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Low Tire Pressures #4540348 10/11/17 03:23 PM
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SatinSilver Offline OP
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Filled up some newer Nokians to 34 psi a few weeks ago. Someone commented one of the front tires looked low. Checked the tire pressure and it read 28.5 psi. Checked all tires and they all read 28.5 on the digital tire pressure gage. When I filled them to 34 it was after some hwy miles on a hot day. The tires have an "A" temperature rating. Hoping I don't have leaks around the rim. Had them installed at QuickLane who took his time and one of the best according to the advisor.

Re: Low Tire Pressures [Re: SatinSilver] #4540363 10/11/17 03:34 PM
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oil_film_movies Offline
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You lose 1 psi per 10 degrees F due to physics of gases (air). Also, driving around generates heat and pressure too. You put in 34 psi on a hot day after some driving. So attribute about 2 psi to driving around heat generated, and 4 psi due to 40 degrees hotter that hot day, and you just demonstrated physics. Deflategate all over again here.... no scandal.
Knowing that, one can adjust their thinking about tracking pressure.
Also, sometimes its the Schrader valves, not the tires.

Last edited by oil_film_movies; 10/11/17 03:36 PM.
Re: Low Tire Pressures [Re: SatinSilver] #4540366 10/11/17 03:37 PM
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Kestas Offline
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If faulty and leaky, I doubt all four tires would lose air at the same rate.
We've recently had temperature swings going from 80s to 60s.
Also, you mentioned filling them to 34 after hwy driving on a hot day. That'll go down to a lower number in cooler weather.

It's best to check tire pressures in the morning before driving and before the sun warms them.

Re: Low Tire Pressures [Re: oil_film_movies] #4540371 10/11/17 03:41 PM
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SatinSilver Offline OP
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Thanks, they put in new valve stems when tires were installed. Since all tire pressures were the same I thought that was a good sign. Car is outside all the time and has had a fair amount of hwy miles put on it recently.


Re: Low Tire Pressures [Re: SatinSilver] #4540392 10/11/17 04:02 PM
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Eddie Offline
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I set my tire pressure before driving in the morning. I use a good gauge. As stated tires increase or decrease in pressure at a rate of ~ one psi for every 10 degree f. change in temperature. Ed


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Re: Low Tire Pressures [Re: SatinSilver] #4540408 10/11/17 04:32 PM
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Rand Offline
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Tires can lose around 1psi a month normally, also 1psi per 10f

my tires were going from 36 to 40 while driving..
well outside temp dropped and suddenly they were at 32-33 36 after extended driving.

Also these firestone destination AT seem to lose abit more air than other tires I've had previously.

If its the 2005 with alum wheels.. they can lose quite abit of air from bead seat corrosion.. but all of them dropping the same makes that unlikely.


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Re: Low Tire Pressures [Re: SatinSilver] #4540413 10/11/17 04:44 PM
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Keep in mind that the sidewall rating is "COLD" so even at what most refer to as "max sidewall" it's still designed for expansion. I usually only see about 3 PSI swing on my Cruze's TPMS from morning/cold to the peak of a mid-day highway run, but that they all dropped consistently sounds much more like expansion/contraction than leakage.


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Re: Low Tire Pressures [Re: SatinSilver] #4540460 10/11/17 05:47 PM
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Originally Posted By: SatinSilver
When I filled them to 34 it was after some hwy miles on a hot day.


That's it right there.

Re: Low Tire Pressures [Re: Merkava_4] #4540490 10/11/17 06:25 PM
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gaijinnv Offline
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Here's a page from a Toyota TSB you might find helpful:



HTH


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Re: Low Tire Pressures [Re: SatinSilver] #4540687 10/11/17 09:09 PM
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oil_film_movies Offline
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gaiginnv, I've never seen a chart like that. Kudos to Toyota. However, its too complicated for the average John Q. Public out there.
Its even able to fool us because the "O deg F" shown on the left vertical axis is really the DIFFERENCE between room temperature and the ambient outdoor temperature you are checking the tire at, NOT 0 deg F winter temperature.
Want it complicated a bit more(?): A tire parked in shade vs. a tire in full sunlight will read about a couple of psi different.

In summary: The B-pillar placard temperature is really the 70 deg F pressure. Now add or subtract 1 psi for how hotter or colder the ambient air temperature is, and put the tire in the shade (no sun), and let the tire cool for at least a couple of hours after driving. Still too much for people to follow. Soccer moms don't want any of this.

Re: Low Tire Pressures [Re: oil_film_movies] #4540804 10/12/17 12:17 AM
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gaijinnv Offline
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Originally Posted By: oil_film_movies
gaiginnv, I've never seen a chart like that. Kudos to Toyota. However, its too complicated for the average John Q. Public out there.
Its even able to fool us because the "O deg F" shown on the left vertical axis is really the DIFFERENCE between room temperature and the ambient outdoor temperature you are checking the tire at, NOT 0 deg F winter temperature.
Want it complicated a bit more(?): A tire parked in shade vs. a tire in full sunlight will read about a couple of psi different.

In summary: The B-pillar placard temperature is really the 70 deg F pressure. Now add or subtract 1 psi for how hotter or colder the ambient air temperature is, and put the tire in the shade (no sun), and let the tire cool for at least a couple of hours after driving. Still too much for people to follow. Soccer moms don't want any of this.


Just about all of that is incorrect spank


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Re: Low Tire Pressures [Re: SatinSilver] #4540815 10/12/17 01:04 AM
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Nick1994 Offline
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Same thing recently happened to me. The Sonata's tires were around 29 psi which I usually keep at 36. But my Jeep's tires were still at 35 psi shrug but it sleeps in the garage all the time.


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Re: Low Tire Pressures [Re: Nick1994] #4540849 10/12/17 04:55 AM
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Right after I put some Cooper's on my Buick they were losing 2-4 pounds every 3 or 4 weeks which I thought was a little excessive but after a while this stopped. Now I only need to adjust them 3 or 4 times a year. I'm not sure what happened here but I'm guessing they sealed better or settled on to the rims over time due to the rims being old or dirty.


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Re: Low Tire Pressures [Re: gaijinnv] #4541070 10/12/17 10:23 AM
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oil_film_movies Offline
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Originally Posted By: gaijinnv
Just about all of that is incorrect spank
If you still disagree with Toyota, then I suggest you go back and study engineering. The Toyota chart is correct. What parts of it are you not understanding?

Re: Low Tire Pressures [Re: oil_film_movies] #4541239 10/12/17 02:03 PM
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SatinSilver Offline OP
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Thank you everyone for the comments. Some very good points were made. Checked the psi this morning of just one rear tire and it was 34.5. When I filled all the tires yesterday to 35 they were warm from getting off the highway, maybe 10 miles. Temp yesterday was in the low 70's. I only checked one tire this morning since I didn't feel like checking all of them. I will check them again next week.

My mom commented the other week the front tire looked low. Which is why I checked it. When I saw 28 psi I thought for sure I'd be taking it in for a leak repair at Discount Tire. But when all of them had the same psi I knew that probably wasn't the case.

A week or two ago we saw some temps in high 30's and some highs in upper 80's. Plus a fair amount of hwy driving. Probably about 2000 during the last air fill up.

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