Eventually the plasticisers will break down and the tire will start falling apart leaving plastic dust every where; best for that to happen in a landfill imo.

Tires can't really be recycled and usually end up being burned for energy, releasing toxins and CO^2^ into the atmosphere, much like how most plastics aren't actually recycled either. In my province (BC), they have recycling programs but those also release toxins, just at a slower rate while in the close proximity of children (rubber surfaces in playgrounds).

https://www.sciencedirect.com/science/article/pii/S2405844025002890