Chainring for a bicycle

1. A bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces, the chainring comprising:

a) a body having a mounting portion configured to be connected to a bicycle and a periphery, the body being rotatable about a drive axis when connected to the bicycle and defining a central plane that is orthogonal to the drive axis;

b) a plurality of first teeth spaced apart from each other around the periphery, extending radially outwardly from the periphery and configured to fit within the narrow link spaces in the drive chain;

c) a plurality of second teeth disposed alternatingly between adjacent ones of the first teeth around the periphery and configured to fit within the wide link spaces in the drive chain, each second tooth extending radially from a root adjacent the periphery to a tip that is spaced from the root by a tooth height and has a tip width in the axial direction, each second tooth having:

i. a first width that is greater than the tip width and is measured orthogonally to the radial direction in a first plane that is disposed between about 40% and about 60% of the tooth height and; and

ii. a second width that is greater than the first width and is measured orthogonally to the radial direction in a second plane that is disposed radially between the first plane and the root; and

iii. a first transition portion on a first side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in an edge direction that is substantially parallel to the central plane and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the first transition portion.

2. The bicycle chainring of claim 1 , wherein each second tooth further comprises a second transition portion on an opposing second side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in the edge direction and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the second transition portion.

3. The bicycle chainring of claim 1 , wherein the first plane is disposed at about 50% of the tooth height.

4. The bicycle chainring of claim 1 , wherein the first width is less than about 80% of a width of the wide link spaces.

5. The bicycle chainring of claim 1 , wherein the second width is at least 110% of the first width.

6. The bicycle chainring of claim 1 , wherein each second tooth is configured so that the second width is between about 95% and about 105% of a width of the wide link spaces.

7. The bicycle chainring of claim 1 , wherein the second plane is positioned so that the second plane is disposed radially below and does not intersect opposing active link surface faces of the drive chain that bound the wide link spaces when the second tooth is fully received within a corresponding one of the wide link spaces.

8. The bicycle chainring of claim 1 , wherein each second tooth generally widens from the tip to the second plane.

9. The bicycle chainring of claim 1 , wherein the first transition portion comprises a first transition surface that extends continuously between the first edge and the first plane.

10. The bicycle chainring of claim 9 , wherein the first transition surface extends continuously between the first edge and the second plane.

11. The bicycle chainring of claim 10 , wherein the first transition surface comprises a first chamfer surface and is substantially planar and inclined relative to the central plane.

12. The bicycle chainring of claim 9 , wherein the first side of each second tooth further comprises a first edge surface intersecting with the second edge of the first transition portion and extending away from the first transition portion and parallel to the central plane.

13. A bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces, the chainring comprising:

a) a body having a mounting portion configured to be connected to a bicycle and a periphery, the body being rotatable about a drive axis when connected to the bicycle;

b) a plurality of first teeth spaced apart from each other around the periphery, extending radially outwardly from the periphery and configured to fit within the narrow link spaces in the drive chain;

c) a plurality of second teeth disposed alternatingly between adjacent ones of the first teeth around the periphery and configured to fit within the wide link spaces in the drive chain, each second tooth extending radially from a root adjacent the periphery to a tip that is spaced from the root by a tooth height and has a tip width in the axial direction, each second tooth having:

i. a first width measured orthogonally to the radial direction in a first plane that is disposed between about 40% and about 60% of the tooth height and that is greater than the tip width and is less than 80% of a link width of the wide link spaces; and

ii. a second width measured orthogonally to the radial direction in a second plane that is disposed radially between the first plane and the root and that is at least 95% of the link width.

14. The bicycle chainring of claim 13 , wherein each second tooth further comprises a first transition portion on a first side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in an edge direction that is substantially parallel to the central plane and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the first transition portion and wherein each second tooth further comprises a second transition portion on an opposing second side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in the edge direction and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the second transition portion.

15. The bicycle chainring of claim 13 , wherein the second width is at least 110% of the first width.

16. The bicycle chainring of claim 13 , wherein each second tooth is configured so that the second width is between about 95% and about 105% of a width of the wide link spaces.

17. The bicycle chainring of claim 14 , wherein the first transition portion comprises a first chamfer surface that is substantially planar and inclined relative to the central plane and that extends continuously between the tip and the second plane.

18. A bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces, the chainring comprising:

a) a body having a mounting portion configured to be connected to a bicycle and a periphery, the body being rotatable about a drive axis when connected to the bicycle;

b) a plurality of first teeth spaced apart from each other around the periphery, extending radially outwardly from the periphery and configured to fit within the narrow link spaces in the drive chain;

c) a plurality of second teeth disposed alternatingly between adjacent ones of the first teeth around the periphery and configured to fit within the wide link spaces in the drive chain, each second tooth extending radially from a root adjacent the periphery to a tip that is spaced from the root by a tooth height and has a tip width in the axial direction, each second tooth having:

i. a first width measured orthogonally to the radial direction in a first plane that is disposed at about 50% of the tooth height and that is greater than the tip width; and

ii. a second width measured orthogonally to the radial direction in a second plane that is disposed radially between the first plane and the root and is disposed radially below and does not intersect opposing active link surface faces of the drive chain that bound the wide link spaces when the second tooth is fully received within a respective one of the wide link spaces, the second width being greater than the first width;

wherein each second tooth widens continuously from the tip to the second plane.

19. The bicycle chainring of claim 18 , a first transition portion on a first side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in an edge direction that is substantially parallel to the central plane and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the first transition portion.

20. The bicycle chainring of claim 19 , further a second transition portion on an opposing second side of the second tooth that is at least partially bounded by and extends between a first edge that is at the tip and extends in the edge direction and a second edge that is disposed at the second plane and extends in the edge direction, the first and second planes intersecting the second transition portion.