[Electroharmonix]

Hello everybody,

I got my '14 Forester 2.5i a few days ago and I want to know the right tire pressure for the stock tires. I cant find this information in the user manual :icon_confused:

Actually I live in Richmond VA, the temperature here is not that cold in winter but I'm gonna spend the next few months in Minneapolis, MN. Do i need to change tires pressure or definitely need snow tires?

Thanks :icon_cool:

 

[xtn]

Open driver's door and you should be able to find tirepressure information

Last time i put 2.4 bar since temperature change's can be very high here. 10C change is equal to 0.1 bar drop in pressure

 

[GeoJosh]

Yes, you will find the tire pressures listed when you open the drivers door and look around.

It should be something like 32-34 psi. They probably came overfilled from the dealership/delivery, so make sure you check them soon.

 

[xtn]

2.4 bar converts to 34.8 psi. Bit higher than recommendations. But keep in mind that when temperature drops, so does tyre pressure

 

[crewzer]

Hello everybody,

I got my '14 Forester 2.5i a few days ago and I want to know the right tire pressure for the stock tires. I cant find this information in the user manual :icon_confused:

Actually I live in Richmond VA, the temperature here is not that cold in winter but I'm gonna spend the next few months in Minneapolis, MN. Do i need to change tires pressure or definitely need snow tires?

Thanks :icon_cool:

Congratulations on your new Forester, and welcome to the forum!

Tire pressure info for the U.S. 2014 Forester is contained in OM Section 9, Specifications, page 12-9. As noted above, it's also found on the label at the bottom of the driver side "B" pillar.

Everything else being equal, tire pressure drops along with ambient temperature. So, you'll likely need to air up a bit when you initially move to a colder region. The time to check tire pressure is first thing in the morning after the car has sat outside all night. Checking winter pressue in a relatively warm garage typically results in a false high reading.

I live in western NC, and I alrerady have my winter tire and wheel set installed. For me, there'd be no question about a winter set if I was to spend the winter in Minneapolis.

Related threads:

http://www.subaruforester.org/vbulletin/f72/dunlop-sp-winter-sport-3d-61799/
http://www.subaruforester.org/vbulletin/f72/winter-driving-tires-chain-advice-needed-260546/​

HTH,
Jim / crewzer

 

[aimlower]

The door jam on my 2014 2.5i Ltd reads: 30 psi F, 29 psi R. That's what gave it the lovely ride we bought it for. After the 10km service it road like a turnip truck. The mechanic had decided (dealer practise) to make it 35 all around (+20%) because of the season. I had him change it back. There is no mention of adjusting for cold from the engineers behind the 30/29 psi door jam notice. The tires @30/29 feel hard and then warm up quickly here in the winter. Softer tires flex more and cause heat, that's why under inflation wears out tires in the Summer. So, what actually is the tire pressure/temperature effect in a moving tire in Winter? The static one is mentioned elsewhere. My car moves. The temp changes during the day, and from day to day. "Tire Science" has to be one of biggest scams around. Do I actually want to bounce along endlessly (listening to winter tires roaring if installed) for a slight, unspecified advantage in what, handling, tread life...safety? 30F/29R it is: See you in the Spring.

 

[Electroharmonix]

Thanks everybody, i found the info at the driver door. Recommended pressures for my car (and all 2.5i?) are 30 Front / 29 Rear. My current pressures are 33 Front / 32 Rear, it's fine for winter time i guess as the temperature drops?

@crewzer: I have never been in a region with heavy snow before and I'm not a skilled driver so I will seriously consider a set of winter tires once i get there. But i have to find a place to store the wheels first

 

[crewzer]

So, what actually is the tire pressure/temperature effect in a moving tire in Winter?

The real goal is to optimize operational (warm) tire pressure, and the idea is that that goal will be achieved when starting out from a "cold" pressure reference.

Tire pressure increases as the car is driven and the trires warm up, regardless of season. However, due to colder environmental conditions, the total pressure increase in winter may be ~4 psi lower than in summer.

Personally, I run my Forester's tires at 34/34 cold in the "warm" months, and 36/36 in the "cold" months.

Tire Rack has a nice discussion on this topic.

HTH,
Jim / crewzer

 

[crewzer]

Recommended pressures for my car (and all 2.5i?) are 30 Front / 29 Rear. My current pressures are 33 Front / 32 Rear, it's fine for winter time i guess as the temperature drops?

Personally, I think the slightly higher cold pressures are a good idea for several reasons:

1) I find the higher pressures more comfortable and more communicative. Specifically, I like the better feel.
2) The tires don't warm up as much in the winter as they do in the summer. Higher cold pressure will help them reach the optimal operating pressure.
3) The TPMS sensors' low trigger point is ~26 psi, so you want to allow some margin for low cold pressure resulting from dramtic ambient temperature drops.​

For example, it's -4F this morning at my brother's house in Maine. :icon_eek:

Regards,
Jim / crewzer

 

[aimlower]

"In most parts of North America, the difference between average summer and winter temperatures is about -50° Fahrenheit...which results in a potential loss of about 5 psi as winter's temperatures set in. And a 5 psi loss is enough to sacrifice handling, traction, and durability!

