Tires rotate at incredibly high speeds as you’re driving down the road, generating all sorts of friction and heat. So how hot do they get on the road?
The general rule of thumb is that tires typically undergo a temperature increase of roughly 50 degrees compared to ambient temperature after a half-hour or more of highway driving. So if it’s 50 degrees outside, then a typical tire will be about 100 degrees after being driven on.
If you’ve ever checked your tires after going for a drive, you probably felt the heat radiating off of them as you got close. But why do they get hot in the first place and how hot do they actually get? In this article, we’ll answer both of those questions as well as how heat can affect tire pressure, and more.
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How Hot Do Your Tires Get While You Drive?
After you get done driving for an extended period of time, most parts of your car are far hotter than they were before you took off. Engine? Check. Transmission? Check. Brakes? Check. What about the tires? Do they actually get hot while you drive, or is that heat that you feel radiating from the wheels and tires really from the brakes behind the wheels?
Don’t get me wrong, the brakes do get very hot from driving. Especially under hard braking conditions. So never touch your rotors after you get done driving! But that heat isn’t just from the brakes, the tires do, in fact, get hot while driving. Most of the time they’re not going to be so hot that you’ll be burned or anything like that, but they definitely get warm from normal driving conditions.
As I go through this, keep in mind that the actual temperature change that tires undergo while driving depends on the type of tire, its size, the rubber compound, the weight of the vehicle, speed, and more. But for a standard tire on most passenger vehicles, there is a simple rule of thumb that most people in the automotive world follow, as explained by Car and Driver in this post surrounding the issues with Firestone tires from the early 2000s.
The tule of thumb is that a typical tire will undergo an increase in temperature of about 50 degrees after being driven on for a half-hour or longer under normal highway driving conditions. This change of 50 degrees is relative to the ambient temperature. So if it’s a cold 30-degree morning and you drive for a half-hour on the highway, you can expect your tires to be about 80 degrees to the touch.
Again, this rule is not suitable for every tire under all conditions, but it gives you a general idea of how hot your tires get.
What Causes Tires To Get So Hot?
This change in tire temperature while driving is the result of two main things that all tires experience while you’re driving: flexing of the tire and friction. When I’m talking about the flexing of the tire, I’m referring to the way in which the part of the tire that is in contact with the road is flattened in that instant, but then immediately unflattens once it’s off the road.
And when a car is moving at highway speeds, tires are undergoing hundreds of rotations per minute. This means that the tires are being repeatedly flattened and unflattened again and again, hundreds of times per minute. This movement generates heat and contributes to the temperatures of the tires rising.
As mentioned above, the other main contributor to the temperature of the tires rising is the friction caused by the tire rubbing against the road, as touched on in this article. Rubber and asphalt are dissimilar materials, and one rotating against the other at high speeds generators excessive friction which will eventually lead to the tire getting hotter and hotter.
When you combine the effects of flexing with the effects of friction, you come up with the ways in which tires get hot as you drive on them.
Does Heat Affect The Pressure In Your Tires?
You might have noticed over the years that your tire pressure always seems to suddenly be lower than expected when the weather gets cold for the first time. This is due to the temperature outside dropping, which is of course roughly the same temperature of the air inside the tire if the car hasn’t been driven for a few hours.
The general rule of thumb is that there is a change in tire pressure of 1 psi for every 7-10 degrees that the temperature changes. This works both ways. So if it gets cold overnight and the temperature drops 40 degrees, you can expect your tires to be about 4-5 psi lower than they were before the temperature dropped. And if the temperature outside increases by 40 degrees, your tires will likely show about 4-5 higher psi than before.
Well, this same thing happens when you drive your car and the tires heat up.
The recommended tire pressures that you can find on the tire information placard on the inside of the driver’s door show what the tires should be set at. And those pressures are for when the tires are cold. This is why it’s important that you check your tire pressure when the tires are cold, i.e. when you haven’t driven the car.
To see why this is important, let’s first take the information from earlier in the article into account about a tire’s temperature increasing by about 50 degrees after a half hour or more of highway driving. Combine that with the rule of thumb you just read about how temperature affects tire pressure, and you can see where the issue may arise. That 50 degree change in temperature can lead to a change in pressure up to 5-6 psi.
So if you were to check your tires right after a long drive and the pressures seem to be right at the recommended values, you might think everything is good to go. But remember to subtract ~5 psi from what pressure they’re at and you might see that they’re actually low after all. So keep this in mind during your monthly tire pressure check!
About THE AUTHOR
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding