Patent Publication Number: US-2020298621-A1

Title: Axle housing extension member and method for adjusting track width of a truck axle

Description:
FIELD OF THE DISCLOSURE 
     The disclosure relates generally to adjustment of track width of a truck axle. In particular aspects, the disclosure relates to an axle housing extension member configured for attachment to an axle flange of a truck to modify the truck from a standard track configuration to a wider track configuration, such as may be desirable to reconfigure an axle originally intended to receive a dual-tire wheel assembly to instead receive a single wide (or “super single”) wheel. 
     BACKGROUND 
     One way of improving fuel economy in heavy trucks is to replace dual rear tires with super single rear tires to reduce rolling resistance and weight. A significant contributor to rolling resistance is energy loss due to tire sidewall deformation, and the conversion of dual-tire assemblies to super single tires inherently reduces the number of tire sidewalls per axle by half. Replacing standard width truck axles with wider track axles specifically suited for super single rear tires can be difficult and expensive. However, if a truck operation simply fits wheels having super single tires to a standard truck axle, maintenance problems may result. 
     A super single wheel includes a wheel hub that is offset in an outboard direction relative to a dual tire wheel. As explained with reference to  FIGS. 1A-1C , mounting super single rear tires to a standard track rear axle may shift a mechanical load center applied between inner and outer wheel bearings, creating uneven wheel bearing loads, causing, in turn, premature wheel bearing and/or spindle failure. Increasing loading on an outer wheel bearing may be particularly troublesome when an outer wheel bearing is smaller than an inner wheel bearing (i.e., to accommodate a tapered spindle). Premature failure leads to increased maintenance costs to replace wheel bearings after a short service life, as well as the cost of down time of the vehicle. Additionally, such a configuration leads to a narrower overall track width which may compromise handling of the vehicle. 
       FIG. 1A  is a perspective view of a truck axle housing  100 . The truck axle housing  100  includes a central housing portion  102  with a left arm  104 A and a right arm  104 B extending from opposite sides of the central housing portion  102  (left and right being relative to the drawing). At a distal or outboard end of the left arm  104 A is a left axle flange  106 A, and at a distal end of the right arm  104 B is a right axle flange  106 B. Each of the left and right axle flanges  106 A,  106 B (generally referred to as axle flange  106 ) includes a plurality of circumferentially spaced apertures  108  for mounting a brake assembly thereto. A left spindle  110 A extends from a distal end of the left axle flange  106 A and a right spindle  1108  (not shown) extends from a distal end of the right axle flange  106 B. The left and right spindles  110 A,  1108  (referred to generally as spindle  110 ) provide supporting surfaces for wheel bearings. A left axle shaft flange  112 A is arranged at an outboard end of the left spindle  110 A, and a right axle shaft flange  112 B (not shown) is arranged at an outboard end of the right spindle  1108 . Each of the left and right outboard axle shaft flanges  112 A,  112 B includes a plurality of circumferentially spaced apertures  114  for mounting a wheel thereto. 
       FIGS. 1B and 1C  are cross-sectional views illustrating for comparison loading of a dual wheel assembly and a super single wheel assembly, as if both were mounted on a standard track width axle configuration. In particular,  FIG. 1B  is a cross-sectional view of a dual tire wheel  116  as if mounted on a truck axle having a standard track configuration, with the truck load line A-A being substantially centered between inner and outer wheel bearings  120 A,  120 B. The inner wheel bearing  120 A is larger in diameter than the outer wheel bearing  120 B, to accommodate a tapered spindle.  FIG. 1C  is a cross-sectional view of a super single wheel  118  as if mounted on a truck axle also having a standard track configuration, showing the load line A′-A′ being outboard relative to the dual wheel assembly, positioned substantially closer to the outer wheel bearing  120 B than to the inner wheel bearing  120 A. The unbalanced loading in the illustrated super single wheel applies increased stress on the outer wheel bearing  120 B and may result in accelerated wear leading to premature bearing failure. 
