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2015 Forester
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Discussion Starter · #1 ·
Autonation Subaru services both my 2018 Forester and my wife's 2015.
We noticed that when the cars got serviced this week, they set the tire pressure at 35 psi all around.
The door sticker says 30/29
I called the service manager and he said they found that the tire pressure warning light comes on at 29 in cold weather so they just set them all at 35.
I asked him if the differential pressure between the front and rear was needed and he said no. He is sending me an email to that effect.
I always thought that since the last century, the Subaru AWD system needed a differential between front and rear to work properly.
Am I having more false memories?
 

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'17 Impreza Hatchback CVT
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I could imagine that a slightly higher pressure in the front might help carry the weight of the engine, evening out the front/back tire circumference difference, but then again maybe I'm just imagining things. :grin2:

For years, I have run my tires at 36 even, all around, and have gotten much better tread wear.
 

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2015 Forester
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Discussion Starter · #3 ·
I could imagine that a slightly higher pressure in the front might help carry the weight of the engine, evening out the front/back tire circumference difference, but then again maybe I'm just imagining things. :grin2:

For years, I have run my tires at 36 even, all around, and have gotten much better tread wear.
I am with you. I was told in the last century that since the Sub has a full time AWD system, that system "wants" to see a slight wheel speed differential between front and rear. There used to be a magic fluid coupling between front and rear that controled things. Now, I imagine that there is a computer for that. But the fact remains that there IS a differential between front and rear on the door jam....so why?
Chris who likes high tire pressure.
 

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2016 XT Premium
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The only requirement as to tires and the AWD working properly is that the circumference of all the tires is very close to identical. A small PSI differential F/R has no bearing on AWD function, and a zero PSI differential F/R has no affect on AWD function

I have been running 33-35 PSI all around since new, and the AWD works fine in snow and dirt, and that isnt so much extra pressure it wears the tires funny. I wouldnt blame that shop for their tire PSI selection

You may feel the rider is bit firmer at 35 PSI, if you dont like it drop it down to 30. Dont waste your time seeking the exact spec listed in the door sill, I doubt anyone could detect the difference between 29F/30R and 30F/30R its a silly spec from Subaru HQ

If AWD was so dependent on the PSI differential it would cease to work for people all the time. PSI drifts with temperature and driving situation, and would surely drift to be identical or outside of the operative zone if AWD was so ultra-sensitive to the tires PSI.
 

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2007 Forester Sports XT 4EAT
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I could imagine that a slightly higher pressure in the front might help carry the weight of the engine, evening out the front/back tire circumference difference, but then again maybe I'm just imagining things. :grin2:

For years, I have run my tires at 36 even, all around, and have gotten much better tread wear.
As a rule, the lower the air pressure, the soother the ride, at the cost of tire tread life. Also, lower tire air pressure can = more wear from the added friction... rolling resistance = reduced gas mileage.

The factory door sticker tire air pressure is a compromise of ride comfort vs. acceptable tire tread life... tilted towards a smoother ride.

After a lot of testing, we found the "sweet spot" for our Toyo Proxes4, 235 tires is 36F/34R. :biggrin:

Bobby...
 
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2017 2.5i Fozy CVT
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I run pressures that give the most even wear across the face of the tread. A tread depth gauge comes in handy here. Load, tire size , aspect ratio, rim width, road conditions and speed all play a factor.

That said, I run 37 psi all around.
.
 

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2015 Forester
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Discussion Starter · #8 ·
36/35 summer

34/33 winter
So you DO believe in a differential? Many AWD cars and vehicles warn about replacing just one tire if the others only have half their life left. There are machines in this world that take tread off new tires.....
 