…Next we evaluated the effects of heat generated by the tire's flexing during use. We tried to eliminate the variable conditions we might encounter on the road by conducting this test using our "competition tire heat cycling service" that rolls the tires under load against the machine's rollers to simulate real world driving. We monitored the changes in tire pressure in 5-minute intervals. The test tires were inflated to 15 psi, 20 psi, 25 psi and 30 psi. Running them all under the same load, the air pressure in all of the tires went up about 1 psi during every 5 minutes of use for the first 20 minutes of operation. Then the air pressures stabilized, typically gaining no more than 1 psi of additional pressure during the next 20 minutes."

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

It appears that if your winter morning tire pressure is 25 psi, you should be in the door sticker range within 20-40 minutes since the test didn't specify ambient winter temp as affecting the tire-generated heat factor. Even driving to a pump causes a 2 psi difference. I don't find all that "science" particularly helpful. If, as I experienced, having them inflated to 35 all around has me HAMMERING over the road, the notion that the tire performance is enhanced remains unconvincing. I think Tire Rack just missed providing any hard data on what actually happens to a moving tire in winter. That's what the issue is, not what people just think sounds right.

 

[crewzer]

I don't find all that "science" particularly helpful. If, as I experienced, having them inflated to 35 all around has me HAMMERING over the road, the notion that the tire performance is enhanced remains unconvincing. I think Tire Rack just missed providing any hard data on what actually happens to a moving tire in winter. That's what the issue is, not what people just think sounds right.

So, what have you decided to do, and why?

Regards, and welcome to the forum!
Jim / crewzer

 

[aimlower]

So, what have you decided to do, and why?

Regards, and welcome to the forum!
Jim / crewzer

"30F/29R it is: See you in the Spring" until I get an answer to exactly how much my winter-cold tires change when driven; there seems to be a lot of guessing going on. My primary concern is ride quality. I would not have purchased a vehicle which road the way mine was returned to me. Anyway, as presently inflated I appear to be living longer and have for years . Thanks for the welcome, Regards, aimlower

 

[adc]

So, what have you decided to do, and why?

Regards, and welcome to the forum!
Jim / crewzer

I personally think aimlower is overanalyzing things (no disrespect) If you do as crewzer suggests you should be way more than fine. I actually try to keep mine 34psi front/rear all year around (cold) but honestly I don't notice much of a difference until the front gets around 38+ psi -hot. Then it seems to squirm around.

Jim makes a good point of putting it a bit higher in winter bc the pressure won't get much greater than the cold reading.

Perhaps you are using a bad gauge. Consider a dial gage and actually I have two so I can verify that they are probably both reading close to the same pressure.

 

[crewzer]

"30F/29R it is: See you in the Spring" until I get an answer to exactly how much my winter-cold tires change when driven; there seems to be a lot of guessing going on.

There are a lot of car-related topics that involve a lot of guessin'. :icon_wink:

This topic is of particular interest to me, so I'll try (to remember) to take some winter and summer measurements in order to facilitate a more objective discussion.

In the meantime, I'm comfortable -- both phyically and logically -- with my 36/36 cold winter pressure setting.

Regards,
Jim / crewzer

 

[adc]

. I think Tire Rack just missed providing any hard data on what actually happens to a moving tire in winter. That's what the issue is, not what people just think sounds right.

If you are looking for good numbers you can use the Ideal Gas Law with pretty good accuracy. The best accuracy would be obtained by picking a specific temperature and pressure......that is what you seem to be looking for.

It works like this:
TC = Cold temp (F) + 460
PC = Cold pressure(psi) + 15 (Psi)
TH = Hot temp (F) + 460
PH = Hot pressure(Psi) + 15

PH = TH/TC x PC

As an example: If the outside temp is 20F (Winter) and your tire pressure is 30 psi...you want to know what the pressure will be if the temp goes up 1 degree F.

PH = (481/480) x (45) = 45.094 psia
This means that for every 10 F increase the tire will go up .94 Psi..call it a pound
...........................................................................
At 80 degrees:
PH = (541/540) x (45) = 45.083
This means that for every 10 F increase the tire will go up .83 Psi..call it a pound

So really the information you see published is fairly accurate. 10 degree rise in temp equals 1 psi.

