Patent Publication Number: US-2022228657-A1

Title: Chainring for a bicycle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/697,720 filed Nov. 17, 2019 and entitled “Chainring for a Bicycle”, which claims the benefit under 35 U.S.C. § 138(e) of U.S. provisional patent application No. 62/772,209 filed on Nov. 28, 2018 and U.S. provisional patent application No. 62/846,854 filed on May 13, 2019, each of which is hereby incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to bicycle chainrings, and more specifically, to front chainrings for use with a bicycle crankset and bicycle chain having alternating narrow and wide link spacings. 
     BACKGROUND 
     U.S. Pat. No. 9,731,790 describes a bicycle chainring includes a plurality of teeth extending from a periphery of the chainring wherein roots of the plurality of teeth are disposed adjacent the periphery of the chainring. The plurality of teeth include a first group of teeth and a second group of teeth, each of the first group of teeth wider than each of the second group of teeth, and at least some of the second group of teeth arranged alternatingly and adjacently between the first group of teeth, wherein the center of a top land of at least some of the first and second groups of teeth are offset from a plane in a direction toward one of the inboard and outboard sides of the chainring. 
     U.S. Pat. No. 4,174,642 describes a chain drive that includes a sprocket rotatable in a plane and comprising an even number of wide and narrow tapered teeth and a flexible chain comprising successive links having alternate wide and narrow tooth-engaging link openings, with tooth width and link-opening width being measured in a direction transverse to the plane of sprocket rotation. The arrangement ensures proper registration and engagement of the link opening of each oncoming link with a tooth of appropriate width despite displacement of the oncoming chain flight from the plane of sprocket rotation and thereby prevents disengagement of a loose chain from the sprocket or breakage of a tight chain by the sprocket. 
     U.S. Pat. No. 9,731,790 describes a bicycle chainring that includes a plurality of teeth extending from a periphery of the chainring wherein roots of the plurality of teeth are disposed adjacent the periphery of the chainring. The plurality of teeth include a first group of teeth and a second group of teeth, each of the first group of teeth wider than each of the second group of teeth, and at least some of the second group of teeth arranged alternatingly and adjacently between the first group of teeth, wherein the center of a top land of at least some of the first and second groups of teeth are offset from a plane in a direction toward one of the inboard and outboard sides of the chainring. 
     SUMMARY 
     Modern bicycles typically use one front chainring and may employ various devices to help stop chain derailment including chain guides and tensioners. 
     Chain retention is especially important in off-road cycling where the chain moves considerably up/down and side-to-side when traveling on rough terrain. 
     Avoiding chain derailment in off-road cycling is therefore a concern from a performance standpoint as inopportune derailment could cause a crash or cause a bicycle rider to lose a race. One solution to this problem has been to create chainrings that have alternating wide and narrow teeth so that the teeth a more closely matched in width with the distance between alternating wide and narrow link spacing of a typical bicycle chain. It has generally been thought that configuring the teeth to fill at least 80% of the width of the respective link space can help reduce misalignment, and that both the skinny and wide teeth should have a relatively short, tapered section to help urge the chain quickly into alignment with the chainring. 
     For example, U.S. Pat. No. 9,291,250 discloses an alternating wide narrow tooth arrangement wherein a maximum axial width of the wide teeth is provided at a location that is about halfway between a root circle and a top land of the wide group of teeth (e.g. about 50% of the distance from root to top land) so that the tooth fills at least 80 percent of an axial distance defined by the outer link spaces at this location. Similarly, U.S. Pat. No. 4,174,642 illustrates an alternating wide narrow tooth arrangement wherein a maximum axial width at toward the midpoint of the tooth height and fills about 85 percent of an axial distance defined by the outer link spaces. This patent also shows an outer link retaining face ( 53 ) that is only approximately 40 percent of the length of the wide tooth at a position close to the tooth root. In these designs the wide teeth widen from their tip to about their midpoint, at which point they have reached their maximum width and then maintain substantially the same width until reaching their root. 
     It has been noticed by the inventor that filling 80 percent of the outer link space this close to the tooth tip can cause a relatively abrupt realignment or the chain, which can be undesirable. For example, such an abrupt realignment may contribute to relatively higherwear on the chainring and loss of pedaling efficiency due to high outer chain link side loads and friction. These known chainrings also typically have multiple faces or surfaces that will contact and engage with the link plates of the chain as it settles radially onto the tooth. When acting to re-align a misaligned chain, the link plates of the chain will bear against and slide along these different faces of the chainring teeth, as well as grinding against the transitions/edges between the teeth bearing surfaces. This engagement produces friction as the chain is brought back into alignment which can contribute to relatively high wear at the transitions between adjacent tooth bearing tooth faces. Over time, this can wear down the chain-engaging portions of the wide teeth relatively quickly, which can result in the teeth becoming less effective at re-aligning the chain. 