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2015 Forester
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Discussion Starter · #9 ·
The only requirement as to tires and the AWD working properly is that the circumference of all the tires is very close to identical. A small PSI differential F/R has no bearing on AWD function, and a zero PSI differential F/R has no affect on AWD function

I have been running 33-35 PSI all around since new, and the AWD works fine in snow and dirt, and that isnt so much extra pressure it wears the tires funny. I wouldnt blame that shop for their tire PSI selection

You may feel the rider is bit firmer at 35 PSI, if you dont like it drop it down to 30. Dont waste your time seeking the exact spec listed in the door sill, I doubt anyone could detect the difference between 29F/30R and 30F/30R its a silly spec from Subaru HQ

If AWD was so dependent on the PSI differential it would cease to work for people all the time. PSI drifts with temperature and driving situation, and would surely drift to be identical or outside of the operative zone if AWD was so ultra-sensitive to the tires PSI.
I have had a 2004 HOnda CR-v since new. The owners manual states a tire pressure of 26. (for ride quality). But they say if you are going to cruise at 90 mph, a practice they dont reccommend, you may set the tire pressure up to 35 to avoid heat build up in the tires. This told me that I would get better milage if I put up the pressure to 35 and cruise at 70. It works. It only stands to reason. Less flex, less heat, and bigger radium with 35
 

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I have run all my cars at 36psi irrespective of make and model, never had a problem and get good tire life.
I have owned a total of 10 cars since 1965 from Ford to GMH to Subaru & Honda.
 

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2018 Forester 2.5i 6MT
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I'm not a fan of running at 30/29. For some reason, when I see pressures in the 20s, I think of Ford Exploders having blowouts and rolling over. I usually run mine mid 30s or high 30s. I try to keep the 1psi differential, but who knows how accurate my gauges are.
 

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2014 Forester 2.5i CVT
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I set my 2014 pressures per the door frame sticker. 30/29 I think, IIRC. Works for me. Ride and handling are fine and no unusual tire wear.

TPMS will certainly come on if there is a cold snap. That is because it is doing it's job and telling you to air up!

The idea of TPMS, and most warnings, is to alert you to something that needs attention. The idea is NOT a challenge to see what we can do to defeat the warning!
 

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2015 Forester XT Touring CVT
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35/35 on stock tires here. I started from recommended 33/32 and more then 35 becomes too hard for Chicago roads. I check my tire tread occasionally and there is little less tread left in the middle of the tire which means that I was running little overinflated (I tried 36-37 as well)
I think that 1PSI higher in front is assuming that driver is alone in the vehicle (since that is the case in US for the most of the time). My vehicle usually has kids in the back and junk in the trunk so even pressure should work. I can't feel 1 PSI difference
 

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2001 Forester S, 4EAT
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Been running 35/35 on my 2001 Forester for the last 18 years...... Did not know there was a rumor that there needed to be a front/rear tire pressure differential. Never even heard of it before so that is news to me. As far as I know tire circumference needed to be within certain number of mm to keep the AWD happy.
 

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1999 A/T - 235,000 mi. WA state
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So, back to the original post, the dealer's tire air pressure of 35 psi all around is a good choice!

On different car the oil change place last week adjusted all tires to 35 psi, so maybe 35 is a standard.
 

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2016 2.5i Premium CVT
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Been running ... my 2001 Forester for the last 18 years.
18 years and running... you're my hero! Not trying to hijack the thread, but curious to know how miles you got on it so far.


Back to topic... I've been running 33 or 34 psi all around since I got my 2016. My tread wear is even and minimal. I've got about 45K miles on the current set of Bridgestone Ecopia EP422+ and still have about 7/32 of tread remaining. I have a tread guage that I use to monitor the wear.

StanF.
 

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2001 Forester S, 4EAT
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She just ticked over to 216,xxx miles. Passing it on to our son, I figure he'll get at least another 5 years/100,000 miles out of it.
 

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2018 Forester 2.5i 6MT
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Been running 35/35 on my 2001 Forester for the last 18 years...... Did not know there was a rumor that there needed to be a front/rear tire pressure differential. Never even heard of it before so that is news to me. As far as I know tire circumference needed to be within certain number of mm to keep the AWD happy.
I wouldn't say it's a rumor, it's what is on the door jamb of SJ Foresters.
 

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Sahuarita, AZ 2018 Forester Limited
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Tire shops and dealers are notorious for inflating tires much higher than the door sticker. Perhaps they assume that most drivers never check their tire pressure so they err on the safe side knowing that tires gradually lose psi over time.
 

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HCFFHC
2017 Forester 2.0XT
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253 Posts
I run 35psi all the way around. Like said above, a little rougher ride, but otherwise no problems
 
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