Does the Chart in this Link Make Sense?!

Scroll 1/2way down and examine the chart in this article on tire inflation:

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According to that chart, if one owns a car where OEM factory pressure is, I.E. 32psi at 70degrees ambient outdoor, if the outdoor ambient temperature is only 40 one should inflate their tires to 35psi cold. If outoor ambient is 20degrees, inflate to 37psi cold.

WTF?

-ChrisCoaster

Reply to
ChrisCoaster
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ChrisCoaster wrote in news:d111b0af-02cf-4251-a28e- snipped-for-privacy@h2g2000vbd.googlegroups.com:

Air drops in pressure in concert with drops in temperature. In other words, when air gets colder it gets smaller, just like everything else (except water once it gets below 32F).

You lose about one pound of air pressure for every ten degree drop in temperature Fahrenheit (one of the wonderfully easy-to-remember features of Imperial measure).

Thus...

There's 30 degrees difference between 70 and 40. That means you need to add three pounds to the pressure you had at 70 in order to maintain that same gauge reading at 40.

32+3=35.

There's 50 degrees difference between 70 and 20. That means you need to add five pounds to the pressure you had at 70 in order to maintain that same gauge reading at 20.

32+5=37.

It works in reverse as well, so in spring you need to bleed pressure off as the ambient temperature rises.

Reply to
Tegger

Tegger wrote in news:Xns9CABD495146ABtegger@208.90.168.18:

To clarify: Both the page you reference and my post assume 70F as a constant when determining how much air to add to obtain the correct pressure.

A hopefully illustrative example: Assume you had filled a tire to 32psi at 70F ambient. The temperature then drops to 40 overnight. If you should check the pressure with the ambient being 40, you would find the gauge to read 29 and not 32. Thirty degrees drop in ambient temperature results in three pounds drop in tire pressure. You now need to add three pounds to bring the tire pressure back up to 32 at the ambient temperature of 40.

Clear as mud?

Reply to
Tegger

68.18:

Muddier than mud!

Whether the temperature is 20, 40, or 80F, I just add what I need to get the tires up to(in my case)- 31psi. I don't compare the needs of a tire when it's 70 degrees out to when it's only 40, etc. I just make sure the damn gauge reads 31psi cold from January to July, and add or subtract what air I have to to get it there.

-CC

Reply to
ChrisCoaster

lol.

I understand what the chart is saying, but how many times do you get up in the morning and say "Hun, you need to put 39psi in the tires cause we're gona drive to the North Pole today!" lol

The way it reads, in the winter your your supposed to put 37 lbs in to get 32! LMAO We all know you just gotta check the air pressure. Check it cold, and and it will change as the seasons change. But no matter what season, 32 psi is 32 psi.

Reply to
twisted

____________________ In a way, I do sort of what the chart says - but on a monthly basis. In December, I'll set the tires to 33psi so I don't have to worry about them again until February. The average temperature here drops

10-15 degrees between mid-December to late January, so I'll end at 31-31.5 psi by that time. It teaches you to think - and set - ahead.

-CC

Reply to
ChrisCoaster

ChrisCoaster wrote in news: snipped-for-privacy@r31g2000vbi.googlegroups.com:

Uh-oh, Google Grouper! Ugh.

That's all I do.

Summer and winter I can set the tires to one pressure and then leave things alone.

Spring and fall, when temperatures fluctuate wildly, I use particular temperatures as baselines. Currently it's 40F, which is about median for my area at this time of year.

Knowing the relationship between temperature and pressure, I inflate so that at 40 my pressure is what I desire it to be. Should the temperature rise to 60, I know the tires will be 2# overinflated. Should it drop to 20, they will be 2# underinflated. Neither deviation from the median is at all unsafe, or even detectable in normal driving, so I've got lots of leeway before I need to make my next gross adjustment.

In January I use 0F as my baseline. In July I use 80F.

Reply to
Tegger

Tegger wrote in news:Xns9CABD495146ABtegger@208.90.168.18:

Yes, but their numbers are backward:

37 psi-> 20 degrees 32 psi -> 70 degrees 35 psi -> 40 degrees

Now the numbers would yield

42 psi @ 70 degrees 32 psi @ 70 degrees 37 psi @ 70 degrees

Hence the OP's point I believe.

If it goes below zero overnight get ready for a loud bang(s) coming from the garage.

Reply to
fred

Uh, that's what he just said.

Reply to
E. Meyer

My Uncle Al says that you can't put too much air in a tire, that you should just keep pumping until you can't get any more air and and then it'll be fine. Surprisingly, he's still alive.

--scott

Reply to
Scott Dorsey

"Remember; you can't put too much water in a nuclear reactor!" - SNL

Reply to
Heron McKeister

Seems to me, 36 PSI is 36 PSI. Summer, winter, equator or North Pole...

Reply to
Hachiroku $B%O%A%m%/(B

Be nice if it loaded...

Reply to
Hachiroku $B%O%A%m%/(B

How many tires has he blown off the wheels?

I saw a guy do that ojne time. I was across the street, driving 35 MPH and I thought my daughter was going to wet herself, it was so loud.

Of course, I *NEVER* wet myself...

BANG!!!!!!!!!!!!

Reply to
Hachiroku $B%O%A%m%/(B

It's a very funny chart! :-)

Reply to
dsi1

Here's my take on what they are trying to say. What they are trying to take into account, I think, is that when you drive the car the tires will heat up and that will cause the pressure to go up but that as the temperature drops below the 70 degree baseline it doesn't heat up as much. It's not stated anywhere but it's implicit in how the chart is set up that they expect a tire at 70 degrees to gain 7 psi when it's fully warmed up. So the warmed up running pressure will be

7 degrees higher then the recommended cold inflation pressure. So as you look in the chart, for example for 32 pounds, they are increasing the recommended cold pressure you should use as the temperature drops. At 40 degrees they are saying put 35 pounds in when it's cold because you won't gain the 7 pounds at the temperature, you'll only gain 4 pounds but if you put in 35 pounds you still get the same running pressure of 39 pounds, the same as you would have gotten if it was 70 degrees and you put in 32 pounds. It does make sense, it's just not well explained.
Reply to
Ashton Crusher

________________ Well, I'll be damned if I'm going to put in a higher cold tire pressure in January than I do in July! Most people just aren't going to be thinking like that, unless they're piloting a 767 from Puerto Rico to NYC in winter.

Besides, rubber tends to "harden" at lower temps, so the ride is already harsh at the car mfg's recommendation(in my case, 30psi). So why I'd have to put 34(or 35 or 36)psi in my tires in winter makes no sense, whether the air inside 'em expands more in summer or in winter. 8 o So, July or January, into my Kia's tires goes 32psi (to prevent shoulder wear and tighten up handling), and everything's alright as far as my ride is concerned.

-CC

Reply to
ChrisCoaster

Air molecules are thicker in warm weather. You can lead a Horse to water, but you can't make him drink. cuhulin

Reply to
cuhulin

___________ Alright, so I'm bad because I plan to keep my tires at 30PSI(or a hair above) in winter and summer. So what?! At least I don't let them plummet to 25 or 20psi by February the way at least half of the general public probably do.

And so what "air molecules are thicker in warm weather". Are you trying to say that the 30(31)PSI my gauge indicates in winter is not the same as the 30PSI it indicated in summertime? Man, the 60s must have been good to you!

-CC

Reply to
ChrisCoaster

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