     It was also noticed that because of the relatively abrupt widening of the wide teeth that the surfaces that engage and contact the link plates of the chain are relatively small and are inclined at relatively steep angles relative to a central plane of the chainring. In this arrangement, the forces transmitted by the generally vertical and parallel chain link faces will tend to be applied to these relatively small tooth contact surfaces, which can help contribute to the accelerated wear of such surfaces as the misaligned chain is brought back into alignment resulting in high wear during transition from face to face. 
     Therefore, despite the existence of some examples of a chainring that has alternating narrow and wide teeth there remains a need for an improved version of a chain ring that may help to address some of the shortcomings noted herein, and optionally may include a new wide tooth design. 
     The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the entirety of the wide tooth inner and outer link engaging faces are formed as a single plane or a constant radius curve and converge towards to tooth tip. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein a maximum axial width about halfway between a root circle and a top land of the wide group of teeth fills less than 80 percent of an axial distance defined by the outer link spaces and wherein a maximum axial width adjacent the root is at least 90 percent of an axial distance defined by the outer link spaces 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide tooth inner and outer link engaging faces also define the tooth tip chamfer on the narrow teeth. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide tooth top land and the narrow tooth top land are the same width. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide and narrow tooth tips are centered between planes defined by the inner and outer faces of the narrow teeth. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide and narrow tooth tips are centered between planes defined by the inner and outer faces of the wide teeth. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide and narrow tooth tips are centered between planes defined by the inner and outer faces of the chainring at a location adjacent the outer periphery. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide and narrow tooth tips are offset closer to a plane defined by the inner face of the chainring at a location adjacent the outer periphery than to a plane defined by a mounting face adjacent to the chainring axis. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the wide teeth are symmetric about a plane that is parallel to the chainring rotation axis and bisects the wide tooth top land. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the narrow teeth are symmetric about a plane that is parallel to the chainring rotation axis and bisects the narrow tooth top land. 
     One aspect of the teachings described herein provides an alternating wide narrow bicycle chainring wherein the width directly adjacent to and below the root periphery is narrower than both the wide and narrow teeth. 
     The teachings described herein may, in one broad aspect, relate to a bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces. That chainring may include a) a body having a mounting portion that may be connected to a bicycle and a periphery. The body may be rotatable about a drive axis when connected to the bicycle and may define a central plane that is orthogonal to the drive axis. A plurality of first teeth may be spaced apart from each other around the periphery and may extend radially outwardly from the periphery and may be configured to fit within the narrow link spaces in the drive chain. A plurality of second teeth may be disposed alternatingly between adjacent ones of the first teeth around the periphery and may be configured to fit within the wide link spaces in the drive chain. Each second tooth may extend radially from a root adjacent the periphery to a tip that is spaced from the root by a tooth height and may have a tip width in the axial direction. Each second tooth may have 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 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. A first transition portion may be provided on a first side of the second tooth and may be at least partially bounded by and extend 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 may intersect the first transition portion. 
     Other aspects of the teachings described herein, which may be used in combination with any other aspect, including the broad aspect listed above, may include that each second tooth of the bicycle chain ring 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. 
     The first plane may be disposed at about 50% of the tooth height. 
     The first width may be less than about 80% of a width of the wide link spaces. 
     The second width may be at least 110% of the first width. 
     The second width may be at least about 120% and/or about 125% of the first width. 
     Each second tooth may be configured so that the second width is between about 95% and about 105% of a width of the wide link spaces. 
     The second plane may be disposed between about 10% and about 30% and/or about 40% of the tooth height and may preferably be disposed at about 25% of the tooth height. 
     The second plane may be positioned so that the second plane is disposed radially below or inwardly and does not intersect opposing active link surfaces 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. 
     Each second tooth may generally widen from the tip to the second plane. 
     The first transition portion of the bicycle chainring may comprise a first transition surface that extends continuously between the first edge and the first plane. 
     The first transition surface may extend continuously between the first edge and the second plane. 
     The first transition surface may have a first chamfer surface and may be substantially planar and inclined relative to the central plane. 
     The first transition surface may have an arcuate, convex first fillet surface. 
     The first fillet surface may have a constant radius of curvature. 
     The first side of each second tooth may further comprise 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. 
     The first transition surface may have a transition height in the radial direction and the inboard edge surface has an edge height in the radial direction that is between about 5% and about 15% of the transition height. 
     The second width may define the widest extent of the second tooth. 
     Each second tooth may comprise a top land surface that extends axially and defines the tip width. 
     The first width may be less than about 3.0 mm and the second width may be between about 3.4 and about 4.2 mm 
     Each second tooth may include a third width measured orthogonally to the radial direction in a third plane that is disposed between the second plane and the root and that may be less than the second width. 
     The third width may be less than the first width. 
     The third width may be the same as a root width of the roots of the first teeth. 
     The teachings described herein may, in another broad aspect, relate to a bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces. 
