Depending on what style of mountain biking you want to focus on, there are many different kinds Cannondale MTB to choose from. Here are some points that will help you make your decision:
Cross country: the majority of mountain bikes will fit into that category, because this is by far the most common mountain bike. It can only be used for cross country - which means hills and mountains, but even back to work.
Riding a bike: this type of bike is for serious cyclists who like the ultimate adventure. They strongly depend on the strength of their components, such as rear and front suspension, gears, disc brakes, and indeed the frame. Most of the downhill bike riders will spend a lot of time and money to customize our bike.
Jump and slalom bikes: bikes incredibly strong, and are designed to not only jump and slalom courses, but also for street racing. Again, a very popular model for serious mountain bikers.
Trials Bikes: Trials riding is a sport of precision and requires a very high degree of skill. Again, similar to downhill riding, more advanced trials riders will design their own bikes rather than buy off the shelf.
As you can see there are a number Cannondale mountain bikes to choose from and your final choice will depend on your style. If you are really sure what style of bike is right for you then the best thing to do is to try some of the first before making a final decision.
