Patent Publication Number: US-2023150305-A1

Title: Trailer axles for wide base tires

Description:
FIELD OF THE INVENTION 
     The subject matter of the present invention relates to axles for trailers utilizing wide base tires. More particularly, the present application involves forward and rearward axles on a trailer of a tractor trailer that have mounting portions that are angled relative to the lateral direction so that wear is improved on wide base tires mounted to the axles. 
     BACKGROUND OF THE INVENTION 
     Tractor trailers include a tractor that hauls a trailer filled with cargo. The trailer and drive tires of tractor trailers have tire positions that are outfitted with dual tires which are two tires side by side at that particular wheel end position. The steer tires at the front of the tractor are single width tires. It is known to replace the dual tires of the tractor and trailer with single wide base tires. In this regard, the two side by side tires are replaced with a single wide base tire that itself can handle the loading demands of the two side by side tires. The use of single wide base tires instead of dual tires can reduce fuel consumption of the tractor trailer because the rolling resistance generated by the two sidewalls of the single wide base tire is less than the rolling resistance generated by the four sidewalls of the dual tires. Also, the use of single wide base tires instead of duals reduces the overall weight of the wheel/tire assemblies of the tractor trailer which means more cargo can be moved on each trip the tractor trailer takes. Further, since extra tires from the dual sets are eliminated time and labor will be saved because the tractor trailer will have fewer tires to mount, demount, and pressure check. Experience has shown that single wide base tires may come out of service because of irregular (sometimes characterized as asymmetric) wear. A wide base tire that experiences irregular wear may have more tread wear near a shoulder of the tire and less tread wear at the center or opposite shoulder. This tire may be removed from service, although it could have lasted many more miles if the tread wear was more even over the entire width of the tread. Although the construction of wide base tires themselves has been modified to reduce the problem of irregular wear, it still remains the case that tires may have to come out of service early as a result of this issue. As such, there remains room for variation and improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG.  1    is a perspective view of a wide base tire with a portion cut away to show various layers of the wide base tire. 
         FIG.  2    is a side view of a tractor trailer. 
         FIG.  3    is a top view of the tractor trailer of  FIG.  2   . 
         FIG.  4    is a back view of a tractor trailer. 
         FIG.  5    is a back view of a forward axle of a trailer that has first and second wide base tires. 
         FIG.  6    is a back view of a rearward axle of a trailer that has third and fourth wide base tires. 
         FIG.  7    is a back view of a rearward axle of a trailer that has third and fourth wide base tires in accordance with another exemplary embodiment. 
     
    
    