     To avoid premature wear of wheel bearings, super single wheels should be used with truck axles having a track configuration wider than a standard track configuration suitable for use with dual tire wheels. However, retrofitting a truck to replace an axle having standard track configuration with an axle having a wider track configuration is time-consuming, complicated, and expensive. Such a retrofit may include expenses such as the cost of a replacement axle tandem as well as the labor to swap out the axles, hubs, brakes, etc. 
     Accordingly, the art continues to seek structures and methods for permitting an axle track width to be adjusted with reduced time, expense, and waste. 
     SUMMARY 
     Aspects of the disclosure relate to an axle housing extension member (also referred to here as an axle extension member) and method that permits the track width of a truck axle to be adjusted (e.g., widened). In particular, aspects of the disclosure relate to an axle extension member configured for attachment to an axle flange of a truck to modify the truck axle from a standard track configuration to a wider track configuration suitable for a super single type tire and wheel, as well as methods for adjusting track width of the truck axle. An exemplary axle extension member includes an annular spacer portion and a spindle portion configured to receive an extended length axle shaft extending through aligned internal bores defined through the annular spacer portion and the spindle portion, respectively. The annular spacer portion includes an end face configured to abut an outboard face of the axle flange. The thickness of the annular spacer portion exceeds the thickness of the axle flange by an amount sufficient to adjust a track width of the truck axle from a standard track configuration to a wider track configuration suitable for receiving a super single wheel. Accordingly, the axle extension member provides for retrofit mounting of super single wheels, advantageously locating the load center in a more neutral position between inner and outer wheel bearings. 
     In one aspect, an axle extension member is configured for attachment to an axle flange of a truck to modify the axle from a standard track configuration to a wider track configuration. The axle extension member comprises an annular spacer portion and a spindle portion. The annular spacer portion comprises an end face defining an inboard end of the axle extension member. The end face is configured to abut an outboard face of the axle flange. The spindle portion extends from the annular spacer portion and defines an outboard end of the axle extension member opposite the annular spacer portion, wherein the spindle portion comprises wheel bearing support surfaces configured to receive wheel bearings of a hub. The annular spacer portion defines a first internal bore. The spindle portion defines a second internal bore aligned with the first internal bore along a central axis. The first and second internal bores are configured to receive an extended length axle shaft. 
     In certain embodiments, the annular spacer portion and the spindle portion are embodied in a unitary member. In certain embodiments, the axle extension member further comprises a welded interface between the annular spacer portion and the spindle portion. 
     In certain embodiments, the annular spacer portion defines a plurality of circumferentially spaced apertures extending through the end face in a direction substantially parallel to the central axis. The plurality of circumferentially spaced apertures is aligned with a plurality of circumferentially spaced holes defined in the axle flange. The plurality of circumferentially spaced apertures is configured to receive a plurality of bolts to permit the axle extension member to be attached to the axle flange. In certain embodiments, each aperture of the plurality of circumferentially spaced apertures extends through an entire thickness of the annular spacer portion. 
     In certain embodiments, the first internal bore is sized and shaped to receive therein a retained spindle segment extending in an outboard direction from the axle flange. In certain embodiments, the first internal bore is sized and shaped to contact at least a portion of an outer wall of the retained spindle segment when the retained spindle segment is received within the first internal bore. In certain embodiments, a wall of the annular spacer portion defines a plurality of radially extending holes configured to receive a plurality of set screws configured to press against an outer surface of the retained spindle segment. 
     In certain embodiments, an outboard segment of the second internal bore comprises a first diameter, and an inboard segment of the second internal bore comprises a second diameter that is greater than the first diameter. 
     In certain embodiments, at least one of the annular spacer portion or the spindle portion comprises forged steel. 
     In certain embodiments, the axle extension member further comprises a brake mounting region defining at least one attachment feature configured for attachment of a disc brake assembly to the axle extension member. 
