All-season tires: How they work & when you need them

When most drivers think about "normal" tires, they're thinking about all season tires. So, what makes a tire all season, and what other seasons of tires are available?

All season tires are designed to perform reasonably well in a variety of weather conditions like rain and light snow. The sidewall of an all season tire will usually have the letters M and S, which stand for mud and snow. An M+S or similar marking indicates that the tire's tread pattern has grooves designed for mud and light snow.

How All Season Tires Work

The main benefit of an all season tire comes down to the tread pattern-the grooves and other shapes molded into the tire's tread. The whole reason these grooves are there is to maintain contact with the road when things like rain, mud, and snow start to get in the way.

It's easier to understand how an all season tire is designed for all seasons when you see it side-by-side with your other main options: summer tires (also called 3-season tires) and winter tires.

Summer tires tend to have a simple tread pattern designed for rain.

Winter tires have very aggressive tread patterns for deep snow, slush, and ice.

All season tires are good for rainy springs and summers, cool falls, and mild winters.

Summer and winter tires have other features like rubber compounds designed specifically for warm or cold temperatures, but you can't really see these in a picture.

When All Season Tires Aren't for All Seasons

So, you have all season tires, and you think you're good to go, whatever Mother Nature throws at you. A reasonable assumption, right? Not quite. There are two situations where your all season tires just won't be up to the challenges that they'll face on the road.

Worn Tires

The added grip of all season tires comes from the grooves in the tread pattern, so it makes sense that those grooves can't do their job if they're worn down. The truth is that an all season tire that's only half worn may have already lost a lot of its snow grip.

At a tread depth of 6/32″, a typical tire is about 50% worn. And with grooves that are only half as deep as they used to be, it's conceivable that the tires may only be providing half the all season grip it used to. Some regions even have seasonal road restrictions that allow all season tires in the winter but only if the tread is still 6/32″ or deeper.

This is just a complex way of saying that all season tires will eventually reach a point where they're not good in the snow anymore.

Freezing Temperatures & Ice

All season tires are good on mud and light snow. In addition to snow, winter also brings freezing temperatures. If it doesn't usually get below 45 degrees where you live, then all season tires are a good choice. If winter is a little more brutal in your neck of the woods, all season tires may not be your best option.

In cold weather, the rubber compounds in an all season tire start to harden. This makes it harder (no pun intended) for the tire to conform to the road surface and really grip it. If the average winter temperature where you live is below 45 degrees, you should definitely consider switching to winter tires. They're made with compounds that stay flexible in cold weather. Even on completely dry roads, winter tires could help you stop faster than all season tires.

While all season tires do have grooves for mud and light snow, they won't have the same ice grip that winter tires do. A winter tire tread pattern has tons of little slits cut into the rubber, called sipes. These sipes increase the number of edges that contact the road, improving grip on icy roads.

Start winter off on the right foot (and tire).

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