     The chain ring may include a body having a mounting portion configured to be connected to a bicycle and a periphery. The body may be rotatable about a drive axis when connected to the bicycle. A plurality of first teeth spaced may be apart from each other around the periphery, extend radially outwardly from the periphery, and may be configured to fit within the narrow link spaces in the drive chain. A plurality of second teeth may be disposed alternatingly between adjacent ones of the first teeth around the periphery and may be configured to fit within the wide link spaces in the drive chain. Each second tooth may extend 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 may have 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 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. 
     Other aspects of the teaching described herein, which may be used in combination with any other aspect, including the broad aspect listed above, may include that each second tooth has 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 may intersect the first transition portion. 
     Each second tooth may have 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 may intersect the second transition portion. 
     The first plane may be disposed at about 50% of the tooth height. 
     The second width may be at least 110% of the first width. 
     The second width may be at least about 120% and/or about 125% of the first width. 
     Each second tooth may be configured so that the second width is between about 95% and about 105% of a width of the wide link spaces. 
     The second plane may be disposed between about 10% and about 30% of the tooth height and may preferably be disposed at about 25% of the tooth height. 
     The second plane may be positioned so that the second plane is disposed radially below and does not intersect opposing active link 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. 
     Each second tooth may generally widen from the tip to the second plane. 
     The first transition portion may include a first transition surface that extends continuously between the tip and the first plane. 
     The first transition surface may extend continuously between the tip and the second plane. 
     The first transition surface may include a first chamfer surface and may be substantially planar and inclined relative to the central plane. 
     The first transition surface may include an arcuate, convex first fillet surface. 
     The first fillet surface may include a constant radius of curvature. 
     Each second tooth may include an inboard edge surface intersecting the second edge of the first transition surface at the second plane and extending parallel to the radial direction from the second plane. 
     The first transition surface may have a transition height in the radial direction and the inboard edge surface may have an edge height in the radial direction that is between about 5% and about 15% of the transition height. 
     The second width may define the widest extent of the second tooth. 
     Each second tooth may comprise a top land surface that extends axially and defines the tip width. 
     The first width may be less than about 3.0 mm and the second width may be between about 3.4 and about 4.2 mm. 
     Each second tooth may have a third width measured orthogonally to the radial direction in a third plane that is disposed between the second plane and the root and that may be less than the second width. 
     The third width may be less than the first width. 
     The third width may be the same as a root width of the roots of the first teeth. 
     The teachings described herein may, in one broad aspect, relate to a bicycle chainring for engagement with a drive chain having alternating narrow link spaces and wide link spaces. The chainring may include a body having a mounting portion configured to be connected to a bicycle and a periphery. The body may be rotatable about a drive axis when connected to the bicycle. A plurality of first teeth may be spaced apart from each other around the periphery, extend radially outwardly from the periphery, and may be configured to fit within the narrow link spaces in the drive chain. A plurality of second teeth may be disposed alternatingly between adjacent ones of the first teeth around the periphery and may be configured to fit within the wide link spaces in the drive chain. Each second tooth may extend radially from a root adjacent the periphery to a tip that is spaced from the root by a tooth height and may have a tip width in the axial direction. Each second tooth may have 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 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 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 may be greater than the first width. Each second tooth may widen continuously from the tip to the second plane. 
     Other aspects of the teachings described herein, which may be used in combination with any other aspect, including the broad aspect listed above, may include 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. 
     There may further be 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a portion of one example of a bicycle drive chain; 
         FIG. 2  is a top view of the bicycle drive chain of  FIG. 1 ; 
         FIG. 3  is a lower perspective view of the bicycle drive chain of  FIG. 1 ; 
         FIG. 4  is a perspective view of one example of a chainring; 
         FIG. 5  is an enlarged view of a portion of the chainring of  FIG. 4 ; 
         FIG. 6  is a side view of the chainring of  FIG. 4 ; 
         FIG. 7  is an enlarged view of a portion of  FIG. 6 ; 
         FIG. 8  is a front view of the chainring of  FIG. 4 ; 
         FIG. 9  is an enlarged view of a portion of  FIG. 8 ; 
         FIG. 10  is a side view of the chainring of  FIG. 4  engage with a drive chain; 
         FIG. 11  is a cross-sectional view of the chainring and chain of  FIG. 10 , taken along line A-A; 
         FIG. 12  is a schematic representation of a cross-sectional view of a portion of the chainring of  FIG. 4  showing the drive chain partially engaged; 
         FIG. 13  is a schematic representation of a cross-sectional view of a portion of the chainring of  FIG. 4  showing the drive chain engaged. 
