# Geometry of the bike frame.

#### The frame geometry.

Bicycles are different in sizes. These differences are related to the use of the bicycle and the length of the cyclist.
The size of the frame is largely determine for the final size of the bike. It is for the bicycle specialist therefore important to find a frame size that fits the size of the cyclist and the bicycle use.

The following sizes are of importance for the choice of the bicycle and the frame:
• The bracket height: = The distance between the axis of the bracket (bottom bracket) and the ground.
• The crank length: = The length of the cranks measured between the axis of the crankshaft and the center of the pedal shaft. By mounting a shorter or longer cranks is adapting the crank length to the leg length.
• The seat or saddle height: = The distance between the saddle and the pedal when the pedal parallel (in a line) is at the seat tube and is directed downward. This size can be adjusted by moving the seat post further or less far into the frame.
• The frame size or frame height: = The distance between the center of the bracket (bottom bracket) and the top of the saddle post lug. In almost all of the frames runs here the seat tube of the frame. In Italy, the frame size is measured from the top of the bracket. This saves about 2 cm. An Italian frame with 54 cm has a frame size of 56 cm. With some manufacturers of frames with sloping top tube, the frame size is the distance measured from the bracket (crank shaft), and the point of intersection of the seat tube and a horizontal line from the top of the steering head. There are also manufacturers that show the actual frame size for these frames.
• The seat angle: = In case of the frame is the seat angle, the line between the bracket and the saddle post lug makes with the ground and with the bicycle the angle of the bottom bracket with the center of the saddle. By sliding the seat forward or backward you can adjust the seating angle of the bike.
• The seatpost length: = the distance between the saddle and saddle post lug of the frame.
• The frame length or top tube length: = The distance between the head tube and the line between the bracket and the saddle post lug, measured horizontally. In the classic frame, this is the top tube.
• The steering distance: = The distance between the front of the saddle and the heart of the steerer tube. By changing a stem with shorter or longer front construction is this measure convertible. This size is also adjustible with a rotatable stem.
• The handlebar height: = The difference in height between the top of the saddle and handlebar stem. By turning the stem further or less far into the front fork is to adjust the steering wheel height.
• The front construction = The distance between the head tube and center of the steering tube, measured horizontally. Stems are available with different stem lengths.
• The handlebar stem length: = The distance between the upper head tube and heart of the steerer tube, measured parallel to the head tube.
• The steering angle: = the angle of the head tube with the ground.
• The jump: = The distance between the head tube and the axis of the front wheel, measured perpendicular to the head tube. Forks are available with various jumps. The jump affected the steering of the bike.
• The following course: = The distance between the point of contact of the wheel on the road surface and the tangent point of the center line through the head tube on the road. By mounting a fork with another following course is to change the trail.
• The wheelbase: = the distance between the axles of the front and rear wheel.
• The rear fork Length: = the distance between the center line of the bottom bracket and the rear axle.

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