Patent Description:
All mountain bikes are offered in several sizes to fit riders of different heights. The parameters that define rider fit are collectively called the rider cockpit. The rider cockpit is made up of <NUM> primary contact points, <NUM>) the rider's foot to pedal, <NUM>) the rider's posterior to saddle, <NUM>) the rider's hand to handlebar. The distance between these contact points depends on the size of rider. A taller rider will require a larger effective "rider cockpit" (longer distances between contact points) than a shorter rider. <FIG> depicts common measurements of bicycles. Two primary measurements of the rider cockpit include "stack" and "reach. " Stack refers to the vertical distance measured from the bottom bracket of the bicycle to a horizontal datum aligned with the top of the bicycle's head tube. Reach refers to a horizontal distance from the top of the bicycle's headtube to a vertical datum aligned with the bicycle's bottom bracket. Seat height on a bicycle is often adjustable through a seat post that may telescopically engage a seat tube of the bicycle. In addition, the placement of the handlebars may be adjusted through use of spacers, different sized stems, or the like. However, the stack and reach are fixed values for a given bicycle frame, as are the seat tube angle and head tube angle (which effects the "rake" of the fork of the bicycle). Bicycles are currently built around the rider cockpit, defined by the stack and reach described above.

The rider cockpit dimensions define many other performance attributes of the bike. For example, wheelbase is the distance between the front and rear wheel. The wheelbase may affect a bicycle's performance attributes. For example, a shorter wheelbase results in a more maneuverable, but less stable bike. Conversely, a longer wheelbase results in a more cumbersome (e.g., less maneuverable), but more stable bike. Due to the bicycle architecture (front wheel connected to fork, connected to headtube, connected to stem, connected to handlebar), wheelbase is directly proportional to rider cockpit. So, a bike designed to fit a shorter rider will have a proportionally shorter wheelbase, and a bike designed to fit a taller rider will have a proportionally longer wheelbase. This means the vehicle performance attributes are directly tied to the size of rider. A shorter rider has no choice but to ride a bike that is more maneuverable, but less stable. And a taller rider has no choice but to ride a more cumbersome, but more stable bike. Accordingly, the current paradigm governing bicycle design ties certain bicycle geometries that affect the vehicle performance with the rider cockpit dimensions such that vehicle performance characteristics are directly tied to the size of the bicycle required to fit a given sized rider.

An example of an assembly known in the art is disclosed in <CIT>. Document <CIT> shows: A steering linkage assembly for a bicycle, comprising:a linkage chassis comprising a steering tube that defines a steering tube axis, wherein the steering tube axis is offset from a headtube axis of a headtube of the bicycle, wherein the steering tube axis is offset a greater distance from a seat of the bicycle than the headtube axis; a fork steerer configured for co-rotation with a fork of the bicycle, wherein the fork steerer is engaged with a fork tube that is positioned in the headtube; a handlebar steerer configured for co-rotation with handlebars, wherein the handlebar steerer is engaged with a steering spindle that is positioned in the steering tube; one or more linkage member extending between the fork steerer and the handlebar steerer to impart co-rotational movement between the handlebar steerer and the fork steerer, the linkage member being disposed on a side of the linkage chassis opposite that on which the handlebars are attached to the steering spindle for uninterrupted movement of the linkage members by the headtube of the bicycle or the linkage chassis a headtube reference surface of the headtube on a side of the headtube opposite the fork; and a steering tube reference surface on a side of the steering tube adjacent to an attachment location of the handlebars.

In view of the foregoing, the present disclosure relates to a steering linkage for a bicycle. By use of a steering linkage as described herein, the rider cockpit sizing is effectively divorced from the overall bicycle performance geometry parameters such that the dependence on rider size as a factor for bicycle performance characteristic is reduced or eliminated. That is, by use of the steering linkage described herein, rider cockpit dimensions (e.g., reach and stack) may be established to fit a rider while not effecting the geometry of the bicycle that affect vehicle performance such as wheelbase, fork rake, and the like. That is, the purpose of the steering linkage is to disassociate the "rider cockpit" from "vehicle performance attributes. " For example, a bike using the steering linkage described herein can have a "rider cockpit" to fit a taller rider but have a shorter wheelbase to provide a more dynamic vehicle performance attribute. Conversely, the presently described steering linkage may allow a shorter rider to fit a longer wheelbase bicycle to provide a more stable vehicle performance attribute. In short, the rider can now decide what kind of vehicle performance attributes the rider wants, independent of rider cockpit fit.