     In certain embodiments, the wheel bearing support surfaces are configured to receive rotational surfaces of inner and outer wheel bearings arranged to permit rotation of a single hub piloted wheel having a width of at least about 28 cm. In certain embodiments, when the rotational surfaces of the inner and outer wheel bearings are received on the wheel bearing support surfaces, a vertical load center applied on the single hub piloted wheel is substantially centered between the inner and outer wheel bearings. 
     In another aspect, a truck comprises at least one axle extension member, the at least one axle extension member comprising the axle extension member as disclosed herein. 
     In another aspect, a method for adjusting track width of a truck axle comprises cutting off at least a portion of a pre-existing spindle associated with a truck axle housing at a point between an axle flange and an outboard end of the pre-existing spindle to define a retained spindle segment. The method further comprises aligning an axle extension member with the retained spindle segment, wherein the axle extension member comprises an annular spacer portion comprising an end face defining an inboard end of the axle extension member, a spindle portion extending from the annular spacer portion and defining an outboard end of the axle extension member, a first internal bore defined in the annular spacer portion, and a second internal bore defined in the spindle portion and being aligned with the first internal bore along a central axis. The method further comprises receiving the retained spindle segment within the first internal bore. The method further comprises affixing the annular spacer portion to the axle flange. 
     In certain embodiments, the method further comprises removing a pre-existing axle shaft from at least a portion of the pre-existing spindle, and inserting an extended length axle shaft through the first internal bore and the second internal bore. 
     In certain embodiments, said affixing of the annular spacer portion to the axle flange comprises use of a plurality of bolts received by (i) a plurality of circumferentially spaced apertures defined in the annular spacer portion and extending through the end face in a direction substantially parallel to the central axis, and (ii) a plurality of circumferentially spaced holes defined in the axle flange. 
     In certain embodiments, said affixing of the annular spacer portion to the axle flange comprises welding at least a portion of the annular spacer portion to the axle flange. 
     In certain embodiments, a wall of the annular spacer portion defines a plurality of radially extending holes, and the method further comprises threading a plurality of set screws through the plurality of radially extending holes to press against an outer surface of the retained spindle segment. 
     In certain embodiments, prior to the cutting off of the at least a portion of the pre-existing spindle, the outboard end of the pre-existing spindle was a first distance from the axle flange, and by affixing the annular spacer portion to the axle flange, the outboard end of the axle extension member is a second distance from the axle flange, the second distance greater than the first distance. 
     Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. 
         FIG. 1A  is a perspective view of a truck axle housing; 
         FIG. 1B  is a cross-sectional view of a dual tire wheel as received by a truck axle having a standard track configuration, with illustration of a truck load line substantially centered between outer and inner wheel bearings; 
         FIG. 1C  is a cross-sectional view of a super single wheel as received by a truck axle having a standard track configuration, with illustration of an offset truck load line positioned substantially closer to the outer wheel bearing than to the inner wheel bearing; 
         FIG. 2A  is a perspective view of the truck axle housing of  FIGS. 1A-1D , following addition of left and right axle extension members as disclosed herein to adjust an axle track width from a standard track configuration to a wider track configuration; 
         FIG. 2B  is a side elevation view of the axle extension member of  FIG. 2A  mounted to an axle flange of a truck; 
         FIG. 3A  is a perspective view of an axle extension member similar to the axle extension member of  FIGS. 2A and 2B  but with addition of radially extending holes defined through an annular spacer portion; 
         FIG. 3B  is a cross-sectional view of the annular spacer portion of the axle extension member of  FIG. 3A ; 
         FIG. 3C  is a side elevation view of the axle extension member of  FIG. 3A ; 
         FIG. 3D  is a side cross-sectional view of the axle extension member of  FIG. 3C ; 
         FIG. 4A  is a side elevation view of a portion of a housing arm including a pre-existing spindle and indicating a cut line in accord with the invention; 