         FIG. 14  is a perspective view of another example of a chainring; 
         FIG. 15  is an enlarged view of a portion of the chainring of  FIG. 14 ; 
         FIG. 16  is a side view of the chainring of  FIG. 14 ; 
         FIG. 17  is an enlarged view of a portion of  FIG. 16 ; 
         FIG. 18  is a front view of the chainring of  FIG. 14 ; 
         FIG. 19  is an enlarged view of a portion of  FIG. 18 ; 
         FIG. 20  is a side view of the chainring of  FIG. 4  engage with a drive chain; 
         FIG. 21  is a cross-sectional view of the chainring and chain of  FIG. 10 , taken along line B-B; 
         FIG. 22  is a schematic representation of a cross-sectional view of a portion of the chainring of  FIG. 14  showing the drive chain partially engaged; 
         FIG. 23  is a schematic representation of a cross-sectional view of a portion of the chainring of  FIG. 14  showing the drive chain engaged; 
         FIG. 24  is a cross-sectional view of another example of a wide tooth for a chainring; 
         FIG. 25  is a cross-sectional view of another example of a wide tooth for a chainring; 
         FIG. 26  is a cross-sectional view of another example of a wide tooth for a chainring; and 
         FIG. 27  is side view of a chain seated on the chainring or  FIG. 4  with portions of the chain shown in phantom lines. 
     
    
    
     DETAILED DESCRIPTION 
     Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim, or dedicate to the public any such invention by its disclosure in this document. 
     Referring to  FIGS. 1 to 3 , one example of a drive chain  10  as contemplated for engagement with a bicycle chainring is shown to help illustrate some of the features of the chainrings described herein. This example of a drive chain is intended to be illustrative only, and in this example the drive chain  10  includes a number of outer link pairs  20 , inner link pairs  30 , pins  40  and rollers  50 . Other chain configurations may be used on a given bicycle and may be generally compatible with the examples of the chainrings described herein. 
     In this example, the outer link set  20  includes an outboard link  22  and an inboard link  42  that bound a wide link space  48  that can receive a tooth from a chainring. The distance between these links  22  and  42  (in a direction that is substantially orthogonal to the direction in which the chain moves) defines a wide link width  60 . In this example, the outboard link  22  and inboard link  42  have respective inner faces  44  and  24  as well as inner lead-in chamfers  46  and  26 . 
     Similarly, the inner link set  30  includes an outboard link  32  and an inboard link  52  that bound and a narrow link space  58  that can receive a tooth from a chainring. The distance between these links  32  and  52  (in a direction that is substantially orthogonal to the direction in which the chain moves) defines a narrow link width  62 . Outboard link  32  and inboard link  52  also include respective inner faces  54  and  34  as well as inner lead-in chamfers  56  and  36 . The inner faces of the chain links, such as faces  24  and  44 , and  34  and  54  can also be described as the active link faces of the chain as they are the faces that will tend to come into contact with the teeth on a corresponding chainring, and that may tend to bear against the chainring teeth when the chain is subjected to lateral forces and/or has become slightly misaligned. 
     In this description, references to inboard and outboard are used with reference to the usual position and orientation of the chain and/or chainring relative to the frame of a bicycle to which they are attached. Unless specified, objects that are generally symmetrical may be oriented relative to the bicycle frame in two different orientations and the identification of the features as either inboard or outboard is for ease of description and is not a restriction on how the object may ultimately be mounted or used. That is, a link that is described as an outboard link in  FIG. 2  may in fact become an inboard link when the chain is mounted to a bicycle in a different orientation, without materially altering how the chainring and chain engage with each other. 
       FIGS. 4-9  illustrate one example of a chainring  100  that can be attached to a bicycle crankset (not shown) and can be used to engage and drive the chain  10 . When mounted to the bicycle and the crankset is pedaled the chainring  100  is configured so that it will rotate in a rotation direction  102  (shown as clockwise in  FIG. 4 , but which could also be counter clockwise) about a rotation axis  104 . 
     In this example, the chainring  100  includes body  110  and a mounting portion  112  that is configured to be connected to a bicycle. The body surrounds and is rotatable about the rotation axis  104  and helps define a plane D ( FIG. 9 ) that is shown as being in the middle of the body  110  in the axial direction (i.e. parallel to rotation axis  104 ). The plane D is, in this example, substantially orthogonal or normal to and intersected by the rotation axis  104  and substantially bisects the body  110  in the axial direction. The thickness of portions of the chainring  100  when measured in a direction parallel to the rotation axis  104  is described as the width of such portions herein. When the chain  10  is seated on the chainring  100  ( FIG. 10 ) the link widths  60  and  62  are substantially parallel to the width direction of the chainring. A radial direction is understood to mean the direction extending outwardly from the rotation axis  104 , as shown using lines  108  in  FIG. 6 . For the purposes of discussion, the chainring  100  is described has having an outboard chainring face  114   a  and an opposing inboard chainring face  114   b  but it is understood that this orientation could be reversed if the chainring is connect to a bicycle in a different orientation. 
