Bearing seal with polytetrafluoroethylene thrust bumper

1. A bearing seal, comprising:

a seal case affixable to a hub assembly of a wheel end encircling a rotation axis of the bearing seal;

a sleeve affixable to an axle of the wheel end; and

a thrust bumper disposed between the seal case and the sleeve, the thrust bumper having an initial axial thickness that defines a spacing between the seal case and the sleeve when the seal case and the sleeve are compressed together during assembly of the bearing seal, the thrust bumper having a modified axial thickness less than the initial axial thickness after a break-in phase of the bearing seal;

the thrust bumper being composed of a material that is at least 90% polytetrafluoroethylene by weight and includes at least one additive selected from the group consisting of carbon fiber, graphite, glass fiber, and molybdenum disulfide.

2. The bearing seal of claim 1 , the material being uniform throughout the thrust bumper.

3. The bearing seal of claim 1 , the thrust bumper being characterized by at least fifty percent maximum elongation at twenty degrees Celsius.

4. The bearing seal of claim 1 , the thrust bumper being mounted to an axial leg of the seal case, the sleeve including an inner radial leg, an outer radial leg, and an axial leg connecting the inner radial leg to the outer radial leg, the outer radial leg terminating in an edge that faces the thrust bumper.

5. The bearing seal of claim 4 , each of the edge and the thrust bumper being rotationally symmetric about the rotation axis, a radial extent of the edge being bounded by an inner diameter and an outer diameter, the thrust bumper including a planar surface facing the edge, a radial extent of the planar surface including and exceeding the radial extent of the edge.

6. The bearing seal of claim 5 , the thrust bumper having a rectangular cross section in a plane that includes the rotation axis.

7. The bearing seal of claim 4 , further including a rubber gasket over-molded on the seal case, the thrust bumper being seated in the rubber gasket.

8. A method for breaking in a bearing seal, comprising:

rotating a seal case of the bearing seal relative to a sleeve of the bearing seal to create abrasion that reduces an axial thickness of a thrust bumper of the bearing seal;

wherein:

the thrust bumper is disposed between the seal case and the sleeve;

the axial thickness, prior to said rotating, defines a spacing between the seal case and the sleeve;

the thrust bumper is composed of a material that is at least 90% polytetrafluoroethylene by weight; and

the abrasion generates lubricative debris formed from the material that is at least 90% polytetrafluoroethylene by weight.

9. The method of claim 8 , wherein:

the thrust bumper is mounted to the seal case; and

said rotating creates abrasion between the sleeve and the thrust bumper.

10. The method of claim 9 , wherein the abrasion opens a gap between the sleeve and the thrust bumper.

11. The method of claim 9 , wherein:

the thrust bumper is mounted to an axial leg of the seal case;

the sleeve of the bearing seal includes an inner radial leg, an outer radial leg, and an axial leg connecting the inner radial leg to the outer radial leg, the outer radial leg terminating in a sleeve edge that faces the thrust bumper; and

said rotating creates abrasion between the sleeve edge and the thrust bumper.

12. The method of claim 11 , wherein:

the sleeve edge and thrust bumper are both rotationally symmetric about a rotation axis of the bearing seal;

the sleeve edge has a radial extent that extends between an inner diameter and an outer diameter;

the thrust bumper has a planar surface facing the sleeve edge, the planar surface having a radial extent that includes and exceeds the radial extent of the sleeve edge; and

said rotating creates abrasion between the sleeve edge and the planar surface of the thrust bumper.

13. The method of claim 8 , wherein:

the thrust bumper is mounted to the sleeve; and

said rotating creates abrasion between the seal case and the thrust bumper.

14. The method of claim 13 , wherein the abrasion opens a gap between the seal case and the thrust bumper.

15. The method of claim 8 , further comprising installing the bearing seal by:

affixing the seal case to a hub assembly of a wheel end; and

affixing the sleeve to an axle of the wheel end.

16. The method of claim 8 , further comprising assembling the bearing seal by compressing the seal case and sleeve together with the thrust bumper therebetween.

17. The method of claim 8 , wherein the lubricative debris comprises flakes having a flake size less than 0.003 inches.