Accordingly, the present disclosure generally relates to a steering linkage assembly. The steering linkage assembly includes a linkage chassis, a fork steerer, a handlebar steerer, and one or more linkage member. The linkage chassis includes a steering tube having a steering axis that is offset from a headtube axis defined by a headtube of a bicycle frame. The linkage chassis may be integrated with a bicycle frame or may comprise a separate component that may be affixed to the bicycle frame (e.g., at the headtube).

In any regard, the fork steerer is configured for co-rotation with a fork of the bicycle frame and the handlebar steerer is configured for co-rotation with handlebars. Additionally, the linkage member extends between the fork steerer and the handlebar steerer to impart co-rotational movement between the handlebar steerer and the fork steerer. The linkage member is disposed on a side of the linkage chassis opposite the handlebars for uninterrupted movement of the linkage member by the bicycle frame or the linkage chassis.

As described above, the present disclosure generally relates to a steering linkage for a bicycle that allows certain rider cockpit dimensions and vehicle performance attributes to be independently controlled.

<FIG> illustrates an exploded view of an example of a linkage chassis <NUM> that may be secured to a bicycle frame <NUM>. The linkage chassis <NUM> may securely attach to mating features <NUM> located on the front of the headtube <NUM>. For instance, the mating features <NUM> may include threaded holes for receipt of fasteners <NUM>. In turn, the linkage chassis <NUM> may be attached and removed using common tools. This allows the user to swap out different length linkage assemblies in order to fine tune the dimensions of the rider cockpit (e.g., reach and/or stack) independently of the vehicle performance attributes such as bicycle wheelbase, which may remain unaffected as the headtube <NUM> remains unchanged. As will be described in greater detail below, this may allow a kit to be provided to allow for a modification of an offset length between a headtube axis <NUM> of the bicycle frame <NUM> and a steering axis <NUM> of the linkage chassis <NUM> defined by a steering tube <NUM> of the linkage chassis <NUM>.

Additionally, the user can opt to remove the linkage chassis <NUM> and any associated steering linkage assembly at all, instead setting the bike up with a traditional fork/handlebar orientation. This convenient range of size options effectively isolates the rider cockpit from the vehicle size, allowing any size rider to fit onto any size/length bike. Different kinds of riding demand different kind/size bikes.

In an alternative example, the linkage chassis <NUM> may be integrated with the bicycle frame <NUM>. Therefore, in the following discussion, the attributes of the linkage chassis <NUM> may generally be provided regardless of whether the linkage chassis <NUM> is provided as separate, attachable component to the bicycle frame <NUM> or integrated with a bicycle frame <NUM>. Specifically, with reference to <FIG>, the linkage chassis <NUM> is shown with respect to the bicycle frame <NUM>. It may be appreciated that the linkage chassis <NUM> may be arranged as shown in <FIG> whether integral or separate from the frame <NUM>. In any regard, with use of the linkage chassis <NUM>, a headtube <NUM> and a steering tube <NUM> may be provided that are offset by an offset length as described herein. Thus, while an attachable/detachable linkage chassis <NUM> is shown and described herein, the present disclosure is not so limited and may include such an integrated configuration without limitation.

With returned reference to <FIG>, examples of a steering linkage assembly <NUM> is shown. The steering linkage assembly <NUM> includes the linkage chassis <NUM> including the steering tube <NUM>. The steering linkage assembly <NUM> includes a fork steerer <NUM> and a handlebar steerer <NUM> connected by way of one or more linkage member such as linkage bars <NUM>. The fork steerer <NUM> is configured for co-rotation with a fork <NUM> of the bicycle frame <NUM>. The fork steerer <NUM> may be clampingly engaged to a fork tube <NUM> that extends through the headtube <NUM> along the headtube axis <NUM>. The fork tube <NUM> may move relative to the headtube <NUM> by way of rotational bearings disposed between the headtube <NUM> and the fork tube <NUM>. In any regard, the fork steerer <NUM> may co-rotational with the fork <NUM> (e.g., by way of the clamping engagement with the fork tube <NUM>).

