Ah, winter. Christmas music playing in every store, drinking eggnog without anyone judging, and long lines for the air pump at gas stations. It seems like everyone in the country decides winter is the right time to fill up their tires. Why? Are you supposed to fill your tires in the winter or something?
You shouldn’t fill your tires specifically because it’s winter. You should only fill them when your tire pressure dips below the manufacturer’s suggested tire pressure for each tire. As the air gets colder, your tires’ pressures will naturally drop. This is why you see so many cars using the air pump in gas stations during winter.
You’re about to learn all about tire pressure and how the winter changes things. Keep reading if you want to find out what’s happening to your tires when the temperature drops.
Understanding Tire Pressure
Within your tire, there is a bunch of air. The pressure of this air pushes on the rubber in your tire, blowing it up or deflating it.
When your tire pressure is “perfect”, the tire is a perfect circle. It means that the right amount of tread is in contact with the road at all times.
For reference, the tread is the textured grippy part along the middle of your tire. This tread provides a ton of friction between the tires and the road underneath. At the end of the day, this contact is the only connection between your car and the road.
If you don’t have enough or you have too much grip, your car’s performance will suffer. This is why checking your tire health is so important.
When you pump more air into your tires, you’re increasing the pressure. This becomes a lot more obvious when you’re inflating a bike tire and can physically see it expanding and puffing up.
What Cold Weather Does to Your Tires
When the air temperatures drop, the pressure in your tires changes. In fact, your tires’ psi also goes down when the temperature does.
Even if your tires are correctly sealed and there’s no hole in them (if there is a hole, learn how to patch it here), the pressure will still drop. It’s because your tire is in contact with the cold air around it which de-energizes the molecules in the air.
Sorry for the flashback to high school science, I’ll stop now. Just know that your tire pressure is going to change from season to season — yes, the opposite happens in summer and your tire pressure actually increases.
Problems with Low Tire Pressure
Some people might wonder why this is even a problem. So, what if your tire pressure goes up and down as seasons change? Well, a lot of problems occur with low tire pressure. For reference, I’m talking about pressures below the manufacturer’s suggested tire pressure.
Let’s say you slap on a nice pair of snow tires and notice that they’re 5 psi lower than the suggested tire pressure. What will you notice?
- A shorter tire life. Your tire tread will wear out quicker which means you’ll have to replace your tires more often.
- Worse fuel economy. Since your tire is connecting with too much of the road, your car is wasting energy. You’ll notice you get fewer miles per gallon over the same course.
- Longer stopping time. Your car will probably take more runway to come to a complete stop and you can expect to skid more on rainy or icy roads.
Should You Randomly “Top Off” Your Tire Pressure in Winter?
I was talking to a friend a few weeks ago and they mentioned that they top off their tire pressure every week during winter. I was blown away. They don’t check it with a gauge at all, they just assume that their tire pressure is always going down so they fill them with air until the tires “look good”.
You should only fill up your tires when the pressure is low. In addition, you should never overfill your tires. The goal should always be to have all four tires at the exact psi that the manufacturer recommends.
Overfilling is just as dangerous as underinflating your tires.
Here’s the way I see it: the manufacturer built a whole car. I’m going to defer to their judgment when it comes to how much pressure I should have inside the tires.
Ideal Winter Tire Pressure
The “ideal” winter tire pressure is the exact same as the manufacturer’s suggested rate. Colder weather doesn’t change the pressure that your tires need to be at.
If the inside jamb of your driver’s door says the front tires should be at 32psi, they should be at 32psi every day of the year.
In general, the suggested psi is somewhere between 30 and 35. The front and rear tires probably have different target values in cars that are FWD or RWD.
Don’t listen to anyone that tries to tell you to overinflate or underinflate your tires depending on the season.
Should You Fill Your Tires in the Winter?
This all leads to the big question of the day: should you fill your car’s tires in the winter? Well, it depends.
Step #1: Check Your Tire Pressure
The biggest indicator will be whether or not your tire pressure is low. To check your tire pressure, start by grabbing your handy pressure gauge.
If you don’t have one yet, I’d suggest buying one and keeping it in your glove box from now on. You never know when you’ll need it.
Go to your tire and remove the valve stem cover. This is a threaded piece of black plastic. Twist it counterclockwise and remove it completely. This should expose a brass-colored threaded piece of metal with a hole in the middle.
Press the gauge on this valve stem and you’ll get a psi reading on your gauge.
Compare the measured reading to the suggested psi value on the inside of your door.
Step #2: Check the Health of Your Tires
While you’re down there, you should check the health of your tires, too.
The first thing to look for is damage along the outside face of the tire. If you see any bubbles, large worn areas, or bulges, you should call a mechanic immediately. Damage like this can turn into a tire blowout.
Next, look at your tire’s tread. Put a penny in the tread so Abe is upside-down and facing you. If the height of the tread doesn’t cover his hat, then you’re due for new tires.
Step #3: Routinely Check the Pressure
Checking your tire pressure isn’t a seasonal activity. During the peak of summer and winter, you should try to do it at least weekly.
When you’re parked outside for more than 4 hours on an especially cold day, you should quickly check your pressure before starting your car.
In most cases, you’ll be able to visually see that your tires are deflated. Still, it’s a good idea to use your gauge to get accurate readings on your tires.
Step #4: Fill Your Tires When the Pressure Is Too Low
If at any time your tire pressure falls below the suggested value, you should fill up your tires. This most commonly happens during winter since the air is colder, as I mentioned earlier.
Even 3 psi can have some pretty major effects on how your car handles and performs.
I suggest keeping a portable tire inflator with you in your car. You can quickly grab it and top off your tires before hitting the road.
You should absolutely fill your tires in the winter if your pressure is too low. Remember, the cold air is going to naturally lower your car’s tire pressure. If you stay on top of taking pressure readings regularly, you’ll have fewer troubles this winter.
For more winter car care guides, take a look at my blog. I also have a list of products that can help you survive the cold months ahead.