Jason Fenske from Engineering Explained is here to tell you all about what happens as your tires wear down. While you think it's a simple reduction in grip, there's a whole lot more to process. In fact, certain tires can see an increase in grip as the tire wears down. Confused? You won't be for long.
One of the most important features for a tire is how much grip it provides. That grip is surmised through analysis of three areas of the tire; construction, compound, and the tire pattern itself. It's the construction of a tire that determines its shape with respect to the height of the tire and its width. And it's here where the contact patch is formed.
When talking about the stickiness of a given tire, you're describing its compound. A low-rolling resistance tire and a high-performance track tire will have very different compound compositions. The right compound for a given tire returns tremendous grip levels. Finally, the tread itself figures into the grip equation by performing different jobs depending on the road conditions at hand. A tire that's good in wet conditions uses its tread to wick away water as the car runs down the road, while a high-performance tire will have far less of a tread pattern as the goal is to maximize the amount of rubber touching the ground.
For wet weather, a worn down tire will have less tread on it and thus its water-wicking properties will be reduced. You'll soon discover that you have a lower cornering threshold and diminished braking capabilities revealed as longer stopping distances. On the flip side, a worn performance tire that has reduced tread will actually transmit increased dry weather performance for some time. Like a slick racing tire, you are working with an increased contact patch that delivers more grip.
Of course, that's not going to last forever and the tire will eventually begin to break down. So even a worn performance tire driven in dry conditions will eventually begin behaving poorly.
Keep an eye on your tires and know what sort of conditions in which you'll be operating. The right tire on the right vehicle, and in the right weather, can yield nearly magical results. But remember that the opposite is true as well.