Generally speaking, there are many different kinds of mountain bicycles, as there are many ways to classify them. However, for simplicity, one easy way to classify mountain bicycles is by their wheel, or tire size. Later, we will see that there is far more that goes into it that that, but for now, the 3 main categories of mountain bicycles, based on wheel or tire size, with one exception are:
26er Mountain Bikes use 26″ wheels. Traditionally, this is the most common mountain bike size. All vintage mountain bikes have 26″ tires. A mountain bike could be considered vintage if it is dated between 1978, when the modern mountain bike was invented, all up to the early 1990s.
29er Mountain Bikes use 26″ wheels – This was the latest and greatest mountain bike trend until around 2007 until around 2012, when 27.5″ mountain bikes started to become popular.
27.5″ or 650b Mountain Bikes use 27.5″ wheels. This is a more recent idea, and a bike size that many saw as an improvement over the 29er, because these types of bikes generally tend to be more manurevable than 29ers, while being better than 26ers at rolling over obstacles.
Fat Tire Mountain Bikes use very wide wheels. These bikes are in a class of their own, because they can “float” over loose snow and mud, a feat that most of the three other types of mountain bikes cannot do. Now, most fat tire bikes could be classified as 26ers, as most use 26″ wheels. However, because they use very wide tires that fit on very wide rims, that are not interchangeable with other types of 26er mountain bikes, they really deserve to be classified as their own type of bike.
Its important to note, here, that tire size is determined by wheel size. In other words, the tire size for a specific kind of bike is based on the wheel size, or diameter of the wheel. Of course, wheels of one particular size of bicycle can be different widths, and be different sizes when you are referring to how tall the sidewall and tread of the tire is, so to speak, but the inner diameter of the tire is always the same size as the diameter of the wheel it is seated in.
Full Suspension Frames Also known as dual suspension mountain bikes, these bikes have both a front and rear suspension. Originally, all full suspension mountain bikes were 26ers, but things have changed, and you now have full suspension bikes in all wheel sizes, including fat tire bikes.
Hardtail Frames Traditionally, all bikes, except dual suspension bikes, are hardtails. Early mountain bikes had rigid forks, which is why some hardtail bikes are also known as front suspension bikes, because they have a suspension fork on the front of the bike. However, hardtails so not have a suspension in the rear tainangle of the bike.
In addition, mountain bikes are often defined by their frame material, assuming that frame material isn’t aluminum, which most mountain bikes are made from. For example, steel and carbon fiber are popular materials which many mountain bikes are made from. Steel mountain bikes tend to flex more than aluminum bikes, and therefore tend to be a little more comfortable to ride. Carbon mountain bikes have a similar ride feel to steel, but typically, they are going to be lighter weight.
Style of Riding
In addition, the style of riding a mountain bike is meant for can determine its category. For example, there are mountain bikes designed for trail riding, or cross country. There are downhill mountain bikes that are designed to go very fast down hill. These bikes, of course, are not the greatest climbers. There are also mountain bikes designed for enduro and freeriding.
Sex of Rider
One more popular type of mountain bicycle that is gaining in popularity are women’s mountain bikes, which have special frame geometry designed specifically for women.
Finally, one more category that is used to classify mountain bicycles is single speed or fixed gear, which means just one gear. While all fixed geared bikes are single speed bikes, the difference is that fixed geared bikes do not have a freewheel (unless, of course, they come with a flip flop hub), meaning the crankset will always turn the same direction with the tires. If you aren’t careful with a fixed geared bike, you can easily damage your knees if your pedaling cadence is at a different pace than the tires are spinning, which can also send you flying over the handlebars!