Which of the following is a mechanical failure that proper vehicle maintenance aims to prevent?

Proper vehicle maintenance is crucial in preventing mechanical failures that can affect safety and performance. Flat tires are a direct result of mechanical wear and system integrity, often related to the maintenance practices of a vehicle. Regular checks on tire pressure, tread depth, and overall tire condition help identify issues before they lead to a flat tire.

In contrast, cracked windshields, while they can occur from impact or environmental factors, are not typically addressed through routine vehicle maintenance. Expired registration is related to compliance and legal status rather than the mechanical state of the vehicle. Lastly, broken seat belts, while critical for safety, often require specific inspection and replacement due to wear and use rather than ongoing maintenance in the same manner as tires. Thus, maintaining tires effectively helps in preventing the occurrence of flat tires as a mechanical failure.