         FIG. 4B  is a side elevation view of a portion of a housing arm including a retained spindle segment formed by cutting the pre-existing spindle of  FIG. 4A  along the cut line; 
         FIG. 4C  is a side elevation assembly view of the axle extension member of  FIGS. 3A-3D  aligned with the retained spindle segment of  FIG. 4B ; 
         FIG. 4D  is a perspective assembly view of the axle extension member of  FIGS. 3A-3D  aligned with the retained spindle segment of FIG.  4 B, and illustrating a portion of a truck axle housing from which the retained spindle extends; 
         FIG. 4E  is a side elevation view of the axle extension member mounted to an axle flange of the housing arm with the retained spindle segment of  FIG. 4B  disposed in a bore in the axle extension member; 
         FIG. 4F  is a perspective view of the axle extension member mounted to the axle flange of the housing arm with the retained spindle segment of  FIG. 4B  disposed in a bore of the axle extension member following attachment therebetween, illustrating the portion of the truck axle housing to which the retained spindle segment is joined; 
         FIG. 4G  is a cross-sectional view showing the attached axle extension member and the retained spindle segment of  FIG. 4B ; 
         FIG. 4H  is a cross-sectional view showing the attached axle extension member and the retained spindle segment with further illustration of an extended axle arranged within the axle extension member and within the retained spindle segment; 
         FIG. 5A  is a front perspective view of the axle extension member of  FIGS. 3A-3D  attached to a brake mount, with a wheel flange of an axle proximate to an outboard end of the axle extension member; 
         FIG. 5B  is a rear perspective view of the axle extension member and brake mount of  FIG. 5A , with inclusion of the wheel flange; 
         FIG. 5C  is a side elevation view of the axle extension member and brake mount of  FIGS. 5A and 5B , without the wheel flange; and 
         FIG. 5D  is a side elevation view of the axle extension member of  FIGS. 3A-3D  attached to a brake mount according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Details of illustrative embodiments are described hereinafter. 
       FIG. 2A  is a perspective view of a truck axle housing  100 , with left and right axle extension members  200 A,  200 B (referred to generally as axle extension member  200 ) attached thereto to adjust (i.e., increase) an axle track width. The truck axle housing  100  includes a central housing portion  102  from which a left arm  104 A and a right arm  104 B extend, with the right arm  104 B and the left arm  104 A extending from opposite sides of the central housing portion  102  (right and left being relative to the drawing figure). At a distal or outboard end of the left arm  104 A is a left axle flange  106 A, and at a distal end of the right arm  104 B is a right axle flange  106 B. Each of the left and right axle flanges  106 A,  106 B (referred to generally as axle flange  106 ) includes a plurality of circumferentially spaced apertures  108  (e.g., circumferentially spaced holes) for mounting a brake assembly thereto. As explained in more detail below, the left axle extension member  200 A is attached to and extends from a distal end of the left axle flange  106 A, and the right axle extension member  200 B is attached to and extends from a distal end of the right axle flange  106 B. The left and right axle extension members  200 A,  200 B each include a spindle portion  206  that provides supporting surfaces for inner and outer wheel bearings (not shown). A left outboard axle shaft flange  112 A is formed at the end of the axle shaft and extends from an outboard end of the left axle extension member  200 A, and a right axle shaft flange (not shown) extends from an outboard end of the right axle extension member  200 B. The left and right outboard axle shaft flanges  112 A,  112 B (referred to generally as outboard axle shaft flange  112 ) each include a plurality of circumferentially spaced apertures  114  for mounting a wheel thereto. 
       FIG. 2B  is a side elevation view of the axle extension member  200  mounted to the right axle flange  106 B. The axle extension member  200  is configured for attachment to the axle flange  106  of a truck to modify the truck from a standard track configuration to a wider track configuration. The axle extension member  200  includes an inboard end  202 A, an outboard end  202 B opposite the inboard end  202 A, and a central axis B-B extending therethrough. The axle extension member  200  includes an annular spacer portion  204  and a spindle portion  206  with a mating interface  208  therebetween. In certain embodiments, the mating interface  208  is a welded interface. In other embodiments, the annular spacer portion  204  is integrally formed with the spindle portion  206  at the mating interface  208 . 
