system
Given the following post, respond as if you're commenting on Reddit:
human
Do different tire threads actually increase traction/range/fuel efficiency etc. or is it mainly a marketing trick?

We just got winter tires and I was just curious as to if they, along with "performance" and "off road" tires, really make a difference and if so how much?
gpt
It absolutely makes a difference. The tread geometry is one factor, another is the composition.

Treads are deformed under load, so the party of the tire on the ground is "squished". Depending on tread design, you have a different surface area and pattern that contacts the ground, which changes your traction - more significantly, it changes your traction under different conditons, too. Simple things like rolling direction, whether you're turning or not, all change the forces the tire must withstand, and how the tread is deformed. It if there's water in the road, you want the treads to force as much water into the channels as possible, so that as much tire as possible makes contact with the road itself. There's quite a lot of tread design in these optimizations, or for instance in increasing traction on snow or ice for similar reasons.

Now, winter vs. summer vs. all-season tires have another huge difference. The rubber itself. Rubber materials have different properties at different temperatures. As it gets cold, they become harder and less flexible. Conversely, they become softer at higher temperatures.

So, in the winter, a summer tire will be harder than is ideal, meaning it won't press onto the roadway as well, reducing your traction very significantly. In the summer, warm weather will mean winter tires are softer than ideal. The tire will make more contact than ideal, increasing the rolling friction that the car fights against (similar to a pumped wheel vs. a partially deflated one). If the rubber is too soft, it will be worth down faster also, so using winter tires in warm weather will also decrease their lifetime. In principle, tires become hard and brittle at low temperature, and could crack or chip. Realistically, you'd never see that side of the spectrum though.

Moral of the story - if you have Winters that get cold enough for snow, you need summer and winter tires in the respective seasons. If the whole year is fairly moderate, all seasons can be acceptable. If you're in the tropics, stuck with summer tires, and in the Arctic of course winter ones.