Flat.

Part of being a private pilot is doing a thorough pre-flight inspection of the airplane before setting off on an adventure. This is especially important with rental aircraft and double important for those aircraft being used by primary students. The flight school requires that a student pay for damaged tires; the tire shown above has a flat spot. It’s still safe, but it will need to be replaced soon. I’m happy I discovered this before my flight so I don’t get blamed for the flat spot and end up paying for the tire. Take a photo and send it to the mechanic.

The flat spots usually result from pilots having their feet on the brakes with they land. I had a tire blow out on a landing years ago; it’s not a pleasant experience.