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TIRE TIPS // MAINTENANCE

Tire Pressure in Cold Weather

THE SHORT ANSWER

Tire pressure falls about 1 psi for every 5°C drop in temperature, so a warm October afternoon turning into a minus fifteen morning takes several psi out of every tire. Set them cold to the number on the placard inside your driver's door, and check them monthly through the winter.

BY THE RIM2RIM CREW PUBLISHED SEPTEMBER 3, 2026 4 MIN READ

The number behind the light

Air contracts as it cools. Transport Canada puts the working figure at about 7 kPa, roughly 1 psi, for every 5°C drop in temperature.

Do the arithmetic on an Alberta autumn. You set your pressures on a pleasant plus fifteen afternoon in October. Three weeks later you walk out to minus fifteen. That is thirty degrees, which is about six psi gone from every tire, and a tire that was at 35 psi is now sitting at 29.

Nothing leaked. The tires are simply cold. This is why the entire Foothills gets a dashboard light on the same morning every November, and why the shop phone rings all day.

Where to find your number

The placard inside the driver's door jamb lists the cold inflation pressures your vehicle was designed around, front and rear, sometimes with a separate figure for a loaded vehicle.

That is the number. The figure moulded into the tire sidewall is the tire's maximum, not your target, and setting to it gives you a hard ride, a worn centre strip and less grip.

Cold means cold: before the vehicle has been driven, or at least three hours after. Driving heats the air and adds several psi, so a pressure set at a warm gas station after a highway run will be low the next morning.

What underinflation actually costs

Grip first. An underinflated tire rolls onto its shoulders, which changes the contact patch and blunts turn-in and braking, on ice worst of all.

Then wear. Chronic low pressure wears both shoulders and leaves the centre, and it can take thousands of kilometres off a set.

Then fuel. Low pressure raises rolling resistance, and the effect across four tires is measurable over a winter of commuting to Calgary.

Then heat, which is the dangerous one at highway speed. An underinflated tire flexes more, flexing makes heat, and heat is what destroys a tire on a long run. That is the mechanism behind most highway blowouts, and it is why trailer tires deserve a check before every trip.

Overinflation has its own costs: a harsh ride, a centre-worn tread and less grip, because the contact patch is smaller than it was designed to be.

What TPMS does and does not tell you

Most vehicles built in the last fifteen years carry a tire pressure monitoring system. Direct systems use a sensor inside each wheel. Indirect systems infer a low tire from wheel speed through the ABS sensors, which means they detect a soft tire but cannot tell you a number.

Two limits are worth knowing. Transport Canada notes that some systems warn only when a tire is significantly underinflated, at which point the tire may already be close to failure, so the light is a late alarm rather than an early one. And large temperature swings set the light off on their own, which in chinook country happens several times a winter.

Treat the light as an instruction to check all four with a gauge, not as a measurement. A five dollar gauge in the glovebox is still the most useful tire tool anyone owns.

Sensors themselves have a life. The batteries are sealed in and typically last five to ten years, and the service kits, the little seals and valve cores, want replacing when a tire is dismounted. That is what a TPMS service covers, and it is why a sensor sometimes dies during a changeover rather than because of one.

A winter routine that takes five minutes

Check pressures monthly, and always after a big temperature swing. In the Foothills that means after every chinook, in both directions.

Check them cold, first thing in the morning, at home rather than after a drive to the station.

Set to the placard, not to what is in the tire now and not to the sidewall maximum.

Do the spare, if you have one. Spares are usually the softest tire on the vehicle and are only ever needed at the worst moment.

Watch the pattern. If one tire always needs more, it is not the weather, it is a leak, and most of them are repairable.

Nitrogen, and the honest version

Nitrogen migrates through rubber a little more slowly than air and holds pressure a bit more steadily across temperature swings, mostly because it is dry and carries no water vapour. That is a real if modest benefit, and it is why we offer nitrogen fills.

It is not a substitute for checking your pressures. Air is 78 percent nitrogen already, and a tire filled with nitrogen still loses pressure when it gets cold. Anyone selling it as a way to never check your tires again is selling you something else.

Quick answers

Why did my light come on with no leak? Cold. About 1 psi per 5°C, so a hard overnight drop pulls several psi out of every tire.

Can I just add air until the light goes out? Add air until the gauge reads the placard number, then the light should clear after a short drive. Do not chase the light past the correct pressure.

Should I run higher pressure in winter? No. Run the placard pressure, measured cold.

How often should I check? Monthly, and after every big temperature swing.

Do I need to reset the system? Some vehicles relearn on their own after a few minutes of driving, some need a tool. We do the relearn as part of any changeover.

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