     The use of identical or similar reference numerals in different figures denotes identical or similar features. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. 
     The present invention provides for an apparatus  10  for a trailer  48  of a tractor trailer  44  that includes forward and rearward axles  12 ,  28  that carry wide base tires  24 ,  26 ,  40  and  42 . The axles  12 ,  28  have mounting portions  16 ,  20 ,  32 ,  36  that are angled  56   58 ,  60 ,  62  with respect to the lateral direction  52 . The angles  56 ,  58 ,  60 ,  62  are provided by the axles  12  and  28  and angle the wide base tires  24 ,  26 ,  40  and  42  so that the individual tires each wear more evenly to reduce irregular wear among them all. This reduction in irregular wear extends the life of the wide base tires  24 ,  26 ,  40  and  42  of the trailer  48 . 
     A wide base tire  66  as shown in  FIG.  1    is a truck tire that is capable of handling the load of two single truck tires commonly referred to as duals. The wide base tire  66  differs from duals in that this type of tire normally includes an extra reinforcing layer that strengthens and helps shape the tire  66  and thus allows the tire to be made wider and carry more loading. The wide base tire  66  shown in  FIG.  1    is a MICHELIN® X ONE® tire provided by Michelin North America, Inc. having offices located at 1 Parkway South, Greenville, S.C., USA. The wide base tire  66  has a circumferential direction  68  that extends around an axis of the wide base tire  66  and thus extends in the direction of rotation of the tire  66 , and a radial direction  70  that extends in the radial direction from this axis and is the direction from the inner liner of the tire  66  to the tread of the tire  66 . The wide base tire  66  has a radial ply  82  that extends between the two beads of the tire  66 . A full-width protector belt ply  80  is located radially outward from the radial ply  82 . A first bias ply  72  is located outward from the full-width protector belt ply  80  in the radial direction  70  and includes cords that lay diagonally across the tire  66  so that they do not run completely in the circumferential direction  68 . The belt package next includes the circumferential belt layer  76  that is outboard in the radial direction  70  from the first bias ply  72  and has cords that are angled at near 0 degrees to the circumferential direction  68  so that the cords extend completely in the circumferential direction. The inclusion of the circumferential belt layer  76  provides strength to the tire  66  to allow it to handle the extra loading and have the wider footprint indicative of a wide base tire. 
     The second bias ply  74  is located outward from the circumferential belt layer  76  in the radial direction  70  and has cords that are diagonal to the circumferential direction  68  so that they lay opposite in direction to those of the first bias ply  72 . In this regard, the magnitudes of the angles the cords of the bias plies  72 ,  74  lay relative to the circumferential direction  76  are approximately the same, but their directions are opposite. The circumferential belt layer  76  is thus between two bias plies  72 ,  74  that has oppositely disposed cords. A third bias ply  78  is located outward from the second bias ply  74  in the radial direction  70  and has cords that lay diagonally relative to the circumferential direction  68  and can be in the same direction and could have the same magnitude as those of the second bias ply  74 . Tread of the tire  66  may be located outboard from the third bias ply  78  in the radial direction  70 , and the various layers  72 ,  74 ,  76 ,  78 ,  80 ,  82  make up a six-ply package to handle the extra loading required of a wide base tire  66 . 
     The circumferential belt layer  76  tends to negate the effect of the first bias ply  72  pulling the tire  66  because the circumferential belt layer  76  is located outward from the first bias ply  72  in the radial direction  70 . However, the second bias ply  74  is outward from the circumferential belt layer  76  and the directional force-generating effect of its biasing is not canceled by the circumferential belt layer  76 . As a result, the tire  66  will exhibit ply steer in that the tire  66  will exhibit a lateral pulling force when in motion so as to move perpendicular to the radial direction  70 . This lateral pulling force is leftward relative to the travel path of the vehicle. The third bias ply  78  has cords angled in the same direction as those of the second bias ply  74  and thus does not counteract the biasing forces. The wide base tire  66  used may be a ply steer tire  66  in that it pulls to one side in the lateral direction upon travel due to the construction of the belt package with the aforementioned plies  72 ,  74 ,  76 ,  78 ,  80 ,  82 . This direction of travel exhibited by all of the MICHELIN® X ONE  0  wide base tires  66  on the trailer  48 , and in some cases any wide base tire  66  on the trailer  48  and tractor  46  causes the tractor trailer  44  to want to pull to the middle of the road. Other types of wide base tires are known that do not include very much if any ply steer in that the bias plies are inward of the circumferential belt layer in the radial direction  70  so that any ply steer contribution by these bias plies is canceled out (or minimized) by the presence of the circumferential belt layer or some other technology. 
