Mountain bike frames are the main structure of a mountain bike, providing support and stability. They are typically made from materials like aluminum, carbon fiber, or steel, each offering different benefits in terms of weight, strength, and cost. The design of the frame affects the bike's handling, comfort, and performance on various terrains. Frames come in different styles, such as hardtail and full-suspension, catering to different riding preferences. A hardtail frame has a front suspension but no rear suspension, making it lighter and more efficient on smooth trails. In contrast, a full-suspension frame includes both front and rear suspension, providing better shock absorption on rough terrain.