My long understanding is that tire pressures are meant to be set with the tires at ambient temperature - in other words, not after long and/or fast driving, which makes them warm up due to flexing. I am sure that good tire designers account for the whole range of world weather temperatures, so you should do your setting to the same numbers regardless of whether it’s winter or summer. All tires have a maximum permitted pressure molded into the sidewall, which is only to indicate to you what the tire’s strength is - it is NOT what the car requires, which may be much lower. It certainly can’t hurt to reset your pressures more than once during the year but the most important reason for that is to catch slow leaks and fix them before driving on a soft one ruins it. It’s also important to keep in mind that even tires in perfect condition will lose a few psi leaking out the valve, over one year. 365 days from now I’d expect to see your 4 tires to be at 28 front 27 rear - and if there are outliers in the numbers, look for a nail.

 

It certainly can’t hurt to reset your pressures more than once during the year

28 front 27 rear

I check our cars once a month, and during the fall maybe every couple weeks, because it goes from 30+ to -10 before it stays somewhat constant again. If the car has been sitting in the sun I postpone that check, because one side of the car will be warmer than the other. The 2007 Forester B pillar sticker said 29/28 psi, which got me "underinflated" wear patterns, so since that car and every car since I always inflate 3 psi higher. Our old Audi had a range of pressures on the B pillar sticker, which varied depending on how much weight was in the car (indicated by passenger and suitcase icons).

 

Tire pressures on the door placard say Cold Tire Pressure I believe, that's the recommended pressure. They know that when the tires are rolling they will heat up. Boyle's Law and all that. I find it best to check the pressure in the morning in the garage. Outside the sun can warm tires on one side of the car and that will increase the pressure. When they determine the pressure they choose a blend of comfort (lower pressure) and handling (higher pressure) . Myself I add 2 PSI-G to the door placard in the summer and 3 PSI-G in the winter. Just a personal preference. Might help with better MPG's but hard to say. The owners manual has some good info.

 

@davidwal

Do you re set the tire pressure when the temperature changes?

If you don't the pressure could be low in the cold winter months or high in the summer.
As was noted, all tire manufacturers state to set tire pressure when cold, as in when it's cold for that time of year.

Tire pressure will drop from 1 to 2 PSI for every 10 degrees F the temperature drops, so a 50 degree F drop when a cold snap hits can drop your perfectly set summer tire from 33 PSI to 23 PSI likely triggering a TPMS warning light.

The door jam is a guideline, and as @Peaty noted, it's a compromise between a soft ride and good handling/mileage.
It's not a magic number always ideal in all circumstances, but it's a pressure that will work for most, most of the time.

Optimal tire pressure is also related to the weight the tires are carrying, and that isn't often static.
If the car is loaded near its GVWR, it will benefit from some additional pressure compared to a car with only the weight of the driver on board.

 

Here is my simple approach. I use the Info Button on the steering wheel every few weeks to select & display the tire pressure that the TPMS displays on the dash when I start the car up and first drive it down the road before the tires get warm. If the PSI is off the 33/32 setting, I do add or remove air pressure the next morning to the correct setting (using a hand held tire pressure gauge) after the car has sat in the garage overnight. And yes, the TPMS display is the same as my hand held tire gauge reading. Since its actually printed on my Forester's tire sidewalls that the maximum allowed pressure in them is 44 PSI, I also do not get concerned when I see the TPMS display 36 or 38 PSI when driving 70 miles/hour on the interstate highway during the summer. One needs to look at their own tires as that maximum allowed pressure varies by tire size & brand.

Once I got lucky & also discovered that one tire actually had a nail leak in it because the TPMS display in that particular tire was always lower than the other 3 tires when I turned on the Info Button a couple of times.

 

I agree with the other comments on this thread. Your initial tire pressures are incorrect, though. The 2024 recommendation is 35psi (front) and 33psi (rear).

 

I am in another camp, that states that recomended cold pressure is for an Index-temperature of 20 degrC/ 68 degr F.
In my camp Porche and BMW who give on tpms screen the actual pressure, but per axle the recomended pressure for the setting, calculated from 20 degrC to the temperature in tire, also sended by the sensors.

Some motorcycle tpms give on screen the pressure calculated from temp in tire to 20 degrC.

Rimex, a mining tire company, cals it index temperature, and uses it.

Idea behind it.
Main goal of determination needed pressure is that not any part of tire-material overheats.

If now 40 degrC/ 104 degrF outside, the cooling down of tire-material is lesser, because of lesser temperature differences between tire-material and in and outside tire air.
But then by the higher pressure, lesser deflection, so heatproduction, wich compensates the lesser cooling down, so tire-material still not overheats.
So never blead down hot or cold pressure on a 40 degrC hot day.

When for instance zero degrC/ 32 degrF the other way around, so more heatproduction and more cooling down.
But hen you are allowed to highen up the pressure for riding quality and fuellsaving, tiremayerial only stays cooler then.

Easyer system, calculate back to 20 degr C , if then the needed pressure, change nothing.
Let the pressure flow with temperature-change.

So in that heated garage ( if heated to 20 degrC , do you do that?) fill to determined needed cold pressure, and at other ambiënt temperatures while driving , balance stays automatically alright.

 

In case this is helpful, I found a table on this link which notes the tire pressure setting value by ambient temperature for a range of sticker recommended pressure values.

 

I made an easyer list.
Is for if cold filled at 70 degr F and degrF change per 1 psi change.

Bur if you use it for cold filled at between 60 and 80 degrF , it wont give dramatic differences.

You only have to remember you cold filled pressure, and the degrF change/ psi .

Then on the road you can calculate by head acurate enaugh for the goal.
Even if you round to 1 degr acurate enaugh.

Also made list for bar and degrC .
And Psi and degr F and C. so if you use those, write it and I give that list here in this topic.

Then you see that the often used rule of tumb of 1 psi/10 degrF can be used for cold filled at between 36 and 40 psi.

70degrF./degrF/psi

20psi/15,5F/psi
21psi/15F/psi
22psi/14,5F/psi
23psi/14F/psi
24psi/13,5F/psi
25psi/13,5F/psi
26psi/13F/psi
27psi/12,5F/psi
28psi/12,5F/psi
29psi/12F/psi
30psi/12F/psi
31psi/11,5F/psi
32psi/11,5F/psi
33psi/11F/psi
34psi/11F/psi
35psi/10,5F/psi
36psi/10,5F/psi
37psi/10F/psi
39psi/10F/ps
40psi/9,5F/psi
42psi/9,5F/psi
43psi/9F/psi
45psi/9F/psi
46psi/8,5F/psi
49psi/8,5F/psi
50psi/8F/psi
53psi/8F/psi
54psi/7,5F/psi
58psi/7,5F/psi
59psi/7F/psi
63psi/7F/psi
64psi/6,5F/psi
70psi/6,5F/psi

 

I know you have gotten a lot of answers, but here is what I have learned and follow.

1 - Do not look at the psi numbers ON the tire - Use the numbers on the plate in the driver's door area.
2 - Check pressure in all tires when you hvae not been using the car for at least an hour or more. This gives you the psi when your tires are not heated up from the friction of driving.
3 - Yes - Check, and adjust if necessary, your tire pressure several times a year when the outdoor temperatures are changing. This will also be more important depending on where you live. Sub-tropical, where the temperature does not change much, versus living in the North, where we go from the 90s in the day to near 0 or below in the winter.

Your tires will last a lot longer if you keep them properly inflated.