Assess your riding style and skill level. Before deciding on a tire it is important to understand yourself as a rider. Ask yourself where you will be riding, what the terrain is like, how hard you will push yourself, where you want to go and how fast you want to get there. Fat and skinny tires each have their pros and cons.
Use skinny tires if you plan to ride on hard-packed trails or pavement. Skinny tires are very versatile for the leisurely rider or commuter. They offer a satisfactory amount of traction on dirt trails that are relatively free of debris. And because they have lower resistance than a fat tire, riders can maintain a more constant rate of speed and reduce fatigue. On the downside, skinny tires offer less protection for the wheels and have less traction when braking and cornering, especially on dirt.
Ride fat tires on challenging terrain and downhill courses. Fat tires, or tires that have more surface area, are perfect for riding trails that offer difficult obstacles such as rocks, trees, gravel and sand. Fat tires provide more control on the trail because they spread their traction better, have more shock absorption and protect the rims better than skinny tires do. Fat tires range in size from 1.5 inches to 3 inches, with the average being approximately 2.3 inches. There also is such a thing as a tire that is too fat; these tires are dangerous, especially on gravel, where the large surface area of the tire will react to the gravel as if the tire is on ball bearings.