Final answer:
A worn brake drum can cause brakes to pull or grab, heat up quickly, and potentially split or crack, all of which can compromise vehicle safety.
Step-by-step explanation:
When a brake drum is worn too thin, the brakes may pull or grab, leading to uneven braking performance. This can be dangerous as it may cause the vehicle to veer to one side unexpectedly during braking. Moreover, a thin drum may heat up more quickly due to less mass to absorb and dissipate the heat generated by the friction between the brake shoes and drum. This excessive heat can lead to brake fade, reducing the effectiveness of the brakes. Lastly, there's a significant risk that the drum will split or crack due to the high stresses and temperatures it encounters, especially if it is beyond the manufacturer's minimum thickness specification. This can lead to brake failure and is a critical safety concern.