The handlebar steerer <NUM> may be engaged with a steering spindle <NUM> that may extend through the steering tube <NUM> of the linkage chassis <NUM>. The steering spindle <NUM> may be rotatable relative to the steering tube <NUM> by way of rotational bearings. The handlebar steerer <NUM> may be co-rotational with the steering spindle <NUM>. For example, the handlebar steerer <NUM> may be clampingly engaged with, integral with, or otherwise configured for co-rotation with the steering spindle <NUM>. The steering spindle <NUM> may be affixed with a stem <NUM> that, in turn, engages handlebars <NUM>. In turn, rotation of the handlebars <NUM> results in co-rotation of the steering spindle <NUM> and the handlebar steerer <NUM>.

The handlebar steerer <NUM> and the fork steerer <NUM> may be connected by way of a plurality of linkage members to effectuate co-rotation of the fork steerer <NUM> and the handlebar steerer <NUM>. In the depicted example, the linkage members comprise rigid linkage bars <NUM> extending between the fork steerer <NUM> and the handlebar steerer <NUM>. The linkage bars <NUM> may each be rotationally engaged at a first end thereof with the fork steerer <NUM> and at a second end thereof with the handlebar steerer <NUM>. In turn, the fork steerer <NUM>, handlebar steerer <NUM>, and the linkage bars <NUM> define a linkage (e.g., a four bar linkage). The linkage results in co-rotation of the fork steerer <NUM> and the handlebar steerer <NUM>. In turn, when a rider turns the handlebars <NUM>, rotation is transmitted to the handlebar steerer <NUM>, to the fork steerer <NUM>, and on to the fork <NUM> to turn the bicycle's wheel (not shown).

The linkage defined by the fork steerer <NUM>, handlebar steerer <NUM>, and the linkage bars <NUM> is located on the underside of the main frame headtube <NUM> (i.e., a side adjacent to the fork <NUM> or nearest the ground when the bicycle frame <NUM> is supported by wheels). Stated differently, the linkage bars <NUM> may be located on a side of the linkage chassis <NUM> opposite that which the handlebars <NUM> are attached to the steering spindle <NUM>. The fork steerer <NUM> of the steering linkage assembly <NUM> may be provided between a fork crown <NUM> and a lower bearing race <NUM> of the headtube <NUM>. The handlebar steerer <NUM> may be located below the linkage chassis <NUM>. This orientation may provide advantages over other layouts in that it allows a greater overall range of rotational motion. As the assembly rotates each linkage bar <NUM> can sweep underneath the handlebar steerer <NUM> and the linkage chassis <NUM>. In contrast, if the linkage assembly was located on top or somewhere mid elevation, the steering range of rotational motion would be significantly reduced due to contact between one or more of the linkage bars <NUM> and the handlebar steerer <NUM>.

Additionally or alternatively, the steering linkage assembly <NUM> may be configured such that the linkage bars <NUM> sweep underneath the fork steerer <NUM>. Again, this arrangement allows for improved steering angle by precluding interference between the linkage bars <NUM> and the fork steerer <NUM>. Further still, and as will be described in greater detail below integration of the fork steerer <NUM> into fork crown <NUM> may also be provided to increase steering angle range.

Use of the steering linkage assembly <NUM> may allow rider handlebar height to be adjusted with a number of components (e.g., including stem length and angle, steerer spacer stack <NUM> height (best seen in <FIG>), and handlebar rise and sweep). While all these adjustments may be provided in traditional bicycle geometries relative to the top of the headtube <NUM> on a traditional bike, adjustment of this base position is limited by the structural limitations of the frame and fork. That is, all adjustments of the handlebars <NUM> are still limited by the fact the handlebars <NUM> must be provided above the top portion of the headtube <NUM>. In this regard, the handlebar height adjustment when using the steering linkage assembly <NUM> may be configured in relation to the offset distance <NUM> of the linkage chassis <NUM> between the headtube axis <NUM> and the steering axis <NUM> of the steering linkage assembly <NUM>. In addition, the steering linkage assembly <NUM> architecture allows more freedom to adjust handlebar height because the base position for mounting the handlebars can be located significantly lower than the top of the frame's headtube <NUM>. That is, the steering tube <NUM> may terminate in a manner that is offset from the termination of the headtube <NUM>. This may allow the components mounting the handlebars <NUM> to be provided at a distance offset in a direction toward the ground when the bicycle is upright on the wheels of the bicycle. This may allow for more flexibility when adjusting the rider cockpit by allowing the handlebars <NUM> to be mounted relatively lower than can be accomplished when mounting the handlebars <NUM> relative to the headtube <NUM>.