       FIGS.  2  and  3    show a tractor trailer  44  that includes a tractor  46  that is attached to the trailer  48  and hauls the trailer  48  and cargo located therein. The tractor trailer unit  44  is sometimes referred to as a semi-trailer truck, a tractor trailer, an eighteen wheeler, a transport truck, or by other names. The tractor trailer  44  includes tires that are all heavy duty truck tires. In this regard, the tires described herein are not designed for nor used with a car, motorcycle, or light truck (payload capacity less than 4,000 pounds), but are instead designed for and used with heavy duty trucks such as 18 wheelers, garbage trucks, or box trucks. As such, in some embodiments the trailer  48  has a payload capacity of 4,000 pounds or greater. The tractor trailer unit  44  can include a single trailer  48  or the tractor trailer unit  44  may have two or three trailers  48  in other embodiments. The trailer  48  has a longitudinal direction  50  that is the forward and rearward directions of travel of the tractor trailer  44 . The lateral direction  52  is the width direction of the trailer  48 , and the vertical direction  54  of the trailer  48  is the up down direction of the trailer  48  relative to the ground  84  onto which the trailer  48  rests. The trailer  48  has a centerline  64  that goes through the middle of the trailer  48  in the lateral direction  52  such that half of the trailer  48  is on the left hand side of the centerline  64  and the other half is on the right hand side of the centerline  64 . 
     The tractor  46  has a pair of steer tires  94 ,  96  located at its forward end in the longitudinal direction  50 . The tractor  46  also has four drive tires  86 ,  88 ,  90  and  92  that transfer power from the engine to cause the tractor  46  to move. Other tractor  46  designs are known in which only one of the axles is a drive axle and the other is not a drive axle, and yet other tractor  46  designs are known in which but a single axle is at the back of the tractor  46  and it is a driven axle. The drive tires  86 ,  88 ,  90  and  92  are each wide base tires and not dual tires, but in other embodiments some or all of the drive tires  86 ,  88 ,  90  and  92  may be duals instead of wide base tires. The trailer  48  has a bogie assembly  10  that may include the forward axle  12  and rearward axle  28  in which the forward axle  12  is forward of the rearward axle  28  in the longitudinal direction  50 . The forward axle  12  has first and second wide base tires  24 ,  26  and the rearward axle  28  has third and fourth wide base tires  40 ,  42 . Although shown as having less than 18 tires, the tractor trailer  44  may still be referred to as an 18 wheeler since this term refers to vehicles of this type and configuration. The first wide base tire  24  occupies the forward left position on the trailer  48  and the second wide base tire  26  is at the forward right position. The third wide base tire  40  is at the back left position, and the fourth wide base tire  42  is at the back right position of the trailer  48 . 
     The forward axle  12  and rearward axle  28  may be part of a bogie assembly. Also, the axles  12  and  28  can be part of a conventional tandem axle suspension system. The axles  12  and  28  can be spaced apart 4 feet from one another in the longitudinal direction  50 . The apparatus  10  is not designed for use with the stated angles  56 ,  58 ,  60 ,  62  in which the axles  12  and  28  are spaced ten feet apart in the longitudinal direction  50 . Axles that are spaced 10 feet apart in the longitudinal direction  50  are known as “spread axle tandems” and the present apparatus  10  does not incorporate these types of axles  12 ,  28 . Instead, the axles  12 ,  28  used in the present apparatus  10  are spaced much closer to one another in the longitudinal direction  50  such as around being 4 feet. 
     A back view of the trailer  48  is shown with reference to  FIG.  4   . The rearward axle  28  is shown and the forward axle  12  is obscured from sight due to the rearward axle  28 . The rearward axle  28  is attached to the bottom of the trailer  48  and has a suspension system associated therewith to reduce impact forces on the trailer  48 . The rearward axle  28  carries the third and fourth wide base tires  40  and  42  and is angled such that the entire rearward axle  28  is not parallel to the ground  84 . Instead, one or both of the ends of the rearward axle  28  are angled relative to the ground  84  such that both of the wide base tires  40  and  42  are not positioned with their axes parallel to the ground but instead one or more are angled relative thereto. Tires that do not have their axes parallel to the surface of the ground introduce camber into the vehicle which can cause the vehicle to pull to the side that has positive camber. Tires that have their axes parallel to the ground are said to have neutral camber. It is to be understood that some road surfaces are angled to allow water to drain therefrom, or because of the bank of the road. As such, when described as being vertical or angled relative to the lateral direction its to be understood that this reference is to the surface of the roadway/ground  84  that the vehicle rests upon and not necessarily to a completely vertical direction from the center of the earth upwards. For the purposes of discussion herein, we presume the “ground”  84  to be level and flat and not angled, crowned or curved. However, if the ground  84  is so in some instances the angles described are relative to this angled, crowned, or curved ground  84 . The lateral direction  52  may be perpendicular to a surface normal extending from the ground  84 , and in this regard the lateral direction  52  may be said to be parallel to the ground  84  and not at an angle to the ground  84 . 
