many other variables.

LOL, I guess thats what mryakan said too... read it just before I hit send.

I say no way you can calculate tire pressure increase with miles driven. Way too many other variables.

LOL, I guess thats what mryakan said too... read it just before I hit send.
Great minds think alike, or so I'm told ;).