Bicycle with asymmetric steerer tube
A bicycle steerer tube assembly having an oblong asymmetric cross section formed along a portion of the steerer tube. The asymmetric portion of the steerer tube has a first diameter that is generally aligned with an axis of rotation of the front wheel and a second diameter that is generally aligned with a plane of rotation of the front wheel. The first diameter is greater than the second diameter and provides lateral stiffness to the wheel assembly and the second diameter accommodates longitudinal impact absorption of the fork and wheel assembly.
1. A method of supporting a bicycle steerer tube comprising:
providing a steerer tube body that is shaped to cooperate with a head tube of a bicycle frame;
shaping a portion of the steerer tube body that is supported by the head tube to have a non-circular oblong cross section with a short axis aligned with a longitudinal axis of the bicycle frame and a long axis transverse to the short axis.
2. The method of claim 1 further comprising providing a bearing between the portion of the steerer tube body and the head tube, the bearing having an internal diameter that generally corresponds to the long axis of the non-circular oblong cross section at a location proximate the bearing.
3. The method of claim 1 further comprising tapering the steerer tube body from a first radially symmetric cross section to a second radially symmetric cross section with the non-circular oblong cross section positioned between the first and second radially symmetric cross sections.
4. The method of claim 3 further comprising providing a fork crown proximate the first radially symmetric cross section.
5. The method of claim 3 wherein the second radially symmetric cross section extends a greater length of the steerer tube body than the first radially symmetric cross section.
6. The method of claim 3 wherein the non-circular oblong portion of the steerer tube body extends a greater length of the steerer tube body than either of the first or second radially symmetric cross sections.
7. The method of claim 1 further comprising altering an eccentricity of the non-circular oblong cross section along a length of the steerer tube body.
8. A method of forming a bicycle steerer tube assembly comprising:
forming a steerer tube having a first end adapted to engage a fork crown and a second end adapted to engage a handlebar of a bicycle; and
forming an asymmetric cross section along the steerer tube between the first end and the second end so that a wider portion of the asymmetric cross section is aligned with a pair of fork cavities formed by the fork crown and a narrow portion of the asymmetric cross section is aligned with a longitudinal axis of a bicycle.
9. The method of claim 8 further comprising reducing a cross-sectional area of the steerer tube along a length of the steerer tube in a direction away from the fork crown.
10. The method of claim 9 further comprising reducing a width of the wider portion faster than the narrower portion along the length of the steerer tube.
11. The method of claim 8 further comprising forming a radially symmetric cross section between the asymmetric cross section and each of the first end and the second end of the steerer tube.
12. The method of claim 11 further comprising extending the radially symmetric cross section proximate the second end a greater a length of the steerer tube than the radially symmetric cross section proximate the first end.
13. The method of claim 8 further comprising integrally forming the steerer tube and the fork crown as a one-piece body from a carbon fiber material.
14. A method of forming a bicycle steerer assembly comprising:
forming a steerer tube and a fork crown as a one-piece body from a carbon fiber material;
forming the steerer tube with an oblong cross section that extends along a portion of a length of the steerer tube; and
forming a symmetric cross section of the steerer tube that offsets the oblong cross section of the steerer tube from the fork crown.
15. The method of claim 14 further comprising aligning a major axis of the oblong cross section with a pair of fork arms of the fork crown.
16. The method of claim 14 further comprising engaging a bearing with the symmetric cross section of the steerer tube so that the bearing is positioned proximate an end of the oblong section.