Front brakes, including the brake shoes in drum brake systems, are responsible for the majority of the motorcycle's stopping power, typically 70% or more. This is because when braking, weight shifts forward, increasing the front wheel's grip and making the front brakes more effective. 

Worn-out brake shoes can lead to increased stopping distances, unusual noises (squealing or creaking), and vibrations during braking. It's essential to inspect brake shoes regularly and replace them to ensure optimal braking performance and safety.