       FIG.  5    is a rear view of the forward axle  12  of the trailer  48  looking from behind the forward axle  12  forward in the longitudinal direction  50 . The forward axle  12  has a forward central body  14  through which the centerline  64  passes. The forward axle  12  may have a central axis that is parallel to the lateral direction  52 . Outboard in the lateral direction  52  may be described with reference to the centerline  64  as being on one side of the trailer  48  and moving away from the centerline  64  in the lateral direction  52 . Inboard in the lateral direction  52  may be described as moving toward the centerline  64  in the lateral direction  52  when viewed from one of the two sides of the trailer  48  in the lateral direction  52 . A first forward mounting portion  16  extends from the forward central body  14 , and the first wide base tire  24  is rotatably mounted to the first forward mounting portion  16 . A hub, brakes and other components can be included as well but are not shown for sake of clarity. The first forward mounting portion  16  is angled relative to the ground  84  in the lateral direction  52 , and is likewise angled relative to the forward central body  14 . In this regard, the first forward mounting portion  16  has a component of extension downward in the vertical direction  54  upon extension away from the forward central body  14  outboard in the lateral direction  52 . The first forward mounting portion  16  has a first forward mounting portion axis  18  that is oriented at an angle  56  to the lateral direction  52 . The axis  18  extends through the center of the first forward mounting portion  16  which can be cylindrical, square, rectangular or have any cross-sectional shape. The angle  56  may be +0.75 to +0.95 degrees in some embodiments. In other embodiments, the angle  56  is +0.80 to +0.90 degrees, and in yet other embodiments the angle  56  is +0.85 degrees. The magnitude of the angle  56  is exaggerated in  FIG.  5    and is not drawn to scale. This angle  56  is measured when the forward axle  12  is produced such that the weight of the trailer  48  is not loaded onto the forward axle  12 . When the trailer  48  is fully loaded, this weight will push down onto the center of the forward axle  12  and cause it to bend which will in turn cause the tires  24  and  26  to bend so they have a lower camber angle and possibly even a negative camber angle. The angle  56  is set into the forward axle  12  before any loading is put onto the trailer  48 , but is to be understood that when loading is applied to the trailer  48  that this will distort the angle  56  originally imparted into the forward axle  12 . 
     The second forward mounting portion  20  extends outboard from the forward central body  14  in the lateral direction  52  and has a second forward mounting portion axis  22  that is located in the center of the second forward mounting portion  20 . The second forward mounting portion  20  could have a circular, square, or rectangular cross-sectional shape. The second forward mounting portion  20  has a component of extension towards the ground  84  upon extending outboard in the lateral direction  52  from the forward central body  14 . An angle  58  is defined between the second forward mounting portion axis  22  and the lateral direction  52 . The angle  58  may be +0.08 to +0.28 degrees in some embodiments. In other embodiments, the angle  58  is +0.13 to +0.23 degrees and in other embodiments the angle  58  is +0.18 degrees. The angle  58  is set into the forward axle  12  before any loading is put onto the forward axle  12  such as by loading the trailer  48  onto which the forward axle  12  is mounted. 
     The first and second wide base tires  24 ,  26  are provided with positive camber via the angles  56 ,  58 . In this regard, the tires  24 ,  26  are both angled relative to the ground  84  and extend outboard in the lateral direction  52  upon their extension upwards in the vertical direction  54  from the ground  84 . The tops of the tires  24 ,  26  are located farther outboard in the lateral direction  52  than the bottoms of the tires  24 ,  26 . 
     The rearward axle  28  is shown in  FIG.  6    which is a view from behind the rearward axle  28  looking forward in the longitudinal direction  50  of the trailer  48 . The rearward axle  28  has a rearward central body  30  through which the centerline  64  is disposed. First and second rearward mounting portions  32  and  36  extend from opposite lateral ends of the rearward central body  30 . The first rearward mounting portion  32  has a first rearward mounting portion axis  34  located in its center, and the second rearward mounting portion  36  has a second rearward mounting portion axis  38  located at its center. The mounting portions  32 ,  36  may have circular, rectangular, square, triangular, or irregular cross-sectional shapes and can be variously shaped in accordance with different exemplary embodiments. 