Further still, the fork steerer <NUM> and the handlebar steerer <NUM> may also be configured to provide leveraged actuation upon co-rotation of the fork steerer <NUM> and the handlebar steerer <NUM>. For instance, the fork steerer <NUM> and the handlebar steerer <NUM> may be different lengths or arranged relative to one another such that the amount of given rotation between the fork steerer <NUM> and the handlebar steerer <NUM> is not equal as the fork steerer <NUM> and the handlebar steerer <NUM> undergo co-rotation. That is, co-rotation does not require an identical amount of rotation of the fork steerer <NUM> and the handlebar steerer <NUM>. Rather, while co-rotation may include equal amounts of rotation of the fork steerer <NUM> and the handlebar steerer <NUM>, steering input may alternatively be amplified or dampened relative to actual movement of the fork <NUM>. That is, for a given amount of rotation of the handlebar steerer <NUM> a different amount of rotation (e.g., more or less) of the fork steerer <NUM> and the fork <NUM> may be provided. For instance, steering may be made more responsive such that for a given amount of rotation of the handlebar steerer <NUM> results in a greater amount of rotation of the fork steerer <NUM> and the fork <NUM>. Alternatively, steering may be dampened such that for a given amount of rotation of the handlebar steerer <NUM> results in a smaller amount of rotation of the fork steerer <NUM> and the fork <NUM>. As described above, this may be achieved through different lengths of the fork steerer <NUM> and the handlebar steerer <NUM> between the linkage bars <NUM>. Alternatively, in embodiments described below that utilize a continuous, flexible linkage member, the fork steerer <NUM> and the handlebar steerer <NUM> may have different diameters to achieve different amounts of rotation between the fork steerer <NUM> and the handlebar steerer <NUM>.

In the example depicted, two independent linkage bars <NUM> are utilized in this architecture. This redundancy is a key safety benefit, if failure occurs in one link, there is a second to maintain a functional connection.

With further reference to <FIG>, another example of a steering linkage assembly <NUM>. The example depicted in <FIG> may generally include each feature recited above in relation to <FIG>. In this regard, while reference numerals for the example shown in <FIG> were in the form 1XX, corresponding components are labeled as 2XX in the example shown in <FIG>.

In addition, the example shown in <FIG> generally includes an integrated fork steerer such that the link bars <NUM> directly engage the fork <NUM> (e.g., at a fork crown <NUM>). In this regard, the fork <NUM> may be directly acted on by the link bars <NUM> to co-rotate the fork <NUM> upon rotation of the handlebars <NUM> by a rider. This may provide an increased turning angle range.

<FIG> depicts another example of a steering linkage assembly <NUM>. The steering linkage assembly <NUM> may include features as generally described above in relation to the examples of the steering linkage assembly <NUM> and the steering linkage assembly <NUM>. In contrast to the foregoing steering linkage assembly examples that utilize a fork steerer and handlebar steerer connected by linkage members comprising rigid linkage bars, the steering linkage assembly <NUM> may include a linkage member comprising a flexible linkage member <NUM>. The flexible linkage member <NUM> may comprise a continuous body such that the flexible linkage member <NUM> may comprise a chain, belt, or other flexible member. The flexible linkage member <NUM> may extend about a fork steerer <NUM> and a handlebar steerer <NUM> such that the fork steerer <NUM> and the handlebar steerer <NUM> are engaged for co-rotation.

The fork steerer <NUM> and/or handlebar steerer <NUM> may include engagement features that correspond to the flexible linkage member <NUM> to facilitate engagement between the flexible linkage member <NUM> and the fork steerer <NUM> and/or handlebar steerer <NUM>. For instance, the fork steerer <NUM> and/or handlebar steerer <NUM> may include teeth, splines, or other features. In this regard, the fork steerer <NUM> and/or handlebar steerer <NUM> may comprise a gear, sprocket, splined shaft, or the like. The flexible linkage member <NUM> may have corresponding engagement features such as teeth, ridges, or other features that engage the fork steerer <NUM> and/or handlebar steerer <NUM>.

While not shown in <FIG>, the flexible linkage member <NUM> may be appropriately tensioned to maintain engagement with the fork steerer <NUM> and handlebar steerer <NUM> to effectuate co-rotation thereof. For instance, a first section 336a of the flexible linkage member <NUM> may extend between the fork steerer <NUM> and handlebar steerer <NUM> on a first side thereof and a second section 336b of the flexible linkage member <NUM> may extend between the fork steerer <NUM> and handlebar steerer <NUM> thereof. In this regard, the first section 336a and the second section 336b may comprise linkage members extending between the fork steerer <NUM> and handlebar steerer <NUM> to effectuate co-rotation thereof.