     Optionally, the mounting portion  112  may be of any configuration that is compatible with a bicycle crank set and may have different mounting hardware and configurations as desired. In this example, the mounting portion  112  includes a plurality of spaced apart mounting apertures  105   a - 105   d  that are sized to receive complimentary mounting bolts or other such fasteners. In other examples the mounting portion  112  may have a different configuration. 
     The chainring  100  also includes a periphery portion that surrounds the rotation axis  104 . The periphery portion in the illustrated example includes an outer or root periphery region  116  and an inner periphery region  170  that is radially in inboard from the periphery region  116 . In this example, the mounting portion  112  extends from the inner periphery region  170  and a plurality of teeth extend generally radially outwardly from the outer periphery region  116 , including a plurality of wide teeth  120  arranged in an alternating manner with a plurality of relatively narrow teeth  130 . In this example, the narrow teeth  130  all have substantially the same shape as each other, as do the wide teeth  120 . In other examples, some of the teeth on the chainring  100  may have a different configuration while the chainring  100  could still be understood to include a plurality of wide and narrow teeth  120  and  130 . 
     In this example, the narrow teeth  130  extend from respective roots  122  that are proximate the body  110  to respective tips  124  that are spaced apart from the roots  122  by a tooth height  126 . The wide teeth  120  also extend from respective roots  128  proximate the body  110  to respective tips  132  that are spaced from the roots  128  by the wide tooth height  134 . In the illustrated example the heights  126  and  134  are substantially equal, but in other examples may differ. Also, in this example the roots  122  and  128  of all of both types of teeth  120  and  130  lie along a common root groove  136  that is formed on the body  110  such that the roots  122  and  128  have substantially the same root width in the axial direction, one example of which is shown as root width  138  in  FIG. 12 . 
     Referring also to  FIG. 11 , the narrow teeth  130  are spaced apart from each other around the periphery  116  and are configured to fit within the narrow link spaces  58  in the drive chain  10 , having a maximum width  140  that is less than the narrow link width  62 . Also shown in  FIG. 11 , the wide teeth  120  are configured to fit within the wide link spaces  48  in the drive chain  10 , such that the width  142  of the wide teeth  120 , taken at the location of the section line A-A (e.g. in plane A of in  FIG. 13 ), is less than the wide link width  60 . 
     Referring again to  FIGS. 5 and 7 , the narrow teeth  130  in this example include drive faces  144  for driving a roller  50 , an inboard chamfer surface  146   a , an outboard chamfer surface  146   b  that converge toward a top land surface  148  and that help provide clearance when the tooth  130  is being inserted into the narrow chain space  58  and inboard and outboard side faces  150   a  and  150   b  that are generally radially oriented (i.e. generally parallel to plane D). The narrow teeth  130  can have a respective tip width  149  and a maximum width  151  ( FIG. 9 ) that can be configured to fit within the narrow chain space  58 . 
     Referring also to  FIGS. 11-13 , in this example, the wide teeth  120  include respective drive faces  152  for driving adjacent rollers  50  when in use and have a generally radially outwardly facing top land face  154  at is located at the tip  132  and defines a tip width  156  ( FIG. 12 ). In this example, the tip width  156  is substantially the same as the tip width  149  of the narrow teeth  130 , but these widths may be different in other embodiments. 
     The wide teeth  120  also include inboard and outboard transition portions  158   a  and  158   b  that extend from respective first or radially outer edges  160   a  and  160   b  to second or radially inner edges  162   a  and  162   b . The radial distance between the edges  160  and  162  can define a transition portion height  182  ( FIG. 13 ) that can be optionally be at least 55%, 65%, 70%, 75% or more of the tooth height  134 . In some embodiments, the widening portion of the tooth (e.g. the transition portions  158 ) may be larger in the axial direction than the portions of the tooth that are either of generally constant width and/or portions of the tooth that taper inwardly (e.g. toward the root in this example. Each of the edges  160   a,b  and  162   a,b  are configured such that they extend in a direction that is substantially parallel to the plane D, which is understood to encompass edges that are linear and parallel to plane D, as well as edges like edges  160   a,b  and  162   a,b  which have a slight curvature in the radial direction but are substantially parallel to plane D in the circumferential direction. The radially inner edges  162   a  and  162   b  are also positioned to be axially (or laterally) outboard of their respective radially outer edges  160   a  and  160   b . In this configuration, the transition portions  158   a  and  158   b  each tend to generally widen from edges  160  to edges  162 , which results in the wide teeth  120  generally widening along the transition portions  158   a  and  158   b.    
     At the lower (as illustrated in  FIGS. 12 and 13 ) edges  162   a  and  162   b  of the transition portions the wide teeth also include inboard and outboard edge surfaces  164   a  and  164   b  that extend generally parallel to plane D and away from the edges  162   a  and  162   b  in the radial direction. The edge surfaces may have an edge height in the radial direction that is between about 5% and about 15% of the transition height in some embodiments. The wide teeth  120  also include chamfers  168  for clearance and tooth top land face  170 . 