     The annular spacer portion  204  (which may serve as a spacer disk) includes an end face  210  defining the inboard end  202 A. The end face  210  is configured to abut an outboard face  212  of the left axle flange  106 A (shown in  FIG. 2A ). The spindle portion  206  extends from the annular spacer portion  204  and defines the outboard end  202 B. The spindle portion  206  includes wheel bearing support surfaces  214  configured to receive inner and outer wheel bearings of a hub. Accordingly, the axle extension member  200  is configured to adjust the axle track width and center the load line on an approximate center of the spindle portion  206 , with such load line being generally equidistant between the inner and outer wheel bearings (not shown) supportable on the spindle portion  206 . As explained in more detail below, the annular spacer portion  204  defines a first internal bore, and the spindle portion  206  defines a second internal bore aligned with the first internal bore along the central axis B-B. The first and second internal bores are configured to receive an extended length axle shaft. 
       FIGS. 3A-3D  illustrate an axle extension member  200 ′ that is similar to the axle extension member  200  of  FIGS. 2A and 2B  but with the addition of a plurality of radially extending holes  310  defined through the annular spacer portion  204 . The axle extension member  200 ′ includes an inboard end  202 A, an outboard end  202 B opposite the inboard end  202 A, and a central axis B-B extending therethrough. The axle extension member  200 ′ includes an annular spacer portion  204  and a spindle portion  206  with a mating interface  208  therebetween. Referring to  FIGS. 3A, 3C, and 3D , the annular spacer portion  204  includes a peripheral wall  300  defining an end face  210 . As illustrated, the peripheral wall  300  is generally cylindrical. It is conceivable that a peripheral wall could be provided in other shapes in alternative embodiments. The peripheral wall  300  defines a first internal surface  302  defining a first internal bore  304 , and defines a first external surface  306 . As explained in more detail below, the first internal bore  304  is configured to receive a portion of an extended length axle shaft of an extended truck axle therethrough. Further, the first internal bore  304  may be configured to receive a portion of the pre-existing spindle  110 , as also explained in more detail below. The peripheral wall  300  is generally sized and configured to be the same, similar, and/or complementary to the size of the axle flange  106 . 
     Referring to  FIG. 3B , the peripheral wall  300  further includes a plurality of circumferentially spaced apertures  308 . Each circumferentially spaced aperture  308  has an axis parallel with the central axis B-B of the axle extension member  200 ′. Each circumferentially spaced aperture  308  extends through a thickness of the annular spacer portion  204 . The plurality of circumferentially spaced apertures  308  is configured to receive fasteners (e.g., bolts) therethrough to attach the annular spacer portion  204  of the axle extension member  200 ′ to the axle flange  106  of the truck axle housing  100 . The peripheral wall  300  further defines a plurality of radially extending holes  310 . The radially extending holes  310  extend from the first external surface  306  to the first internal surface  302  in a direction perpendicular to the central axis B-B. The plurality of radially extending holes  310  is configured to receive fasteners (e.g., screws) therethrough to promote positioning and/or attachment between the annular spacer portion  204  and a retained spindle portion (described in more detail below). 
     Referring to  FIGS. 3A, 3C, and 3D , the spindle portion  206  includes a peripheral wall  312  defining an end face  314 . The peripheral wall  312  is generally cylindrical, but could be of any other shape. The peripheral wall  312  defines a second internal surface  316  (shown in  FIG. 3D ) defining a second internal bore  318 , and defines a second external surface  320 . The second internal bore  318  is configured to receive therethrough a portion of an extended length axle shaft, which is also received by the first internal bore  304  that is aligned with the second internal bore  318  along the central axis B-B. The second external surface  320  includes wheel bearing support surfaces  214  configured to contact and support inner and outer wheel bearings  120 A,  120 B (not shown). In certain embodiments, the wheel bearing support surfaces  214  are configured to receive rotational surfaces of the inner and outer wheel bearings of a hub. When rotational surfaces of the inner and outer wheel bearings are received on the wheel bearing support surfaces  214 , a vertical load center applied on the single hub piloted wheel is substantially centered between the inner and outer wheel bearings. As shown in  FIGS. 3A and 3C , the second external surface  320  further includes a threaded surface  324  positioned proximate to the end face  314  to secure the hub to the spindle portion  206 . 
