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Old 11-01-2001, 07:11 PM   #1
TheWRX
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Question normal tire pressure loss?

How quickly would you expect a healthy tire to loose pressure? I measured the recommended 32 psi in one of my front tires maybe around 4 weeks ago, and it was down to 29 psi today. Does that seem like an excessive pressure loss, or just that I should be checking much more frequently?

It has also gotten considerably colder over the last few weeks, could that make a significant difference? I did measure after the car had not been driven for a few hours both times.
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Old 11-01-2001, 07:36 PM   #2
dave1rr
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Quote:
It has also gotten considerably colder over the last few weeks
That would account for most, if not all of the loss. And it's not uncommon for alloy wheels to slowly loose air. I'm not suprised at a 1-2 psi/month loss in my tires.

You're fine, just check the air pressure every week, especially when the temperatures are changing like they have been.
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Old 11-01-2001, 07:44 PM   #3
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I agree. Aluminum wheels especially will lose air durring colder periods.
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Old 11-01-2001, 07:49 PM   #4
vvk
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Consumer Reports just did a test of tires. They determined that tires loose from 2 to 6 psi in 6 months.
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Old 11-01-2001, 11:13 PM   #5
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When it goes from 85-95F weather to 35F weather and back to 85F weather in 4 days which it does often around here, my tires will go down from 40PSI to 30PSI.

You *should* check your tire pressure everytime you fill up your gas tank. However, I know zero people who do this. Hell, I'm the only one I know who even bothers checking tire pressure at all!
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Old 11-02-2001, 01:04 AM   #6
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I've heard that you lose 1 psi per every 10 degress decrease in temperature.
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Old 11-02-2001, 01:17 AM   #7
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I think I have magic Re92's on magic stock rims, cause I haven't had to put air in my tires since I got the car. All within one psi of each other. Need to kick my dad's retired a$$ bimmers out the garage one day so I can get a level surface to measure on and fill them properly, but really, no problems with air pressure in 10 full months. Magic I tell you

I know the trunk monkey isn't keeping the pressures up to par, cause i don't have one:monkey: but it's on the christmas list.

(Hmm. Maybe I should throw Capt. Cornelius the space monkey in there?)
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Old 01-25-2009, 09:20 PM   #8
Smp928s
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I have noticed that when it is cold out my 08 Impreza will lose considerable tire pressure on long drives at high speeds. It happened in 1 tire, I took it in to have it looked at and the problem went away (or was corrected). It has since starting happening in another tire.

For example the other night I left my home and it was 25 degrees out. I was at 32psi when I left. I got on the highway and began traveling at 65-75 mph for 15 miles or so. My pressure warning light came on and I got off the highway. I was down to 20psi just like that. It was now 10-15 degrees out. I filled the tire back up and within another 20 miles it was down to 17psi. This sequence occured one more time until I got to my destination and filled the tires back up. The car sat for 3 hours in near 0 degree weather. When I came back to the car the pressure was fine, no loss. I drove home a little slower 60-62 for nearly 60 miles and experienced no probs. For the last 20 miles or so I increased my speed back to 70-75 and again no problems. The next morning, after sitting 8 hours again no pressure loss.

Obviously I will have this looked at again (I am starting to get frustrated with this car, this is the 3rd of 4th time this has happened). I am not a physics minded person and have average mechanical inclination. Can someone explain to me what is going on here? Is it the tire's seal with the wheel?

Thanks
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Old 01-25-2009, 10:42 PM   #9
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Quote:
Originally Posted by Smp928s View Post
I have noticed that when it is cold out my 08 Impreza will lose considerable tire pressure on long drives at high speeds. It happened in 1 tire, I took it in to have it looked at and the problem went away (or was corrected). It has since starting happening in another tire.
I'm having the same problem with my wife's LGT. Everytime she goes on a longer drive at higher speeds (65 or over) she looses air in two tires (RF and LR). It's only started happening after it has gotten cold out. I've taken it in twice now and had the tires dismounted and resealed and it has not fixed the problem. I've got a aftermarket TPM system installed which shows the tire pressure in each tire in real time, so I can watch the pressure as it falls. The only thing I havn't tried is to remove and replace the valve stems which have the TPM sensors built in. That will be my next step. FYI new tires and TPM system where installed in May of 08. Problem with pressure loss did not start until 11/08. I had the tires remounted 12/08 and again 1/09. I sent a PM to Luke at the TireRack (where I bought the tires and TPM system) to see if he had any suggestions but he never replied.
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Old 01-25-2009, 11:28 PM   #10
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^^re last 2 posts: that's not normal. I couldn't tell you what though.

PV=nrT so yes temperature matters.
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Old 12-04-2009, 12:45 AM   #11
09WagonRX
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Quote:
Originally Posted by Mike Wevrick View Post
^^re last 2 posts: that's not normal. I couldn't tell you what though.

PV=nrT so yes temperature matters.
Ditto, thank you G-Chem , and you thought you wouldn't ever use the stuff you learned in college. I 2 have lost tire pressure with sudden temp drops to 46F and the very next day back to 80's so I dug this thread up. I feel at ease that my car isnt the only one loosing tire pressure. It just seemed weird that my wife's corrola hasn't lost tire pressure and is also equipped with tmps so i got a little paranoid about maybe I had ran over a nail or something.

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Old 12-04-2009, 09:18 AM   #12
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Quote:
Originally Posted by paulnose View Post
I think I have magic Re92's on magic stock rims, cause I haven't had to put air in my tires since I got the car. All within one psi of each other. Need to kick my dad's retired a$$ bimmers out the garage one day so I can get a level surface to measure on and fill them properly, but really, no problems with air pressure in 10 full months. Magic I tell you

if you have had any temperature variations more than maybe 40 degrees or so, something else is up. ("In this house, we obey the laws of thermodynamics!") Do you take your car in for oil changes? I'd also start to suspect the gauge.
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Old 12-05-2009, 10:32 AM   #13
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Quote:
Originally Posted by redobs View Post
I've heard that you lose 1 psi per every 10 degress decrease in temperature.
A better way to say it is, "Air pressure in a tire will change 1PSI for every 10*F change in temperature."

Thus if the temp changes down 40*F, you will see a tire pressure drop of 4PSI.

Tires will also lose (not loose) air over time, a few pounds/month is normal not counting in air temp changes. Some tire places use Nitrogen rather than air, the larger molecules seep through the tire at a slower rate.
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Old 12-05-2009, 01:45 PM   #14
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and some tires are WAY more prone to to lose of pressure over time than others

I have had fresh mounted tires that lost pressure very rapidly and predictibly....and some that didn't need adjustment for many months
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