Winter/summer tire pressure

I was talking to a lady friend who has a mid-00s Subaru Forrester. She had replaced the OEM tires with off-road tires which she purchased from Les Schwab. She told me that during the summer she should maintain her tire pressure at 30 psi but in winter she should maintain it at 50 psi. Can this be correct? I know tires need to be monitored more often for pressure during the winter because the cold temperature causes more rapid pressure loss, but I always considered this to be a reactive thing instead of a proactive thing.

No experience with that vehicle, but it sort of seems on the extreme side. Colder ambient air will cause the tires to deflate a little compared to summer I suppose, but years ago when I lived in Colorado I tended to prefer a reduced tire pressure, as it provided a little better traction on snow covered roads.

Where did she get that nonsense ? There is a door plaque that gives what the tire pressure should be .

I don’t think so.
Tire pressure goes up and down with temperature.
Pressure should be adjusted to the same pressure in hot or cold weather, when the tires haven’t been driven on for several hours.
The label on the driver’s door frame and the owner’s manual tell what the pressure should be with the original (size and type) tires.

I check and adjust tire pressure once a month in the morning before driving.
I note the temperature and if I expect a colder morning in the next month (typical in the fall) I add 1 psi for every 10 degrees F colder it might get.

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After 4 years had tpms error. Filled em up to 33, light still on. Left it at the airport, got home, toyota says should be 35 psi, though the door panel says 33. Never had to air them up before. After 1 week all at 33 psi , 1 at 28, 2 at 30 and one at 33. So I filled em up to 35, light off and still good 3 weeks later. Mystery to me.

Back in the seventies I checked my tire pressure whenever I felt like it. About half past never.

When I saw a low tire I would air it up. Expensive tires cost about $70 each but I usually bought used ones and almost rotated them now and then. On the plus side; there was no TPMS virus going around and brakes worked a lot better. Our steering wheels would never explode and our seat belts would never cause a fire. You could buy two cars for the price of a catalytic converter.

I’m talking too much because it’s kind of scary to ride in these rolling bombs they make today. Oh, the only bumpers that were held on with rope were on the back of a 74 rusty LTD. Enough for now.

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I forget which car, had disc brakes big circle in the center of the brake pedal, man that cars brakes were so strong, it took a while to learn to lightly touch the pedal!

Back to the original question, she should still use the tire pressure specified by Subaru. 50 PSI is probably getting near the maximum pressure for the tire. The “off-road” tires are likely just a more aggressive tread pattern than her OEM tires with no other internal design changes.


There is some theory among experienced winter drivers that a higher tire pressure in winter assists the tire to punch through the snow layer to reach pavement. Something about a smaller contact surface, harder tire, and what not. But none of those people would say to go from 30 to 50 psig, probably more like 30 to 35 or maybe 38 psig.
Maybe @Bing would weigh in on this.

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Many Toyotas have a “reset” button for the TPMS. My impression is that this button resets the system to think that the current tire pressures are correct, and then the warning light will illuminate if any pressure drops about 2 psi from the setting. So if you want the pressures to be 33 psig, adjust all the tires to that cold pressure, then use the reset button in accordance with the user manual.

I’d be very surprised if that’s true. That would be dangerous.

Back to original question, NO! Always use the door sticker value, when measured before driving.

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From my user manual:
Initializing the tire pressure warning system (U.S.A. only)
■ The tire pressure warning system must be initialized in the following circumstances:
● When rotating front and rear tires which have different tire inflation pressures
● When changing the tire size
When the tire pressure warning system is initialized, the current tire inflation pressure is set as the pressure benchmark.

It then goes through the procedure of how to use the reset button to “initialize the TPMS”.

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50 psi seems like the maximum pressure listed on the tire, and I wouldn’t go anywhere near that. If she checks every one or two weeks, then using the pressure on the door plaque and in the owner’s manual is good. If she checks less frequently, then two or three psi over the Subaru recommended pressure should be OK. That allows for some leakage or temperature related pressure change over a month or so interval between checks.

I guess I’m surprised. But it’s not just a “button “, right?

Yep a pushbutton that you hold down for a few seconds under specific other conditions with the ignition key and whatnot. It would have to be intentionally reset, couldn’t be sabotaged by a passenger while driving or anything like that.

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Filled the tires up to 35 and the light went out right away. No reset switch for smart key models. If it is happy at 35 I am happy. The warning light went out right after I got the last tire up to 35psi.

Higher pressure means harder not softer tire on the road. If you think harder tires “punch through the snow” why not try bike wheels or model T wheels to test the theory. To me, more tire on the road means more traction but suit yourself.

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I agree with you, but have not noticed a difference in ride. AWD so not concerned at this point about traction. Those model ts had some pretty incredible videos though in mud and with snow skis.

I hope Capriracer chimes in.
My understanding correct tire pressure keeps the tread open.
In the bias ply days, reduce PSI for drag racing, increase PSI for road course. Rockcrawlers will reduce pressure to allow tires to conform to the surface of the rocks.
Street use of radial ply, run the recommended pressure.

Interestingly the guys around here who ride bikes in the winter have the wide tire versions. The bike tires are 3-4" wide with knobby tread instead of the standard narrow tires. Pretty expensive I guess but who rides in the winter anyway?