     In certain embodiments, the spindle portion  206  is sized, shaped, and otherwise configured to be the same or at least similar to the pre-existing spindle  110  (shown in  FIG. 1A ). As may be seen, a length of the spindle portion  206  is greater than a length of the annular spacer portion  204 , and the spindle portion  206  generally has a smaller diameter than the annular spacer portion  204 . Further, referring to  FIG. 3D , the second internal bore  318  may include an inboard segment  319 A and an outboard segment  319 B, where a diameter of the inboard segment  319 A is larger than a diameter of the outboard segment  319 B. In particular, the inboard segment  319 A may be sized and configured to receive a portion of the pre-existing spindle  110 . The inboard and outboard segments  319 A,  319 B may be sized and configured to receive an extended axle shaft therethrough. 
     The axle extension member  200 ′ may be made of various materials. For example, the axle extension member  200 ′ (e.g., annular spacer portion  204  and/or spindle portion  206 ) may be fabricated of forged steel. 
     Steps of a method for adjusting a track width of a truck axle may be understood with reference to  FIGS. 4A-4H . As a preliminary matter, such a method may include removing wheels, hubs, and brakes, and removing a pre-existing axle shaft (not shown) from at least a portion of the pre-existing spindle  110 . Elements not described in conjunction with  FIGS. 4A-4H  are described hereinabove in conjunction with  FIGS. 1A-3D . 
       FIG. 4A  is a side elevation view showing a portion of the housing arm  104 B with a pre-existing spindle  110  prior to cutting off at least a portion of the pre-existing spindle  110  along a cut line  403  to divide the pre-existing spindle  110  into a retained spindle segment  400  and a discarded spindle segment  402 . As illustrated, the method includes cutting off at least a portion of the pre-existing spindle  110  associated with the truck axle housing  100  (shown in  FIG. 1A ) along a cut line located at a point between a (right) inboard axle flange  106 B and an outboard end  405  of the pre-existing spindle  110 . Cutting the pre-existing spindle  110  defines a retained spindle segment  400  (having an outer wall  404 ) extending from the housing arm and a discarded spindle segment  402  which is subsequently removed from the retained spindle segment  400 . It is noted that prior to cutting of the pre-existing spindle  110 , the outboard end  405  of the pre-existing spindle  110  had a first length Li from the inboard axle flange  106 B. One benefit of retaining a portion of the pre-existing spindle  110  as the retained spindle segment  400  is that the portion provides a mating surface against which an inner surface of an axle extension member may be engaged, thereby promoting secure attachment (e.g., in combination with a bolted or welded connection between an axle extension member and the axle flange  106 B). In certain embodiments, however, the entire pre-existing spindle  110  may be removed. 
       FIG. 4B  is a side elevation view of a portion of the housing arm  104 B with the retained spindle segment  400  following cutting of the pre-existing spindle  110  along the cut line  403 . 
     Referring to  FIGS. 4C and 4D , the method further includes aligning a (right) axle extension member  200 B′ with the retained spindle segment  400 . As disclosed previously herein with regard to similar axle extension members  200 ,  200 ′, the axle extension member  200 B′ includes an annular spacer portion  204  (with an end face  210  defining the inboard end  202 A), as well as a spindle portion  206  that extends from the annular spacer portion  204 . The spindle portion  206  defines an outboard end  202 B. The axle extension member  200 B′ defines a first internal bore  304  (shown in  FIGS. 3D and 4G ) in the annular spacer portion  204 , and defines a second internal bore  318  (shown in  FIGS. 3D and 4G ) in the spindle portion  206 . The second internal bore  318  is aligned with the first internal bore  304  along the central axis B-B. The plurality of circumferentially spaced apertures  308  of the annular spacer portion  204  is aligned with the plurality of circumferentially spaced apertures  108  of the axle flange  106 B to accommodate bolts or other fasteners (not shown). 