More accuracy can be obtained but I doubt anyone cares :N_poke:

As far as what happens to a moving tire. That depends on surface temperature (of the road) and also speed. If you want to get a good idea..purchase a cheap infrared heat gun to get the temp of the tire. I'll do that tomorrow morning and report back. As ridiculous as my post is, I am now curious. :icon_wink:

 

[aimlower]

More accuracy can be obtained but I doubt anyone cares :N_poke:

I don't doubt the data on static air pressure and temp changes. On the other hand, everyone seems to care enough to be recommending things, dramatically, in many cases: Do something seems to be the metric. I notice, too, that no one bothers with the 30/29 front to back tire pressure ratio suggested by the engineers. Right, what do the engineers know? (OK, starting Monday everyone's mortgage goes up 3%.) It appears that everyone is just doing what they feel comfortable doing and/or throwing in a little tirerack.com patter for support. Me, too.

All the best,
aimlower...

 

[tiptoptune]

Can anyone at or near sealevel confirm they can run door jamb specified pressure 32 frt 30 rr on 2012 or similar and not have light on?

Thanks

 

[Majorlk]

Can anyone at or near sealevel confirm they can run door jamb specified pressure 32 frt 30 rr on 2012 or similar and not have light on?

Thanks

300 ft ASL, my '10 with OEM G95s (255/55/17) run 32/30 without the light coming on. Can't imagine the '12 would be any any different. The light isn't supposed to come on until the pressure drops to 25 lbs, as far as I know.

 

[Rio Dog]

Whoa...

As a new Forester owner and participant in these forums, I am really impressed by both the quality and quantity of responses. In the short time that I have read through the various threads that pertain to questions or issues that I have been having, I'm already starting to realize that I completely underestimated the Subaru customer base, a lot of smart folk.

That being said, I'm a black and white kind of guy. That is, for certain questions, like what my tire pressures should be, there shouldn't be a fuzzy gray area, or anything more than rudimentary scientific analysis required to figure out what my tire pressures should be. SO much information in this thread but I am utterly confused and overwhelmed. So let me take a step back...

I've owned vehicles and personally maintained tire pressures on a regular basis on them for 25 years give or take. I've always used various information and resources to arrive at the optimal tire pressures for all of those vehicles, but in the end, there WAS a figure. ONE figure. I never had differing tire pressures for front or rear tires. And I never adjusted tire pressures differently for hot or cold weather, and I live in the Northeast where the temperature has been and continues to be anything but consistent. Even with the "err in my ways", knock on wood, I've never had a flat, blowout, inconsistent or early advanced tire wear, load balancing or weather related issues, etc. I've even maintained tire pressures for a boat trailer with spare for the past 15 years, again, without issue, knock on wood So while I know very little about the science behind what the optimal pressure for a given tire should be at any given time of the year, I know how to read a door jamb, I know that various built-in and external gauges and air pumps can often be inconsistent, and I know how to talk to a variety of people and resources to get a good idea as to what the tire pressure (not pressures) should be on all four tires and/or a spare for any given vehicle.

So here is my plan for my new Forester:

1.) Order a pair of the same decent quality, reasonably priced manual dial gauges (I think I paid $20 x 2 for an AccuGage model with solid reviews on Amazon, should be here on Wednesday).
2.) Check the driver's side door jamb for the official Subaru notification on what the tire pressures should be -- 30 front, 29 back, 60 spare - yeah, that's not going to be happening
3.) Call the service department of the dealer where I purchased the Forester tomorrow and ask them point blank a.) what the tire pressures all around SHOULD be, b.) what the tire pressures are that they typical put into demo and/or sold cars that get operated throughout the dealership (if different), c.) what the mins/max the Yokohamas can handle, and d.) how on earth am I supposed to access the spare and check its pressure, how often am I supposed to do that, and is it really 60 PSI?
4.) Call my local mechanic for his experiences and recommendations on the Yokohama Geolanders that came stock with the Forester
5.) On Wednesday or whenever the tire gauges arrive, take back to back cold measurements all around, including the spare if I can figure out how to access it, because right now everything feels perfect.
6.) Take the Forester around the corner to my favorite free automatic air machine, which is less than a mile away, and the gauge on which is general off by 1 PSI +/-, then adjust all the tires up/down to some figure along the lines of the various recommendations in this thread. My initial thoughts are to go with 34 front, 34 rear, all year round, but that really depends on what the readings are before I start tinkering, and how the tires feel afterwards.

Sometimes it is best to keep things simple. I'm not building the Space Shuttle here. I just need the "correct" tire pressure for my new car, how hard can that be?

 

[adc]

Personally, I run my Forester's tires at 34/34 cold in the "warm" months, and 36/36 in the "cold" months.

That is precisely what I do. Keep all 4 the same and use your rationale about the temp increases when driving based on the outside temp.

Great minds think alike :icon_wink:

I notice, too, that no one bothers with the 30/29 front to back tire pressure ratio suggested by the engineers. Right, what do the engineers know? .

Front and back are based on calculations on handling (possibly) and GVW...now right off the bat you know that you, your passengers and load will not meet the criteria the Engineers used...Their calculations would change based on the load and temperatures on any particular day. So worrying about the difference front/back with these variables and using a gage that is probably more than a psi off makes no sense (to me)