Also, while the fork steerer <NUM>, handlebar steerer <NUM>, and flexible linkage member <NUM> are shown as being disposed entirely beyond the profile of the linkage chassis <NUM> on a side thereof opposite the handlebars <NUM>, it may be appreciated that at least a portion of or all of the fork steerer <NUM>, handlebar steerer <NUM>, and flexible linkage member <NUM> may be disposed internally within the linkage chassis <NUM>.

In this regard, the steering linkage assembly <NUM> may provide some noted benefit including a potential larger angular range of motion and potentially comprising a smaller volume profile to allow for smaller packaging (e.g., including internalizing the assembly to the linkage chassis <NUM> as described above).

With further reference to <FIG>, an example of a steering linkage assembly <NUM> in which a steering spindle <NUM> is disposed in a headtube <NUM> of a bicycle frame <NUM>. In turn, a fork tube <NUM> may be disposed in a steering tube <NUM> of the steering linkage assembly <NUM>. In this regard, the fork <NUM> may be rotatable about the steering axis <NUM> of the steering tube <NUM> and the steering spindle <NUM> may be rotatable about the headtube axis <NUM>. That is, the steering spindle <NUM> and the fork tube <NUM> may be in an inverted position from those shown in <FIG>. A fork steerer <NUM> may still be connected to a handlebar steerer <NUM> through a linkage member <NUM> as described above to facilitate corotation of the steering spindle <NUM> and the fork <NUM>. When in the position shown in <FIG>, the wheelbase of the bicycle frame <NUM> may be lengthened relative to the reach of the rider as the handlebars <NUM> may be in a closer position to the rider by virtue of the offset between the steering axis <NUM> and the headtube axis <NUM>. Moreover, the fork <NUM> and the steering spindle <NUM> may be interchangeably positionable between the position shown in <FIG> and those shown in <FIG> to allow for selectable configuration of the bicycle frame <NUM> by a user.

One general aspect of the present disclosure includes a steering linkage assembly for a bicycle. The steering linkage assembly includes a linkage chassis. The steering linkage assembly includes a steering tube that defines a steering tube axis. The steering tube axis is offset from a headtube axis of a headtube of the bicycle. The assembly also includes a fork steerer configured for co-rotation with a fork of the bicycle. The fork steerer is engaged with a fork tube that is positionable into one of the steering tube or the headtube. The assembly also includes a handlebar steerer configured for co-rotation with handlebars. The handlebar steerer is engaged with a steering spindle that is positionable into the other of the steering tube or the headtube. The assembly also includes one or more linkage members extending between the fork steerer and the handlebar steerer to impart co-rotational movement between the handlebar steerer and the fork steerer. The plurality of linkage members are disposed on a side of the linkage chassis opposite that on which the handlebars are attached to the handlebar steerer for uninterrupted movement of the linkage members by the headtube of the bicycle or the linkage chassis.

Implementations may include one or more of the following features. For example, the steering linkage assembly may include a headtube reference surface of the headtube on a side of the headtube opposite the fork. In addition, a steering tube reference surface may be on a side of the steering tube adjacent to an attachment location of the handlebars. The steering tube reference surface may be offset from the headtube reference surface in a direction toward the fork of the bicycle.

In an example, the linkage members may include linkage bars. The fork steerer and the handlebar steerer may rotate through a steering angle range limited only by contacting engagement of the linkage bars with each other.

In an example, the fork steerer may be integrated into the fork of the bicycle.

In an example, the linkage members may include segments of a continuous flexible linkage member extending about the fork steerer and the handlebar steerer.

The linkage chassis may be integrated into a frame of the bicycle. Alternatively, the linkage chassis may be separate from a frame of the bicycle and configured for attachment to the headtube of the bicycle. In this regard, a kit may be provided that includes a plurality of linkage chasses, each having a different offset length between the steering tube axis and the headtube axis. The kit may also include a plurality of linkage bar sets, each having different lengths corresponding to a given one of the plurality of linkage chasses. In turn, respective ones of the plurality of linkage chasses and linkage bar sets may be attachable to the fork steerer and the handlebar steerer, respectively, to define the different offset lengths between the steering tube axis and the headtube axis.

In an example, the steering spindle may be disposed in the steering tube and the fork tube is disposed in the headtube. Alternatively, the fork tube is disposed in the steering tube and the steering spindle is disposed in the headtube.