     Both of the first and second rearward mounting portion axes  34  and  38  extend downward in the vertical direction  54  upon their extension outboard in the lateral direction  52  from the rearward central body  30 . An angle  60  is established between the first rearward mounting portion axis  34  and the lateral direction  52 , and an angle  62  is established between the second rearward mounting portion axis  38  and the lateral direction  52 . The third wide base tire  40  is located on the first rearward mounting portion  32 , and the fourth wide base tire  42  is located on the second rearward mounting portion  36 . The first rearward mounting portion  32  and the third wide base tire  40  occupy the back left tire position of the trailer  46 , and the second rearward mounting portion  36  and fourth wide base tire  42  occupy the back right tire position of the trailer  48 . 
     The angle  60  of the first rearward mounting portion axis  34  can be +0.65 to +0.85 degrees. In other embodiments, the angle  60  is +0.70 to +0.80 degrees, and in other embodiments the angle  60  is +0.75 degrees. The angle  62  between the second rearward mounting portion axis  38  and the lateral direction  52  can be from −0.05 to +015 degrees. In other embodiments the angle  62  is +0.00 to +0.10 degrees, and in other embodiments the angle  62  is +0.05 degrees. It is be understood that if the angle  62  is +0.00 degrees then the second rearward mounting portion axis  38  is parallel to the lateral direction  52 . If the angle  62  is negative, then the second rearward mounting portion axis  38  has a component of extension upwards in the vertical direction  54  upon extension outboard in the lateral direction  52  from the rearward central body  30 . The third and fourth wide base tires  40  and  42  can be angled relative to the lateral direction  52  via solely the angles  60  and  62 , and when both of the angles  60  and  62  are positive the tires  40  and  42  can be said to have positive camber. The angles  60  and  62  shown in  FIG.  6    are not to scale but are exaggerated for purposes of explanation. 
       FIG.  7    shows an alternate embodiment, also not to scale, of the apparatus  10  and in particular the rearward axle  28 . The view is from behind the rearward central body  30  looking forward in the longitudinal direction  50 . The angle  60  and the angle  62  are both negative angles in this embodiment and the tires  40  and  42  have negative camber. As explained, negative angles  60  and  62  cause the axes  34  and  38  to have a component of extension upward in the vertical direction  54  away from the ground  84  as they extend outboard in the lateral direction  52  from the rearward central body  30 . 
     The angles  56 ,  58 ,  60  and  62  are shown as causing the tires  24 ,  26 ,  40  and  42  to be oriented at the same angle magnitude they are oriented at relative to the ground  84 . In this regard camber sleeves, hubs, and other components do not adjust the angle of the tires  24 ,  26 ,  40  and  42  to the ground  84  or lateral direction  52 . Instead, all of the angular orientation of the tires  24 ,  26 ,  40  and  42  is supplied via the angular orientation of the axes  18 ,  22 ,  34  and  38  relative to the lateral direction  52 . As such, embodiments exist in which sleeves to adjust the angle of the tires are not present on the forward axle  12  and rearward axle  28 . In some instances, all of the tires  24 ,  26 ,  40  and  42  are angled relative to the ground  84  so that the bottoms of the tires  24 ,  26 ,  40 ,  42  are inboard in the lateral direction  52  relative to the tops of the tires  24 ,  26 ,  40 ,  42  as defined by the vertical direction  54 . The forward and rearward axles  12 ,  28  can be arranged so that only the four tires  24 ,  26 ,  40 ,  42  are carried by the axles  12  and  28  and no other tires are on the axles  12  and  28 . The apparatus  10  is associated only with the trailer  48  and not the tractor  46 . The apparatus  10  can be for use with a high ply steer tire  66 . In this regard the tires  24 ,  26 ,  40 ,  42  are high ply steer tires that pull one way in the lateral direction  52  during driving. In some instances all of the tires  24 ,  26 ,  40 ,  42  pull in the lateral direction  52  towards the center of the road as the trailer  48  is driven in the right hand lane of the road. 
     The mounting portions  16 ,  20 ,  32 ,  36  are shown as being angled upon their initial extension from the central bodies  14 ,  30  and keeping the same angle  56 ,  58 ,  60 ,  62  along their entire lengths from the central bodies  14 ,  30  to their terminal ends. However, the angles  56 ,  58 ,  60 ,  62  may be located on only a portion of the length of the mounting portions  16 ,  20 ,  32 ,  36  in which other parts or lengths of the mounting portions  16 ,  20 ,  32 ,  36  do not exhibit the angles  56 ,  58 ,  60 ,  62  but are angled different amounts from those shown. 
