Mountain bikes principally depend on it’s frames design and construction. As mountain bike undertake a huge variety of differnt tasks and becuase of this, each type of activity generally requires a different frame type. So lets discuss different types of frames you can get:

Types of metals used in Bike Frame Cosntruction
A bike’s frame can be made from a variety of differing materials which can significantly affect the weight of the bike. Generally the heavier frames are steel while steel alloy frames are much ligher in weight, and are generally used in street riding, such as riding to and from work. In other words, they are generally meant for pavement or road riding. These steel-alloy frames tend to be much more brittle, and can bend or break if used in a demanding out door ride.Aluminum is generally used fir the lightest frames and are usually used in bikes meant for free riding and downhill biking. The frames tend to be more flexible and can put up with a lot of heady handling .

The size of the Frame
Frame size can have a big bearing on the usability of a bike, becuase bigger bikes are generally heavier and can be slight more unstable at slower speeds (higher centre of gravity), but can be great when going downhill. Whereas, smaller frames generally tend to be lighter and easier to handle on difficult dirt tracks.