Size

• The traditional way of sizing a bike frame is by measuring from its lowest point to its highest point. This means that the measurement is taken from the bottom bracket to the top of the seat tube. The average size for a road bike ranges from 21 to 23 inches (53 to 58 centimeters), while the size of a typical mountain bike is 18 1/2 inches. Sizes vary depending on make and model, and certain frames are measured differently today, incorporating the length of the frame into the measurement.
  
  

Identification

• The bike frame looks like two triangles put together to form an odd-shaped diamond. The main triangle consists of a head tube, which the handlebar sticks out of, a top tube running between the handlebar, and the seat, a seat tube that runs from where the seat connects to just in front of the rear wheel. The down tube runs behind the front tire and connects at the bottom with the seat tube, where the gears and pedals attach. The rear triangle of the frame is smaller and is made up of the seat tube, the seat stay, and the chain stay. These last two tubes run to the middle of the rear wheel and have connections to the bike chain, the brakes and the gears.
  
  

Type

• There are different types of bike frames that are made for different types of bikes. These different frames are also made of different materials and sizes and even shapes. Frames on racing bikes, for example, are made of lighter materials and are more compact, while frames for touring bicycles, or those used to ride long distances, are longer than the average bike frames. More rare types of bike frames are seen on other bikes and have unique geometric features. These are found on Humbler bikes, recumbent bikes and others.
  
  

Effects

• Bicycle frames have different effects on the bike they are part of depending on the type of bike and the makeup of the frame. Racing bikes are meant to go fast and their frames have been designed for this. Many racing bikes have a steep seat tube, which takes away the comfort of riding the bike in exchange for putting the rider in a more aerodynamic position. Many racing bikes are also more compact and are almost always made of the lightest materials possible. Touring bikes are made for comfort and long rides, so their frames are less aerodynamic, bigger all around, and set the seat horizontal for comfort reasons. Mountain bikes feature suspensions in order to make a smooth ride over rough terrain, and their bike frames are made to give that effect, as well. Many mountain bike frames have a pivoting rear triangle that will move as the bike rides over rocks and debris.
  
  

Expert Insight

• Bike frames feature different materials that offer varied results while riding the bike. The materials used have different density, weight and stiffness, and all of these features affect the bike as a whole. Steel is one of the cheaper materials bike frames can be made of, and this lowers the price of the bike. Steel frames are strong and are used in some road bikes and many mountain bikes because they can really take a hit. Aluminum frames are generally lighter than steel frames, and they are not much more expensive to produce. While they are not as strong or dense as steel tubes, their weight and ease of construction have made them the most popular frame material. Titanium is used in top of the line bikes, but it is rare and very expensive and usually another material is better for a bike frame because of this. Carbon fiber bike frames are highly sought after because they resist corrosion and are very light. While expensive, their weight makes them very popular for racers. While other materials from plastic to bamboo are sometimes used to make bike frames, the materials here are the most common.