Why Your Tire Pressure Light Comes On Every November
Short answer: air contracts as it cools. Every 10 °C drop takes roughly 1–2 psi out of each tire. Pressures you set in September are genuinely low by the first cold snap — the light is telling the truth. Top them up to the number on the door jamb and it’ll clear.
Where to Find the Right Number
Two places have numbers on them, and only one is correct.
- The sticker in the driver’s door jamb — this is your car’s specified pressure. Use this one.
- The sidewall of the tire — this is the maximum the tire can hold, not what your car wants. Setting to this makes the ride harsh and wears the centre of the tread.
Most passenger cars sit between 32 and 36 psi. Some SUVs and vans specify different front and rear figures, and a few list a higher pressure when the car is fully loaded. The sticker covers all of it.
How to Check It Properly
- Check cold. Before driving, or at least three hours after parking. Twenty minutes of driving can add 3–4 psi and give you a false pass.
- Use the door-jamb figure, not the sidewall maximum.
- Do all four, plus the spare if it’s a full-size one. The spare is the tire nobody checks until the day it matters.
- Drive a few minutes so the TPMS re-reads. If the light is still on after twenty minutes of driving, that’s not pressure — that’s a sensor problem.
Temperature or a Real Leak?
Easy to tell apart:
- All four down by a similar amount, after a cold night — temperature. Top up and carry on.
- One tire down while the others are fine — a leak. Could be a nail, a perished valve stem, or bead corrosion on the rim.
- Same tire keeps going down every couple of weeks — definitely a leak, and the slow ones are usually the rim, not the tire. That’s a $75 bead reseal, not a new tire.
Why It’s Worth Bothering
An under-inflated tire flexes more, runs hotter, wears its outer edges and gives you a longer stopping distance in exactly the conditions where you need a short one. It also costs fuel — or range, if you drive an EV, where it’s one of the cheapest range improvements available.
Check monthly. It takes five minutes and it’s the single highest-value thing you can do for a set of tires.