     The forward and rearward axles  12 ,  28  can be made by forming a hollow tube with solid ends so that the hollow tube makes up the forward and rearward central bodies  14 ,  30 . Brackets could be welded onto the solid ends to form the mounting portions  16 ,  20 ,  32 ,  36 . The angles  56 ,  58 ,  60 ,  62  could be formed in a variety of manners into the axles  12 ,  28 . For example, one manner of manufacture could be bending of the axles  12 ,  28  after they are formed. Additionally or alternatively, the axles  12 ,  28  could be distorted with welding or heating to form the angles  56 ,  58 ,  60 ,  62 . Still further, the angles  56 ,  58 ,  60 ,  62  could be formed by machining in other embodiments. It is to be understood that the angles  56 ,  58 ,  60 ,  62  could be imparted into the axles  12 ,  28  in a variety of manners in other embodiments. The axles  12 ,  28  include their angles  56 ,  58 ,  60 ,  62  from being formed with the angles  56 ,  58 ,  60 ,  62  and not through a subsequent, add-on sleeve or other component added onto the axles  12 ,  28  after their manufacture and placement onto a trailer  48 . 
     The angles  56 ,  58 ,  60 ,  62  are specific to their particular wheel position and have been optimized by applicant in order to result in wide base tires  24 ,  26 ,  40 ,  42  in those positions that have irregular wear properties reduced as much as possible. Why a specific wheel position of the tire  24 ,  26 ,  40 ,  42  would have a specific angle  56 ,  58 ,  60 ,  62  is not an obvious matter of design. There are many interactions between the road surface, slope of the road, the type of suspension of the trailer  48  and its design characteristics, the compliance of the axles  12  and  28 , the camber thrust of the tires, the ply steer of the tires, traffic lane rules, road intersection and interstate exit/entrance layout, and human driver characteristics that all add up to result in the particular wear patterns seen on the differently positioned wide base tires  24 ,  26 ,  40 ,  42 . Applicant theorizes that the different wheel positions will require a different camber angle  56 ,  58 ,  60 ,  62  because each wheel position experiences its own unique wear pattern. As an example, when the tractor trailer  44  makes a tight right hand turn at low speeds in an intersection the left rear tire, in our case the third wide base tire  40 , experiences more wear than the rest of the trailer  48  tires  24 ,  26 ,  42 . The vast majority of the interstate exits require hard right hand turns at fast speeds and these turns likewise are harder on the third wide base tire  40  at the left rear position of the trailer  48 . When making a left hand turn through an intersection, the tractor trailer  44  executes this turn at higher speeds and in a wider manner that is more damaging to the right rear trailer  48  tire which in our case is the fourth wide base tire  42 . Usually when a driver backs up a tractor trailer  44 , the driver nearly always tends to want to do so by turning the tractor  46  to the left relative to the trailer  48  to avoid a blind spot. This method of backing up puts greater wear on the right front trailer tire which is our described second wide base tire  26 . Additionally, the use of a high ply steer tire such as those previously described with reference to the tire of  FIG.  1    introduces even more irregular wear into the equation and this irregular wear may not be evenly distributed to all four tire  26 ,  28 ,  40 ,  42  positions due to these positions themselves experiencing more or less irregular wear. 
     Experiments Carried Out in Accordance with Various Embodiments of the Invention 
     Experiments were conducted in accordance with various exemplary embodiments to determine whether the provision of the angles  56 ,  58 ,  60 ,  62  specified will reduce irregular wear of the wide base tires  24 ,  26 ,  40 ,  42 . The trailer  48  used in the experiments included forward and rearward axles  12 ,  28  that were Hendrickson LDA axles supplied by Hendrickson USA, L.L.C. having offices located 800 South Frontage Road, Woodridge, Ill., USA. The tires used were the same and were MICHELIN® X ONE® tires, and in particular X ONE® LET (Line Energy T) tires. These tires have relatively high amounts of ply steer. The positions as noted in the experimental results TABLE 1 below have the forward left tire position being the first wide base tire  24 , the forward right position being the second wide base tire  26 , the rearward left position being the third wide base tire  40 , and the rearward right position being the fourth wide base tire  42 . The tires were run for variously identified miles, some of which were the end of life removal miles of the tire, and then measured for irregular wear. Although irregular wear could be seen on different ones of the tires, for comparison purposes the tread depth and tread feature depth of the tires were measured and provided in the below table. The inside shoulder remaining is the depth of the tread of the tire near the inside shoulder, and the outside shoulder remaining is the depth of the tread of the tire near the outside shoulder of the tire. These are not measurements of the shoulder, but are instead measurements of the tread depth/tread feature depth at different points along the width of the tire one being near the inside shoulder and the other being near the outside shoulder. The measurement of tread depth at these two oppositely disposed locations on the tread in the width direction provides an indication as to whether irregular wear is occurring as one side of the tire may show more wear than the opposite side of the tire. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Inside 
                 Outside 
                   
