Bicycle frame

1. A bicycle frame comprising:

a head tube;

a bottom bracket adapted to support a crankset;

a seat tube extending upward from the bottom bracket; and

a tubular frame member coupled between the head tube and the seat tube and having a longitudinal axis, the tubular frame member including a concave section disposed on an underside of the frame member and spaced from the head tube without extending beyond a longitudinal midpoint of the tubular frame member, the concave section located closer to the head tube than the seat tube,

wherein, in cross-section taken through the concave section and across the longitudinal axis, the underside has a concave profile.

2. The bicycle frame of claim 1 , wherein the tubular frame member is a down tube coupled to the head tube and the bottom bracket, and wherein the concave section is located between the head tube and the bottom bracket.

3. The bicycle frame of claim 2 , wherein the concave section is spaced from the bottom bracket.

4. The bicycle frame of claim 1 , wherein the concave section is located closer to the head tube than to the bottom bracket.

5. The bicycle frame of claim 1 , wherein the tubular frame member defines a longitudinal axis and has a first length along the axis, and wherein the concave section extends along the longitudinal axis and has a second length that is at most 40 percent of the first length.

6. The bicycle frame of claim 1 , wherein the concave section has a central recess and a curved ridge at least partially surrounding the central recess to define a substantially oval-shaped depression in the tubular frame member.

7. The bicycle frame of claim 1 , wherein the concave section has a central recess and a curved ridge laterally disposed along the central recess, and wherein at a longitudinal center of the concave section, the tubular frame member has a width and the curved ridge has a radius of curvature that is at least 8 percent of the width.

8. The bicycle frame of claim 1 , wherein the concave section has a width and a length defining a ratio of width/length, and wherein the ratio is equal to or less than 0.25.

9. A bicycle frame comprising:

a head tube;

a bottom bracket adapted to support a crankset; and

a down tube coupled to the head tube and the bottom bracket, the down tube defining a longitudinal axis, the down tube including a concave section disposed on an underside of the down tube, the concave section spaced from the head tube and the bottom bracket and located closer to the head tube than the bottom bracket, the concave section having a central recess and a curved ridge disposed along and at least partially surrounding the central recess to define a substantially oval-shaped depression in the down tube.

10. The bicycle frame of claim 9 , wherein at a longitudinal center of the concave section, the down tube has a width and the curved ridge has a radius of curvature that is at least 8 percent of the width.

11. The bicycle frame of claim 9 , wherein the concave section is spaced from the head tube.

12. The bicycle frame of claim 9 , wherein the concave section has a width and a length defining a ratio of width/length, and wherein the ratio is equal to or less than 0.25.