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2010 Forester Limited
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24 Posts
Discussion Starter #1
Just checked tire pressure for the 1st time since buying the Subie (yes I know I should have done it a lot sooner) and all 4 tires are set at 46 PSI. The label inside the door says 32. So I have been driving over-inflated. Have I done any damage to the tires (2200 miles)?
Do I go ahead now and let some air out? How will that affect the ride? We leave for vacation tomorrow.
I have the '10 automatic non-turbo with the Geolander tires. (Sorry guys I can't remember all the initials you use).
 

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2007 Forester Sports XT 4EAT
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38,739 Posts
Quick answer, no permanent damage & your ride will be smoother with the correct air pressure. :smile:

Curious, did you check the air pressure when the tires were cold? If tires are check hot after being driving, or having the sun heat them up, will give you a false higher tire pressure. I like to check my tire pressure early on the weekend before driving or the sun has time to heat then up. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2006 XT Limited 4EAT
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4,793 Posts
Quick answer, no permanent damage & your ride will be smoother with the correct air pressure. :smile:

Curious, did you check the air pressure when the tires were cold? If tires are check hot after being driving, or having the sun heat them up, will give you a false higher tire pressure. I like to check my tire pressure early on the weekend before driving or the sun has time to heat then up. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
How big of a difference is there between hot and cold pressure? i.e. Could it read 46 lbs/in^2 hot and then cool off and read 32 lbs/in^2. Fresh out of Honors Chemistry this year, I know some formulas for gas pressure, but come on, its summer vacation! :shrug:
 

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2007 Forester Sports XT 4EAT
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Cold to me means not having been driven, no direct sun on the tires & the tires are cold to the touch. If you check the air pressure once a week, you'll most likely add or remove a small amount of air. I use a bicycle air pump to add air. :wink:

There can be several pound difference from one side to the other, if the sun has been heating up the tires on one side. :icon_eek:

BTW, summer here in Oregon means rain... expected thru the week & turning the heating system back on! :frown:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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Premium Member
2004 Forester 4EAT
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5,462 Posts
Probably a difference of a few pounds cold to hot. Verify your guage before you do too much.
 

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2005 Forester XT 4eat
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4,583 Posts
How big of a difference is there between hot and cold pressure? i.e. Could it read 46 lbs/in^2 hot and then cool off and read 32 lbs/in^2. Fresh out of Honors Chemistry this year, I know some formulas for gas pressure, but come on, its summer vacation! :shrug:
Not very likely. I usually don't see much fluctuation over 5-6 psi. Also, you will see less fluctuation with high cold pressure. Tire deflection from under inflated tires causes them to heat up a lot.
 

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2010 Forester Limited
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Discussion Starter #7
I will check the pressure again while the tires are good and cold. I had driven about 2 miles about 30 min before I checked it tonight. It is only in the 70's now after being 90 this morning.
 

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2004 Forester 4EAT
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Cold to me means not having been driven, no direct sun on the tires & the tires are cold to the touch. If you check the air pressure once a week, you'll most likely add or remove a small amount of air. I use a bicycle air pump to add air. :wink:


Bobby...

Really?! You're more A.R. than me.
 

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2007 Forester Sports XT 4EAT
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I will check the pressure again while the tires are good and cold. I had driven about 2 miles about 30 min before I checked it tonight. It is only in the 70's now after being 90 this morning.
I usually check mine in the morning. Our vehicles park outside & even if the sun is on the tires, it won't make that much difference. It's not a perfect science & it doesn't need to be perfect... for most of us. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2007 Forester Sports XT 4EAT
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Do you guys know anything about the little electronic pressure gauges? More or less reliable/accurate than their traditional counterparts?
I used to use those sliding stick air pressure gauges, which I always thought were inaccurate. Then I bought a cheapo digital one, which fell apart when I was trying to change the battery... I think that how it was designed! :mad: I found the one below on eBay & I love it! It's way more than you need, but it's perfect for me. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2010 Forester Limited
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Discussion Starter #13
I used the pencil type tire gauge, same one I use on my motor scooter.
Thanks for all the input. I don't understand 99% of the things you all discuss most of the time but you sure do help this newbie!
 

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2007 Forester Sports XT 4EAT
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Keep in mind, as long as you were under the maximum inflation pressure that printed on the side of the tire, the only side affect of higher tire pressure is a rougher ride & perhpaps better gas mileage. For an extended amount of miles, you may get some odd wear. Keep in mind some member run their tire pressure close to 40 psi or higher.

One last thought. The listed air pressure on the door is a factory compromise for a smooth ride, good handling & resonable tire life. It basically a starting point, which you can change to suit your driving requirements. For me, 36F/34R is the sweet spot for my performance tires, wheels & upgraded suspension. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2006 FXT 6MT
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2,669 Posts
My forester's recommended COLD pressure is 31 front/ 29 rear. However, I keep it significantly higher than that in the front because of how and where I drive. Knowing a little about consequences of running high/low pressures helps this logic make sense. Since I drive in Colorado mountains; very spirited at that; cornering is pretty hard on my tires. This is the reason I got the tires I got for this summer:

http://www.zerotohundred.com/newforums/attachments/chassis-and-wheels/132303-wts-205-55-16-zr-bf-goodrich-gforce-sport-tire-98-new-bfgoodrich.jpg

Now, because over-inflated tires will have a slight bulge in the center of the tread, all that hard cornering sort of negates that center wear in a sense. Yes, I have to change my air pressure very often, usually before AND after I drive, depending on where I plan to go, but the also helps with even tread wear. Tire rotation is also very frequent. For normal city/freeway driving, I run about 34 cold front, 32 rear. For mountain driving and fun roads, I increase them to 38 cold front, 33 rear. Obviously the rear tires don't take quite such a cornering load as the fronts, so I don't need such a significant pressure increase. But like I said, I will return the pressures to the standards when I am done driving in the mountains or whatnot. Yes, it's time consuming and whatnot, but it equates to the terrific mileage I can get and tire longevity.
 

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2010 Forester 2.5X Premiu
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83 Posts
Do you guys know anything about the little electronic pressure gauges? More or less reliable/accurate than their traditional counterparts?
I've read the digital gauges can fail to perform in extreme cold (battery gets too cold, LCD doesn't like extreme cold).

I've always used the stick type, but I just picked up this one and REALLY like it.


The owner's manual gives a guide to adjusting for tire pressure/use/temp.
 
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