Tire pressure/temperature/ and throw in altitude

[Squantobon]

Watched a yt video the other day with some rv tips and one was to NOT prepare for a trip by setting the tire pressure the night before but in the morning because tires are to be set cold.

Well, that's hardly always the case. Right now it's 1pm here and 51 degrees. About 8pm, 55 is predicted, and 10am tomorrow (about the time we'd be leaving if leaving tomorrow) 62 is predicted. So, I think this is a good rule of thumb.

But there's another factor of Boyle's Law I don't hear discussed nearly as much. We are now at about 7,200'. Our next destination will be about half that and so we will arrive with under inflated tires. And some trips have far more significant altitude changes. Periodically, along our journey, we should check and adjust our tire pressures but it takes 2-3 hours for tires to properly cool down. So how do most people deal with altitude changes and tire pressures? I could see a rapid climb being somewhat dangerous. Is there a tire temperature that should be cause for concern?

[Chargerman]

Don’t overthink it. Check pressure with the tires cold and forget it. If you change altitude or temp zone significantly then check and adjust when the tires are cold again.

[wolfe10]

No question temperature affect PSI. Yes, indeed, PV=nRT!


Elevation/altitude-- very little.


But, in most cases, high elevation= lower ambient temperatures.


That is why we head to the mountains for the summer!

[MrMark52]

X3 ^^ What they said!

[Camp CA]

X4 ^^ what they said.

I will add....left home at sea level with tow vehicle and trailer tires inflated to target pressures. Drove over 3 ~7000 ft passes over the course of a week and now at 5600 ft elevation all the tire pressures are nearly the same as we started out. Tire pressures are checked/monitored before/during each travel day but rarely have to make any adjustments.

[jadatis]

Recently made a pressure/temperature calculator for dry gascompound, and if enaugh water in tire. In that last I am the first, I think.

In that you can also fill in the ambiënt pressure, wich you then can use for altitude, but have to caculate the ambiënt pressure change for altitude yourselfes.

If you want to play with it, mail me at my hotmail.com adress with username jadatis, and I will send it in return. Combine yourselfes my mailadress, spamm robots cant this way.

But the difference for altitude is that marginal, that if you determined your pressure with enaugh reserve, you dont need to worry.

And I read an article wich suggestes that the absolute pressure determines the deflection of tire, so exagerated ambiënt pressure vacuüm, still same deflection.
Needs more research, but if true, fill at higher altitude pressure calculated back to sealevel, is a bit higher measured pressure, and for every altitude you are OK.

Then the temperature in tire.
Cold pressure is when temperature inside tire is practically the same as when outside the tire.
That is when not driven long enaugh, and no external factors like sunshine on tire.
That last has become the definition.

My idea is to calculate the pressure back to a reference temperature, and wrote a long article about it why.
In short when hot, say 100 degrF outside, lesser cooling down of tire material, but also lesser heatproduction, because lesser deflection by the higher pressure.
Then certainly dont lett off air otherwise more heatproduction.
When cold the other way around, but then highening up pressure is allowed for fuelsaving and riding quality.

The " tirespecialists" on this forum dont agree with this amateur, so do with it what you think best.

So to my opinion, you can lett the cold pressure flow with ambiënt temperature, easyer system.

[Chargerman]

Why complicate a simple process. Fill cold and drive

[jadatis]

But people dont think that way, at least I dont.
Once you know how it works, in the end it comes down to fill cold and go.
But never blead down cold or warm pressure, only fill up.

Unless it verry cold, you then lett the lower pressure exist, or if wanted highen up.
But then when suddenly 100 degrF outside, pressure is to high. Then only blead down to what it would calculate.

For on the road I made next list.
In that search the pressure you determined to be needed. Then remember the degrF/1 psi with it, and in the road you can calculate by head roughly what you have to measure.
Accurate enaugh for the goal.
Then mostly it will give, dont change pressure, easy.

Cold70degrF/ degr F./1 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
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi
149 psi/ 3 F/psi
177 psi/ 3 F/psi

[MrMark52]

Originally Posted by Chargerman

Why complicate a simple process. Fill cold and drive

^^ X2!

Originally Posted by jadatis

But people dont think that way, . . . .

I don’t.

I check cold tires for pressure in every morning - then drive.

I don’t get real worried about change in altitude or temperature in a single day of driving. If it was such a major issue, there would be cars, 8 wheelers and tire carcasses littered all over the roads.

[Chargerman]

Originally Posted by jadatis

But people dont think that way, at least I dont.

Once you know how it works, in the end it comes down to fill cold and go.

But never blead down cold or warm pressure, only fill up.



Unless it verry cold, you then lett the lower pressure exist, or if wanted highen up.

But then when suddenly 100 degrF outside, pressure is to high. Then only blead down to what it would calculate.



For on the road I made next list.

In that search the pressure you determined to be needed. Then remember the degrF/1 psi with it, and in the road you can calculate by head roughly what you have to measure.

Accurate enaugh for the goal.

Then mostly it will give, dont change pressure, easy.



Cold70degrF/ degr F./1 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

71psi/6F/psi

77psi/6F/psi

78psi/5,5F/psi

86psi/5,5F/psi

87psi/5F/psi

96psi/5F/psi

97psi/4,5F/psi

109psi/4,5F/psi

110psi/4F/psi

126psi/4F/psi

127psi/3,5F/psi

148psi/3,5F/psi

149psi/3F/psi

177psi/3F/psi

Sure looks like your over complicating it. Throw that list away.

[jadatis]

When I read the reactions in post #9 and #10, I wonder how topicstarter dares to ask about it.
And somehow this topic dwaw your atention, so the subject must interest you in some way.

[Gr8bawana]

Originally Posted by Squantobon

Watched a yt video the other day with some rv tips and one was to NOT prepare for a trip by setting the tire pressure the night before but in the morning because tires are to be set cold.

Well, that's hardly always the case. Right now it's 1pm here and 51 degrees. About 8pm, 55 is predicted, and 10am tomorrow (about the time we'd be leaving if leaving tomorrow) 62 is predicted. So, I think this is a good rule of thumb.

But there's another factor of Boyle's Law I don't hear discussed nearly as much. We are now at about 7,200'. Our next destination will be about half that and so we will arrive with under inflated tires. And some trips have far more significant altitude changes. Periodically, along our journey, we should check and adjust our tire pressures but it takes 2-3 hours for tires to properly cool down. So how do most people deal with altitude changes and tire pressures? I could see a rapid climb being somewhat dangerous. Is there a tire temperature that should be cause for concern?

You're overthinking it.