     In this example, the transition portions  158   a  and  158   b  are configured to be the portion of the wide teeth  120  that will contact the chain if it becomes misaligned and may help urge the chain back into lateral alignment with the chainring  100 . Preferably, the transition portions  158   a  and  158   b  are configured so that while the generally widen from the tip  132  toward the root  128  they widen more gradually than conventional chainring teeth so that a width  142  of the wide teeth  120  measured in plane A ( FIG. 11 ) is less than about 80% of the wide link width  60 , and may be between about 70-75% of the width  60 . Preferably, the plane A is located at a height  172  that can be between about 40% and about 60% of the tooth height  134 , and in the illustrated example is approximately 50% of the tooth height  134 . 
     Referring to  FIGS. 11 and 12 , in this arrangement the chamfers  26  and  46  of the outer chain links  22  and  42  may tend to contact and slide along the transition portions  158   a  or  158   b  (depending on the direction of misalignment). Referring to  FIG. 13 , plane C contains both edge  162   a  and edge  162   b  and is generally parallel to axis  104  of chainring  100 . When outer link set  20  is fully seated around wide tooth  120 , Plane C is spaced above the root by a height  186  that can be between about 5% and 20% of the tooth height  134  and is offset below inner faces  44  and  24  by a distance  184 . As such, outboard and inboard faces  134   a  and  134   b  do not contact inner faces  44  and  24 . 
     Because of the relatively gradual tapering of the wide teeth  120  the chain  10  may be urged into alignment with the chainring  100  more gradually (e.g. over a relatively larger rotational distance as the chainring rotates) than if the transition portions  158   a  and  158   b  widened more quickly (e.g. occupied 80% or more of the link width  60  at plane A). This may help reduce the forces exerted between the chain and the transition portions  158  of the wide teeth  120 , which may help reduce wear on the teeth and/or the chain. 
     In addition, the transition portions  158   a  and  158  can preferably be configured so that they continue to generally widen below plane A (e.g. radially inward of plane A—toward the root) to a second, wider width  176  that is measured at the lower edges  162   a  and  162   b  of the transition zones  158   a,b , which lie in and help define a second plane C, positioned between the plane A and the root  128 . Optionally, the second plane C may be positioned so that the height  186  is between about 10% and about 30% of the tooth height and may preferably be about 25% of the tooth height  134 . In this position the second plane C may be positioned so as to be disposed radially inward and will not intersect opposing active link faces  24  and  44  of the drive chain that bound the wide link spaces  58  when the wide tooth  120  is fully received within a corresponding one of the wide link spaces ( FIG. 13 ). 
     This width  176  is greater than the width  142  and may preferably be selected to be at least 105%, 110%, 115%, 120%, 125% or more of the width  142 . In this configuration, the chain  10  will continued to be urged into alignment with the chainring as it moves inward (downward as illustrated) past the midway point of the teeth  120 . Preferably, the width  176  can be set so that it is at least 90% of the wide link width  60 , and optionally can be set so that it is between 95-105% of width  60  and may be substantially the same as the wide link width  60 . This may help further guide the chain  10  into alignment as it continues to settle onto the teeth  120  as the chainring  100  rotates. Optionally, the width  176  may represent the widest point on the tooth  120 , and the tooth  120  then narrow inboard from faces  164   a,b  to a root width  138  that is less than the width  176  and optionally less than the width  142  and is measured in a plane  180  ( FIG. 13 ) that is parallel to planes A and C. 
     Referring also to  FIG. 27 , the location of plane C, and the lower edges  162   a  and  162   b  of the transition zones  158   a,b  is preferably set so that when the chain  10  is fully seated on the chainring  100  as shown in  FIG. 13  that the plane C is located radially inward from (below as illustrated in  FIGS. 13 and 27 ) and does not intersect the faces  24  and  44 , such that the lower edges  162   a  and  162   b  are inward from the faces  24  and  44  as well. This may help reduce the degree of contact/wear between the faces  24  and  44  and the lower edges  162   a  and  162   b  and faces  164   a,b  when the chain  10  is seated on the chainring. In this embodiment, each of the planes A and C are generally orthogonal to the radial direction and are positioned so that they lie radially within and intersect the transition portions  158   a  and  158   b  of the wide tooth  120 , and plane C can help define the radially inner boundary of the transition portions  158 . 
     Preferably, the transition portions  158  may be configured to include a single, continuous surface that extends between the outer and inner edges  160  and  162 . This surface would provide the generally continuously widening contact surface of the transition zones  158  and may be free from intervening edges, corners or other such features that may tend to wear faster when contacted by the chain  10 . Optionally, such a transition surface may be configured to generally match the profile of the associated link faces  22  and  42 , and may be flat, planar surfaces that are inclined relative to the plane D. Alternatively, the transitions surfaces may be configured as curved, arcuate surfaces that curve between the edges  160  and  162  but are configured such that tangents to the surfaces are generally parallel to the edge direction and plane D. The curved surfaces may optionally be configured as generally convex, fillet surfaces and optionally may have a generally constant radius of curvature. In yet other alternative embodiments, the transition portions may include two or more transition surfaces that may have different orientations but are preferably arranged so that the teeth generally widen along within the transition portions. 