       FIGS. 4E and 4F  show the axle extension member  200 B′ mounted to the axle flange  106 B, the retained spindle segment  400  (shown in  FIG. 4C ) being disposed in a bore in the axle extension member. In preparation for such attachment, the retained spindle segment  400  is received within the first internal bore  304 . In particular, the end face  210  of the annular spacer portion  204  contacts the outboard face  212  of the axle flange  106 B, with the first internal bore  304  preferably being sized and shaped to contact the outer wall  404  (shown in  FIGS. 4A-4C ) of the retained spindle segment  400  received therein. In addition, the holes  108  in the axle flange  106 B are aligned with the apertures  308  in the annular spacer portion  204 , and the method may include affixing the annular spacer portion  204  to the axle flange  106 B. As described above, the peripheral wall  300  of the annular spacer portion  204  defines a plurality of radially extending holes  310 . In certain embodiments, the method further includes threading a plurality of set screws (not shown) or other fasteners through the plurality of radially extending holes  310  to press against an outer wall  404  of the retained spindle segment  400 . In certain embodiments, the set screws (or other fasteners) may be temporarily or permanently attached. If permanently attached, the set screws (or other fasteners) may provide structural support between the axle extension member  200 B′ and the retained spindle segment  400 . 
     In certain embodiments, primary attachment between the annular spacer portion  204  and the axle flange  106 B may be made with bolts or other fasteners. For example, an attachment method may include use of a plurality of bolts received by the plurality of circumferentially spaced apertures  308  defined in the annular spacer portion  204  and extending through the end face  210  in a direction substantially parallel to the central axis B-B and the plurality of circumferentially spaced apertures  108  defined in the axle flange  106 B. Such a configuration causes the peripheral wall  300  of the annular spacer portion  204  of the axle extension member  200 B′ to fit over the retained spindle segment  400 . In certain embodiments, the size and configuration of the first internal surface  302  (shown in  FIGS. 4G and 4H ) is about the same size and shape as the outer wall  404  of the retained spindle segment  400 . In this way, the retained spindle segment  400  helps supports the axle extension member  200 B′. In certain embodiments, as discussed above, the retained spindle segment  400  may be omitted, and the axle extension member  200 B′ may be supported only by fasteners attaching the axle extension member  200 B′ to the inboard axle flange  106 B. 
     In certain embodiments, the first internal surface  302  of the annular spacer portion  204  may be threaded and configured to threadably engage the retained spindle segment  400 , or may be configured to frictionally engage the retained spindle segment  400  (e.g., via an interference fit that may be accomplished by thermal expansion of the annular spacer portion  204  before fitting around the retained spindle segment  400 ). When non-permanent attachment is made between the annular spacer portion  204  and the retained spindle segment  400 , the truck could easily be reconfigured for a standard axle width by removing the axle extension member  200 B′ and replacing it with a standard track width axle housing member. Alternatively, or additionally, the method may include welding at least a portion of the annular spacer portion  204  to the axle flange  106 B. 
     Referring to  FIG. 4E , by affixing the annular spacer portion  204  to the axle flange  106 B, the outboard end  202 B of the axle extension member  200 B′ is a second length L 2  from the axle flange  106 B, and the second length L 2  is greater than the first length Li shown in  FIG. 4A . In various embodiments, the annular spacer portion  204  may provide for an extension of any desired length, such as between 1 and 12 inches (e.g., 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, etc.) or between 25.4 mm and 304.8 mm (e.g., 25.4 mm, 50.8 mm, 76.2 mm, 101.6 mm, 127 mm, etc.). 
       FIG. 4G  is a cross-sectional view of the attached axle extension member  200 B′ and the retained spindle segment  400  of  FIG. 4E . As shown in  FIG. 4G  and  FIG. 4H , the retained spindle segment  400  defines an internal bore  124  to accommodate passage of an axle (as shown in  FIG. 4H ). 
