Tire pressure cold vs. warm

[LDB]

About how much does tire pressure change from overnight sitting cold to warm after driving and about how many miles of driving does it take to warm up? I drive almost entirely locally at speeds below 45mph, mostly below 40mph. I go to Discount Tire for pressure adjustment and trying to figure out how much above the door plaque number to have them set as they will have a short drive of warming up on the way.

 

[GSCJR]

When tires are not cold, it's easy to remember, as it rhymes:

Add four to the door.

 

[vavavroom]

Air pressure changes about 1 PSI per every 10°F. As the tires warm up, internal air pressure increases. How warm your tires get depends on various factors. "

Generally speaking, you are looking at an increase of no more than a few PSI.

 

[Brybo86]

I always set them cold first thing in the morning.
If checked after driving around they are usually 3-4 psi higher.

 

[LDB]

Thank you for the replies. I think I'll just have them set 3psi over the door when I go. That should be close enough to the door when they fully cool.

 

[eljefino]

Do you not have your own pressure gauge? I'd go 5 over then bleed down next morning if you need to.

 

[DriveHard]

When tires are not cold, it's easy to remember, as it rhymes:

Add four to the door.

I always was taught it should be +10% when warm...so 4 is about right, erroring on the high side, which is what I would prefer.

Even if you check them in the morning, it needs to be in the dark. If the sun is out and shinning on one side, that side will be higher, as black tires suck up that sun's energy.

 

[Rand]

Do you not have your own pressure gauge? I'd go 5 over then bleed down next morning if you need to.

exactly. if its a hot day and hot tires from driving
cold next morning 3psi might not be enough.
go 5 over then adjust next morning cold.

 

[LDB]

Do you not have your own pressure gauge? I'd go 5 over then bleed down next morning if you need to.

Nearing 70 I no longer have a tire gauge, at least where I know where it is. I should, but it's easier to drive up and get them to take care of it.

 

[Tdog02]

Drive to Discount Tire and let those young folks set your pressure with their machine. They have young knees and backs that still obey the brains command. The key thing is consistency. Provided you are around the correct pressure. I was gonna buy one of the pressure machines till I saw how much they are.

Even if you didn't buy there, Discount Tire will check your pressure and will give you a report card on the tread depth. They are a good company with competitive prices if you need new tires. They don't like anything lower than 4/32 tread depth for repairs. They are a victim of their own success and are usually busy from open to close. Tire pressure line will get you in and out quickly unless there are multiple cars ahead of you.

 

[LDB]

Yes, I go to DT and they set whatever I ask. It is almost exactly 1.5 mi. from the house with no traffic lights going and only 2 returning. Couldn't be much more convenient.

 

[jadatis]

Its not difficult but complicated.

If you use yust enaugh pressure for the load and speed used, the tire inside gascompound rises to about 60 degr C/ 140 degr F on a ambiënt temperature day of 20 degr C/ 68 degr F.

How long it takes ???? Mayby 15 minutes when driving that speed constantly.

The pressure-rising is related to the temperature rising in tire.

At the bottom I will give a list of degr F temp rise per 1 psi rise .
Assuming measured cold at 70 degrF, but if you use it for 60 degr F cold , it wont give dramatic differences.
Yust for easy calculating by head using pressure from tpms .does not have to be super-acurate.

Now your recomended pressure is for 160 kmph / 99 mph or max technical carspeed given , and fully loaded.
You wrote to drive 45 mph max and not constantly, and probably only driver , so lower load and speed then pressure is needed for.
So it will take longer to get mayby only 40 degr C / 104 degr F in tire , with the pressure-rising belonging to that.

Here the list.
then you see that between 35 and 42 psi , you can use the often given 1 psi per 10 degr F.

70degrF./degrF/psi

20 psi/ 15,5F/psi

21 psi/ 15F/psi

22 psi/ 14,5F/psi

23 psi/ 14 F/psi

24 psi/ 13,5F/psi

25 psi/ 13,5F/psi

26 psi/ 13 F/psi

27 psi/ 12,5 F/psi

28 psi/ 12,5 F/psi

29 psi/ 12 F/psi

30 psi/ 12 F/psi

3 1psi/ 11,5 F/psi

32 psi/ 11,5 F/psi

33 psi/ 11 F/psi

34 psi/ 11 F/psi

35 psi/ 10,5 F/psi

36 psi/ 10,5 F/psi

37 psi/ 10 F/psi

39 psi/ 10 F/ps

40 psi/ 9,5 F/psi

42 psi/ 9,5 F/psi

43 psi/ 9 F/psi

45 psi/ 9 F/psi

46 psi/ 8,5 F/psi

49 psi/ 8,5 F/psi

50 psi/ 8 F/psi

53 psi/ 8 F/psi

54 psi/ 7,5 F/psi

58 psi/ 7,5 F/psi

59 psi/ 7 F/psi

63 psi/ 7 F/psi

64 psi/ 6,5 F/psi

70 psi/ 6,5 F/psi

71 psi/ 6 F/psi

77 psi/ 6 F/psi

 

[LDB]

Yes, definitely complicated. Not sure I comprehend it all but maybe when not the middle of the night.

 

[02zx9r rev2]

I always go 1-2 over what sticker on door jamb says

 

[tbm5690]

As a cold climate individual I have to set about 5 psi over target in the winter in my heated garage, and the tires never recover to that pressure regardless of how long I drive until I'm back in the garage in the coldest month. Reverse math is hard!