     Referring to  FIGS. 5, 12 and 13 , the transition portions  158   a,b  of the wide teeth  120  in the present example each include a single, substantially planar transition surface  178   a  and  178   b  that is configured as a chamfer surface which extends continuously between the edges  160   a,b  and  162   a,b . These surfaces  178   a  and  178   b  are preferably relatively smooth to help facilitate sliding of the chain  10  and are inclined relative to the plane D such that they converge toward the tip  132  and generally widen toward the root  128 . In this example, as shown in  FIG. 12  when the chain is misaligned the chamfer  26  may in sliding contact with outboard wide tooth chamfer surface  178   a . The chamfer  26  can then slide down outboard wide tooth chamfer  178   a  and the inboard outer link plate  42  can move closer to chainring center plane D, thereby aligning outer link set  20  to chainring  100  as the chainring rotates (see  FIG. 13 ). 
     Optionally, the chainring  100  may be configured so that it is generally symmetrical around plane D. Referring now to  FIG. 6 , a radially extending plane E bisects top land  126  (see  FIG. 7 ) of wide tooth  120 . Wide tooth  120  in this example is symmetric about plane E. A radially extending plane F bisects top land  136  (see  FIG. 7 ) of narrow tooth  130 . Narrow tooth  130  in this example is symmetric about plane F in the direction of rotation  102 . 
     Referring to  FIGS. 14-23 , another example of a chainring  1100  that is compatible with the drive chain  10  is shown. Chainring  1100  is generally similar to chainring  100  with like features being annotated using like reference characters indexed by  1000 . When mounted to bicycle and the crankset is pedaled chainring  1100  is configured so that it will rotate in a rotation direction  102  (shown as clockwise in  FIG. 14 , but which could also be counter clockwise) about a rotation axis  1104 . 
     In this example, the chainring  1100  includes body  1110  and a mounting portion  1112  that is configured to be connected to a bicycle. The body surrounds and is rotatable about the rotation axis  1104  and helps define the plane D ( FIG. 19 ) that is shown as being in the middle of the body  1110  in the axial direction (i.e. parallel to rotation axis  1104 ). For the purposes of discussion, the chainring  1100  is described has having an outboard chainring face  1114   a  and an opposing inboard chainring face  1114   b  but it is understood that this orientation could be reversed if the chainring is connect to a bicycle in a different orientation. 
     In this example, the mounting portion  1112  includes a central mounting aperture  1180  instead of the plurality of spaced apart mounting apertures  105   a - 105   d . The aperture  1180  is configured to be connected to a corresponding attachment portion on a bicycle crank set. In other examples the mounting portion  1112  may have a different configuration. 
     The chainring  1100  also includes a periphery portion that surrounds the rotation axis  1104 . The periphery portion in the illustrated example includes an outer or root periphery region  1116  and an inner periphery region  1170  that is radially in inboard from the periphery region  1116 . A plurality of teeth extend generally radially outwardly from the outer periphery region  1116 , including a plurality of wide teeth  1120  arranged in an alternating manner with a plurality of relatively narrow teeth  1130 . In this example, the narrow teeth  1130  all have substantially the same shape as each other, as do the wide teeth  1120 . 
     In this example, the narrow teeth  1130  are generally similar to the narrow teeth  130  but are configured so that top land surface  1142  is smaller than top land surface  142 , and tip width  1156  is less than tip width  156 . The narrow teeth  1130  extend from respective roots  1122  that are proximate the body  1110  to respective tips  1124  that are spaced apart from the roots  1122  by a tooth height  1126 . 
     The wide teeth  1120  also extend from respective roots  1128  proximate the body  1110  to respective tips  1132  that are spaced from the roots  1128  by the wide tooth height  1134 . In the illustrated example the heights  1126  and  1134  are substantially equal, but in other examples may differ. Also, in this example the roots  1122  and  1128  of all of both types of teeth  1120  and  1130  lie along a common root groove  1136  that is formed on the body  1110  such that the roots  1122  and  1128  have substantially the same root width in the axial direction, one example of which is shown as root width  1138  in  FIG. 22 . 
     Referring to  FIGS. 21-23 , in this example, the wide teeth  1120  include respective drive faces  1152  for driving adjacent rollers  50  when in use and have a generally radially outwardly facing top land face  1154  at is located at the tip  1132  and defines a tip width  1156  ( FIG. 22 ). In this example, the tip width  1156  is different (and greater than) than the tip width  1149  of the narrow teeth  1130 . 