               
               
                   
                   
                 shoulder 
                 shoulder 
                 Mileage 
               
               
                 Tire 
                 Angle 
                 remaining 
                 remaining 
                 when 
               
               
                 position 
                 (degrees) 
                 (inches) 
                 (inches) 
                 measured 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Forward Left 
                 0 
                  0/32 
                 13/32 
                 127,600 
               
               
                 Forward Left 
                 +0.85 
                  2/32 
                  3/32 
                 191,900 
               
               
                 Forward Left 
                 0 
                  5/32 
                 13/32 
                 109,900 
               
               
                 Forward Left 
                 0 
                  6/32 
                 14/32 
                 102,200 
               
               
                 Forward left 
                 +0.85 
                 10/32 
                  9/32 
                 118,300 
               
               
                 Forward Left 
                 +0.85 
                  8/32 
                  8/32 
                 111,400 
               
               
                 Forward 
                 0 
                  2/32 
                  3/32 
                 137,900 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Forward 
                 +0.18 
                  0/32 
                  0/32 
                 191,900 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Forward 
                 0 
                  6/32 
                  9/32 
                 109,900 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Forward 
                 0 
                  8/32 
                 10/32 
                 102,200 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Forward 
                 +0.18 
                  8/32 
                  8/32 
                 108,400 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Forward 
                 +0.18 
                  7/32 
                  8/32 
                 118,300 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  4/32 
                 14/32 
                 88,400 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.75 
                  0/32 
                  3/32 
                 191,900 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  2/32 
                  9/32 
                 122,600 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  6/32 
                 12/32 
                 102,300 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.75 
                  8/32 
                  8/32 
                 108,400 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.75 
                  8/32 
                  7/32 
                 118,300 
               
               
                 Left 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  0/32 
                  0/32 
                 137,900 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.05 
                  0/32 
                  0/32 
                 191,900 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  3/32 
                  4/32 
                 122,600 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 0 
                  5/32 
                  9/32 
                 98,100 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.05 
                  6/32 
                  8/32 
                 118,300 
               
               
                 Right 
                   
                   
                   
                   
               
               
                 Rearward 
                 +0.05 
                  8/32 
                  9/32 
                 90,200 
               
               
                 Right 
               
               
                   
               
            
           
         
       
     
     The results of the experiments showed that providing the angles  56 ,  58 ,  60 ,  62  as indicated resulted in reduction of irregular wear. It is to be understood that the angles listed are put into the axles  12  and  28  before loading of the axles  12 ,  28  and before weight of the trailer  48  is put onto the axles and before the trailer  48  is loaded with cargo. There could be a tolerance range put into the numbers because manufacturing of the axles  12 ,  28  may not be completely precise in all embodiments. The tolerancing error is plus or minus 0.05 degrees. These numbers and the tolerancing range are disclosed herein. Applicants were surprised that these small changes in camber at different amounts for all four different tire positions resulted in the results achieved in irregular wear reduction. Applicant&#39;s theorize that expansion of the range from that of the base number to plus or minus 0.10 degrees will also result in improved irregular wear reduction but not at much as would be the case if the 0.05 degree tolerance range were respected. The angles  56 ,  58 ,  60 ,  62  that are established can all be different so that none of them are of the same magnitude, although they all may be positive angles. 
     While the present subject matter has been described in detail with respect to specific embodiments and methods thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be apparent.