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Author Topic: Tire Pressure & Direct Sunlight  (Read 1845 times)

Offline RunsinLight

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Tire Pressure & Direct Sunlight
« on: May 09, 2007, 10:21:09 am »
Is there any way that direct sunlight could cause your tires to be hot enough to raise the temperature by 5 PSI or more?

I haven't checked my tires in about a month. They should down to about 33-34. Yet I'm getting close to 40 PSI which is 5 PSI more then I have ever put in them.
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Offline tpl

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Re: Tire Pressure & Direct Sunlight
« Reply #1 on: May 09, 2007, 10:47:49 am »
According to this link, 5psi is unlikely.  So what is the difference between the sunny side and the shady side tire ?


http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=73
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Offline RunsinLight

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Re: Tire Pressure & Direct Sunlight
« Reply #2 on: May 09, 2007, 10:54:11 am »
They seem to be 38-40 all around. They should be about 34 down from 35. Haven't driven the car in about 8 hours. Its almost as if someone came along in the middle of night and put air in them.

I just left them like that. I didn't know whether to lower the pressure to 35 or not. I got the same readings yesterday as well. This is the first time I've ever seen this happen.

My last tire pressure fill-up I did use a cigarette lighter tire pump that I bought. I don't know if it has some kind of delayed reaction to it or something regarding the pressure. But the pressure said 35 when I left.
« Last Edit: May 09, 2007, 10:57:40 am by RunsinLight »
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mdxtasy

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Re: Tire Pressure & Direct Sunlight
« Reply #3 on: May 09, 2007, 10:56:53 am »
Quote from: RunsinLight on May 09, 2007, 10:54:11 am
They seem to be 38-40 all around. They should be about 34 down from 35. Haven't driven the car in about 8 hours. Its almost as if someone came along in the middle of night and put air in them. lol

Does the psi go down at night and the psi level is normal during the morning before the sun hits full strength?
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Offline Trainman

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Re: Tire Pressure & Direct Sunlight
« Reply #4 on: May 09, 2007, 10:58:44 am »
I get about 5 psi difference when doing the Pathfinder tires, sunny vs shady side.  So I just make sure that I do it early enough in the day, or on cloudy days.

Of course the Pathy tires have much more sidewall surface area than those on a typical car, so more heating seems to happen.

Also, air pressure can impact psi.  Maybe you checked them when you had a low pressure system sitting over you   :D

And was there a significant change in temperature between checkings?  That also impacts psi.
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Offline RunsinLight

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Re: Tire Pressure & Direct Sunlight
« Reply #5 on: May 09, 2007, 10:58:50 am »
Quote from: MdX5 on May 09, 2007, 10:56:53 am
Does the psi go down at night and the psi level is normal during the morning before the sun hits full strength?

Not sure. I drive at night so I've never really checked them till around 10:00 am the next day
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Offline tpl

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Re: Tire Pressure & Direct Sunlight
« Reply #6 on: May 09, 2007, 03:53:38 pm »
Are you trusting the built in gauge in your tire pump?   I have one of those and would not trust the gauge on it.   I only trust my Cdn tire mechanical gauge that has 0-40psi spread across the dial.
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Offline RunsinLight

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Re: Tire Pressure & Direct Sunlight
« Reply #7 on: May 09, 2007, 10:46:40 pm »
I use a tire gauge that was bought from the dealership. This is the first time I've ever experienced this. The added pressure couldn't have been from driving since I hadn't driving in over 8 hours. The temperature is below 20c.

Which is why I was very stumped to find the pressure near 40 PSI. I will try another one tomorrow and see what I get.

Quote from: tpl on May 09, 2007, 03:53:38 pm
Are you trusting the built in gauge in your tire pump? 
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Offline tpl

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Re: Tire Pressure & Direct Sunlight
« Reply #8 on: May 10, 2007, 06:16:48 am »
You said that you had not checked them for a month.  Depending on where you live it was COLD a month ago so that is another difference.
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Offline RunsinLight

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Re: Tire Pressure & Direct Sunlight
« Reply #9 on: May 10, 2007, 09:50:13 am »
I tried again today with a different gauge and got still got around 38-40 PSI.

It's about 6 degrees warmer the it was a month ago. Either that has changed the pressure or this cigarette lighter tire pump I used.. In order to get an accurate reading with it you need to wait a few minutes instead of checking the pressure right away.

If that makes any sense.


Quote from: tpl on May 10, 2007, 06:16:48 am
You said that you had not checked them for a month.  Depending on where you live it was COLD a month ago so that is another difference.
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Offline morty

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Re: Tire Pressure & Direct Sunlight
« Reply #10 on: May 11, 2007, 11:11:14 pm »
Any time the temperature of the air in the tire increases the pressure will go up. Warmer air expands and the volume of space remains the same increasing the pressure. Whether heated by the sun or friction the results will be the same. Now will the pressure increase as much as what you are describing? Hard to say.....but if you havent added any air and they vehicle has not been driven I guess the only answer would be increase in temperature. On Earth it is usually the Sun that does that ;)
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Offline safristi

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Re: Tire Pressure & Direct Sunlight
« Reply #11 on: May 12, 2007, 08:26:39 am »
make sure to turn the car around every half hour in the Summer to equalise the heating/pressure rises................SIMPLE EH!!!! :P OR buy some of those UGLY PLYWOOD squares to cover yer tyres..... :rofl2:

  Man it's a NON ISSUE..........ya don't see cars careening off one way or the other
 due to pressure anomalies...............I forget my Avogadro or whomevers LASWS again any high_schoolers out there   I think it was E=Mc squared... ;D
« Last Edit: May 12, 2007, 08:29:08 am by safristi »
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Offline oversteer

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Re: Tire Pressure & Direct Sunlight
« Reply #12 on: May 17, 2007, 10:58:40 pm »
Quote from: RunsinLight on May 09, 2007, 10:21:09 am
Is there any way that direct sunlight could cause your tires to be hot enough to raise the temperature by 5 PSI or more?

Yes, it's happened to me.  Don't forget also that tires are black and rims are great heat conductors.
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