     The wide teeth  1120  also include inboard and outboard transition portions  158   a  and  158   b  that extend from respective first or radially outer edges  1160   a  and  1160   b  to second or radially inner edges  1162   a  and  1162   b  and that tend to generally widen from edges  1160  to edges  1162 , which results in the wide teeth  1120  generally widening along the transition portions  1158   a  and  1158   b.    
     At the lower (as illustrated in  FIGS. 22 and 23 ) edges  1162   a  and  1162   b  of the transition portions the wide teeth also include inboard and outboard edge surfaces  1164   a  and  1164   b  and chamfers  1168  for clearance and a tooth top land face  1170 . 
     In this example, the transition portions  1158   a  and  1158   b  are configured so that while the generally widen from the tip  1132  toward the root  1128  they widen more gradually than conventional chainring teeth so that a width  1142  of the wide teeth  1120  measured in plane A ( FIG. 21 ) is less than about 80% of the wide link width  60 , and may be between about 70-75% of the width  60 . Preferably, the plane A is located at a height  1172  that can be between about 40% and about 60% of the tooth height  1134 , and in the illustrated example is approximately 50% of the tooth height  1134 . 
     Referring to  FIGS. 21 and 22 , in this arrangement the chamfers  26  and  46  of the outer chain links  22  and  42  may tend to contact and slide along the transition portions  1158   a  or  1158   b  (depending on the direction of misalignment). Referring to  FIG. 23 , plane C contains both edge  1162   a  and edge  1162   b  and is generally parallel to axis  1104  of chainring  1100 . When outer link set  20  is fully seated around wide tooth  1120 , Plane C is spaced above the root by a height  1186  that can be between about 5% and 20% of the tooth height  1134  and is offset below inner faces  44  and  24  by a distance  1184 . As such, outboard and inboard faces  1134   a  and  1134   b  do not contact inner faces  44  and  24 . 
     In this example the transition portions  1158   a  and  1158  are configured so that they continue to generally widen below plane A (e.g. radially inward of plane A—toward the root) to a second, wider width  1176  that is measured at the lower edges  1162   a  and  1162   b  of the transition portions  1158   a,b , which lie in and help define a second plane C, positioned between the plane A and the root  1128 . 
     In this embodiment, this width  1176  is greater than the width  1142  and may preferably be selected to be at least 105%, 110%, 115%, 120%, 125% or more of the width  1142 . In this configuration, the chain  10  will continued to be urged into alignment with the chainring as it moves inward (downward as illustrated) past the midway point of the teeth  1120 . Preferably, the width  1176  can be set so that it is at least 90% of the wide link width  60 , and optionally can be set so that it is between 95-105% of width  60  and may be substantially the same as the wide link width  60 . This may help further guide the chain  10  into alignment as it continues to settle onto the teeth  1120  as the chainring  100  rotates. Optionally, the width  1176  may represent the widest point on the tooth  120 , and the tooth  1120  then narrow inboard from faces  1164   a,b  to a root width  1138  that is less than the width  1176  and optionally less than the width  1142 . 
     Referring to  FIGS. 15, 22 and 23 , the transition portions  1158   a,b  of the wide teeth  11120  in the present example each include a single, substantially planar transition surface  1178   a  and  1178   b  that is configured as a chamfer surface which extends continuously between the edges  1160   a,b  and  1162   a,b.    
     Referring to  FIG. 24 , a schematic representation of another example of a width tooth  2120  that can be used with the chainrings and chains described herein. The tooth  2120  is generally similar to the wide tooth  120  and like features are annotated using like reference characters indexed by  2000 . In this embodiment the transitions surfaces  2178   a  and  2178   b  are configured as arcuate, fillet surfaces instead of planar, chamfer surfaces. 
     Referring to  FIG. 25 , a schematic representation of another example of a width tooth  3120  that can be used with the chainrings and chains described herein. The tooth  3120  is generally similar to the wide tooth  120  and like features are annotated using like reference characters indexed by  3000 . In this embodiment the transition portions  3158   a  includes two transition surfaces  3188   a  and  3190   a  instead of a single continuous surface  178   a . The transition surfaces  3188   a  and  3190   a  are each configured as flat, planar surfaces that are inclined relative to the central plane D and to each other. The transition portion  3158   b  has a matching configuration. 
     Referring to  FIG. 26 , a schematic representation of another example of a width tooth  4120  that can be used with the chainrings and chains described herein. The tooth  4120  is generally similar to the wide tooth  120  and like features are annotated using like reference characters indexed by  4000 . In this embodiment the transitions surfaces  4178   a  and  4178   b  are configured as planar, chamfer surfaces that converge to a relatively sharp point at the tooth tip  4132  such that there is no material top land surface in this example, and the tip width can be understood to be small and possibly be represented as an edge at the interface between the surfaces  4178   a  and  4178   b.