Exaggerated bottom bracket
The bottom bracket elevation is the difference between the height, measured from the ground, of the lowest point of the seat and the bottom bracket on a recumbent bike .
The greater this difference, the higher the pedals are in relation to the lowest point of the seat. If the bottom bracket is excessive, better aerodynamics are achieved because the rider has less surface area to attack the head wind ( frontal area ). On the other hand, a bottom bracket elevation means that the feet disturb the forward view.
The bottom bracket elevation determines the angle between the thigh and pelvic bones, which has an impact on ergonomics and performance. Many recumbent cyclists report that greater flexion in the hip joint - similar to a racing bike - enables greater physical performance.
Many low-flyers in particular have a strong crankcase elevation . With other short recumbent bikes , the bottom bracket elevation is usually low, while chair bikes usually have a negative bottom bracket elevation (bottom bracket lower than the seat).
literature
- Michael Gressmann, Franz Beck, Rüdiger Bellersheim: specialist knowledge of bicycle technology. 1st edition, Verlag Europa-Lehrmittel, Haan-Gruiten, 2006, ISBN 3-8085-2291-7