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2017 2.5i Premium Auto
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Discussion Starter · #1 ·
Going on a road trip tomorrow and went to check the tire pressure and noticed the tires have a max of 51! Owners manual was 32 and 33 I think. Where are they supposed to be? In the middle somewhere, or stick to the 32-33? Thanks!
 

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Discussion Starter · #3 ·
29 and 30! That seems awfully low, but I guess Subaru knows what they are doing.
 

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I reckon around 34 is good, a little less in the rear unless carrying a heavy load. A good check for tire pressure is that there should be a 4 psi increase when hot; if less than 4 psi then cold pressure is too high, if greater than 4 psi then cold pressure is too low.
 

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Discussion Starter · #5 ·
I reckon around 34 is good, a little less in the rear unless carrying a heavy load. A good check for tire pressure is that there should be a 4 psi increase when hot; if less than 4 psi then cold pressure is too high, if greater than 4 psi then cold pressure is too low.

That sounds like a good test, I'll check that tomorrow. Thanks!
 

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'17 Impreza Hatchback CVT
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My 2017 Impreza was delivered with the tires at 47-48 psi. I dropped them to 36-38 and run that. I have a TPMS display and see the pressure rise a few psi when I drive around town and/or park in the sun.

With my old Forester, tire wear was terrible at the placard rating and improved when I ran them in the mid 30s. MPG is better too.
 

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Discussion Starter · #7 ·
My 2017 Impreza was delivered with the tires at 47-48 psi. I dropped them to 36-38 and run that. I have a TPMS display and see the pressure rise a few psi when I drive around town and/or park in the sun.

With my old Forester, tire wear was terrible at the placard rating and improved when I ran them in the mid 30s. MPG is better too.
Yeah it seems like a little more pressure would make a big difference in tire wear and gas mileage. I don't have a display, but I can sure drive for a while, then stop and check. Thanks!
 

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'21 ISM Crosstrek Limited
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This is good reading:

Determining the Right PSI - Tire Review Magazine

This excerpt was new to me and correlates with my and others' empirical personal standards:
Part of each load curve standard is the point at which the load curve stops going up. For TRA p-metric standard load tires, it is at 35 psi. Equivalent ETRTO and JATMA tires peak at 36 psi.
My choice of tire pressures has varied but almost always ended up between 3-5 psi over recommended, landing around 34-35 psi as maximum, with one psi more in the front. Tire wear is always even.

My '17 FXT's recommended pressures are 33F and 32R (but like all the others was delivered with 40+). Subaru, at least, seems to be learning as earlier cars had lower numbers and took more increases. So, on the FXT I only use two psi over, and maintain them at 35F 34R... religiously.

First day home after delivery the tires are first to be addressed, and always need adjusted. Next are the lug nuts, each wheel loosened then torqued to spec with a torque wrench. Then oil level, fluids, etc. to establish a confidence base level in my new vehicle. Ownership.
 

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2018 Crosstrek
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Dealers like soft tires for comfortable ride. Soft tires wear badly on the edges. Maximum tire life requires even wear across the tread. That is usually found 2 to 4 psi above the spec on the car door post. It can take some experimenting to find the sweet spot for handling and long life.

The important considerations are: 1. never run under inflated because that causes over heating and can be dangerous. 2. side-to-side balance is necessary for handling.

If you have the time read The Wheel & Tyre Bible.
 

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The dealers over-inflate to give max MPG, so customers will go whoo-ah, look at the MPG I get from my new Subie! I use the door placard suggested pressures. If you think the car ride too wishy-washy, then go up a couple pounds from the door placard pressures.
 

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The dealers over-inflate to give max MPG, so customers will go whoo-ah, look at the MPG I get from my new Subie!
They do that after you buy it. When they are selling they are under inflated. To be fair, cars sit on the lot for a long time and that may have something to do with it.
 

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Discussion Starter · #12 ·
Little late getting back on here...... I set them at 34 and called it good. I didn't check them on the road like I should have.... I ended up averaging 34mpg for the 2000ish mile trip. That included hwy mainly, a little interstate, and some in town driving. I was happy with it. The car did great.
 
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