Full-size spare tires, which are identical to the four tires on a vehicle, are increasingly rare on new vehicles, with only about 10% of new cars including them as of 2020, replaced by "donuts" or tire sealant kits. Discontinued due to the need to reduce vehicle weight for fuel efficiency, minimize production costs, and maximize cargo space, these spares provide full driving performance without limitations.

Definition and Purpose: A full-size spare tire is a fifth tire and wheel (often on a steel rim, even if the main wheels are alloy) that matches the size, performance, and functionality of the standard tires on the vehicle.

Benefits: It allows for normal driving speeds and distances after a flat, eliminates the need for immediate repair, and can be rotated into the vehicle's maintenance cycle, effectively extending the life of the set.

Disadvantages: They are heavy (adding 50-60 lbs), take up significant cargo space, and increase manufacturing costs.

Reasons for Discontinuation

Fuel Economy (CAFE Standards): To meet stricter regulations, automakers remove excess weight, such as the 50-60 pounds of a full-size tire and jack.

Cost Reduction: Removing the fifth tire and wheel saves manufacturers money.

Space Optimization: Eliminating the spare allows for deeper cargo holds, increased cabin space, or the installation of hybrid/electric batteries.

Improved Technology: Modern tires are more durable, and the rise of run-flat tires allows drivers to continue without an immediate change.

Consumer Behavior: Many drivers prefer calling roadside assistance over changing a tire themselves.