What should you check regularly if your car has a spare wheel carried outside the body of the car?

You answered correctly by choosing to regularly check the double safeguard and the tyre pressure of an externally carried spare wheel. According to German traffic rules, the double safeguard ensures that the spare wheel is securely fastened and does not pose a risk of detaching while driving. Checking tyre pressure is essential because a spare wheel stored outside the car can lose pressure over time, potentially making it unsafe to use in an emergency. The rolling resistance is not a primary concern for a spare wheel carried externally, so it is not necessary to check it regularly. Keeping these checks in mind helps ensure safety and readiness in case you need to use the spare wheel.