     Referring to  FIG. 4H , the method further includes inserting an extended length axle shaft  408  of an extended length truck axle  406  (e.g., medium or wide axle) through the first internal bore  304  and the second internal bore  318  of the axle extension member  200 B′. It is noted that the retained spindle segment  400  is also received by the first internal bore  304 , such that a portion of the extended length axle shaft  408  further extends through the internal bore  124  defined by the retained spindle segment  400 . Accordingly, in this way, the entire truck axle housing  100  (shown in  FIGS. 1A, 2A, 4D, and 4F ) does not need to be replaced. The brakes and bearings can be reinstalled as well. 
     Axle extension members disclosed herein beneficially reduce the time, cost, and complexity of adjusting (e.g., increasing) the axle track width to enable trucks already equipped with standard track rear axles and dual tire wheels to be equipped with super single wheels and tires. 
       FIGS. 5A-5C  illustrate axle extension members  200 ′ with associated brake mounts  500 ,  500 ′. It is noted that when converting from dual tires to super single tires as described herein, truck operators may also desire to convert from drum brakes to air disc brakes. Utilization of a brake mount integrated or otherwise coupled with an axle extension member  200 ′ may provide a mechanism for mounting the air disc brakes to the axle extension member  200 ′. Elements not described with regard to  FIGS. 5A-5C  are described hereinabove with regard to  FIGS. 1A-4H . 
     Referring to  FIGS. 5A and 5B , a brake mount  500  includes a center hole  504  defined by a central body portion  506 . A top portion  508  of the brake mount  500  extends upward from the central body portion  506 , and a bottom portion  510  of the brake mount  500  extends downward from the central body portion  506  in a direction opposing the top portion  508 . In certain embodiments, the annular spacer portion  204  of the axle extension member  200 ′ is inserted into the center hole  504  of the brake mount  500 . In this way, the first external surface  306  of the peripheral wall  300  of the annular spacer portion  204  includes a brake mounting region  502  (shown in  FIG. 5C ). In certain embodiments, the brake mounting region  502  may be attached to an outer perimeter of the annular spacer portion  204  by welding; alternatively, the brake mount  500  may be integrally formed with the annular spacer portion  204 . Further, an outboard axle flange  112  is attached to the spindle portion  206  of the axle extension member  200 ′, as described above. 
       FIG. 5C  is a side elevation view of the axle extension member  200 ′ and brake mount  500  of  FIGS. 5A and 5B , without the wheel flange  112 . 
     Referring to  FIG. 5D , in another embodiment, a brake mount  500 ′ may be attached at a brake mounting region  502 ′ along a face of the annular spacer portion  204  of an axle extension member  200 ′. In particular, at least a portion of the spindle portion  206  is received in a center hole  504  of the brake mount  500 ′ proximate to a mating interface  208  between the annular spacer portion  204  and the spindle portion  206 . Accordingly, attachment of the brake mount  500 ′ to the axle extension member  200 ′ is positioned outboard relative to the attachment shown in  FIG. 5C . As a result, the brake mount  500 ′ may include top and bottom portions  508 ,  510  that are offset in an inboard direction relative to a central body portion  506  of the brake mount  500 ′. In this manner, when the brake mount  500 ′ is attached to the axle extension member  200 ′, the top portion  508  and bottom portion  510  may extend inboard relative to the central body portion  506 . In certain embodiments, the brake mount  500 ′ may receive portions of the same fasteners used to couple the annular spacer portion  204  to an inboard wheel flange. 
     While the invention has been described herein in reference to specific aspects, features, and illustrative embodiments, it will be appreciated that the utility of the invention is not thus limited, but rather extends to and encompasses numerous other variations, modifications and alternative embodiments, as will suggest themselves to those of ordinary skill in the field of the present invention, based on the disclosure herein. Various combinations and sub-combinations of the structures described herein are contemplated and will be apparent to a skilled person having knowledge of this disclosure. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein. Correspondingly, the invention as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its scope and including equivalents of the claims.