Another general aspect includes a bicycle. The bicycle includes a bicycle frame that has a headtube having a headtube axis. The bicycle also includes a linkage chassis that includes a steering tube that defines a steering tube axis. The steering tube axis is offset from the headtube axis of the headtube of the bicycle. The bicycle also includes a fork steerer configured for co-rotation with a fork of the bicycle. The fork steerer is engaged with a fork tube that is positionable into one of the steering tube or the headtube. The bicycle also includes a handlebar steerer configured for co-rotation with handlebars. The handlebar steerer is engaged with a steering spindle that is positionable into the other of the steering tube or the headtube. The bicycle also includes linkage members extending between the fork steerer and the handlebar steerer to impart co-rotational movement between the handlebar steerer and the fork steerer. The linkage members may be disposed on a side of the linkage chassis opposite that on which the handlebars are attached to the handlebar steerer for uninterrupted movement of the linkage members by the headtube of the bicycle or the linkage chassis.

Implementations may include one or more of the following features. For example, the bicycle may include a bottom bracket that defines a reach measurement and a stack measurement in relation to the headtube. The reach measurement may include a horizontal distance measured between the headtube and a vertical datum aligned with the bottom bracket. The stack measurement may include a vertical distance measured between the bottom bracket and a horizontal datum aligned with the headtube. The offset between the steering tube axis and the headtube axis may be defined independent of the reach measurement and the stack measurement.

In an example, the bicycle may include a headtube reference surface of the headtube on a side of the headtube opposite the fork. Also, a steering tube reference surface may be defined on a side of the steering tube adjacent to an attachment location of the handlebars. The steering tube reference surface may be offset from the headtube reference surface in a direction toward the fork of the bicycle.

In an example, the linkage members may include linkage bars. The fork steerer and the handlebar steerer may rotate through a steering angle range limited only by contacting engagement of the linkage bars with each other. Alternatively, the linkage member may include segments of a continuous flexible linkage member extending about the fork steerer and the handlebar steerer.

In an example, the linkage chassis may be integrated into a frame of the bicycle. Alternatively, the linkage chassis is separate from a frame of the bicycle and configured for attachment to the headtube of the bicycle frame. In this regard, a kit may be provided that includes a plurality of linkage chasses, each having a different offset length between the steering tube axis and the headtube axis. The kit may also include a plurality of linkage bar sets, each having different lengths corresponding to a given one of the plurality of linkage chasses. In turn, respective ones of the plurality of linkage chasses and linkage bar sets may be attachable to the fork steerer and the handlebar steerer, respectively, to define the different offset lengths between the steering tube axis and the headtube axis.

Claim 1:
A steering linkage assembly (<NUM>) for a bicycle, comprising:
a linkage chassis (<NUM>) comprising a steering tube (<NUM>) that defines a steering tube axis (<NUM>), wherein the steering tube axis (<NUM>) is offset from a headtube axis (<NUM>) of a headtube (<NUM>) of the bicycle, wherein the steering tube axis (<NUM>) is offset a greater distance from a seat of the bicycle than the headtube axis (<NUM>);
a fork steerer (<NUM>) configured for co-rotation with a fork (<NUM>) of the bicycle, wherein the fork steerer (<NUM>) is engaged with a fork tube (<NUM>) that is positioned in the headtube (<NUM>);
a handlebar steerer (<NUM>) configured for co-rotation with handlebars (<NUM>), wherein the handlebar steerer (<NUM>) is engaged with a steering spindle (<NUM>) that is positioned in the steering tube (<NUM>);
one or more linkage member (<NUM>) extending between the fork steerer (<NUM>) and the handlebar steerer (<NUM>) to impart co-rotational movement between the handlebar steerer (<NUM>) and the fork steerer (<NUM>), the linkage member (<NUM>) being disposed on a side of the linkage chassis (<NUM>) opposite that on which the handlebars (<NUM>) are attached to the steering spindle (<NUM>) for uninterrupted movement of the linkage members by the headtube (<NUM>) of the bicycle or the linkage chassis (<NUM>);
a headtube reference surface of the headtube (<NUM>) on a side of the headtube (<NUM>) opposite the fork (<NUM>); and
a steering tube reference surface on a side of the steering tube (<NUM>) adjacent to an attachment location of the handlebars (<NUM>), the steering tube reference surface being offset from the headtube reference surface in a direction toward the fork (<NUM>) of the bicycle.