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Copyright 2001 Society of Automotive Engineers, Inc.All rights reserved.
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SAE J2535 Issued MAR2001
1.1
Purpose—The purpose of this document is to list acceptable axial bearing preload force values forconventional wheel-end components used in heavy-duty tractors and trailers.
The audience of this documet is intended to be the axle and/or component engineers. The user should beaware of both the benefits and the risks of this practice.
a.Benefits—Bearing and seal life can be maximized when the bearings are adjusted to a light, controlled
preload setting.
b.Risks—The benefits of a light and controlled preload bearing setting are negated if bearing preload
force is excessive. Care must be taken to ensure that preload force does not exceed therecommended amounts. Excessive preload can cause high operating temperatures, reduced lubricantlife, reduced seal life, and premature bearing damage. Bearing lock-up and/or wheel-end assemblyseparation may occur if the preload force is excessive. A light preload bearing setting should only beattempted if the entire bearing setting process is accurate and repeatable.For adjustment recommendations where bearing end-play is desired, refer to The Maintenance Council (TMC)Recommended Practice #RP-618.2.2.1
References
Applicable Publications—The following publications form a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest version of SAE publications shall apply.
SAE PUBLICATION—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1842 SEP94—Axle End Standardization
2.1.2
TMC PUBLICATION—Available from The Maintenance Council, American Trucking Associations, 2200 MillRoad, Alexandria, VA 22314-5388.
TMC RP-618—Adjustment of Wheel Bearings
3.3.1
Definitions
End-play—An axial clearance between the bearing’s rolling elements and the races producing a measurableaxial wheel-end movement when a force is applied, first in one axial direction and then in the oppositedirection, after oscillating the wheel-end.
Preload—A load resulting from an axial interference between the bearing’s rolling elements and racesresulting in no discernible axial wheel-end movement when a force is applied, first in one axial direction andthen in the opposite direction, after oscillating the wheel-end.
Conventional Wheel-end—A wheel-end assembly that consists of a hub, an inboard seal, two single rowtapered roller bearings, and fastening hardware (Figure 1). Conventional wheel-ends use the fastener toestablish bearing setting; they do not have a bearing spacer between the bearings.
Load Line—The distance from the inboard bearing cup backface to the center of the tire(s) contact (Figures 2and 3) which directly influences the relative wheel bearing load distribution.
2.1.1
3.2
3.3
3.4
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SAE J2535 Issued MAR2001
FIGURE 1—CONVENTIONAL WHEEL END
4.
Preload Settings—Target (which is the optimum preload force value) and maximum preload force values canbe found in columns “D” and “E” in Table 1. Suppliers and/or axle assemblers developing a preloadmethodology should take care to ensure that their fastener adjustment methodology never results in a finalsetting that exceeds the maximum value listed in column “E”.
TABLE 1—PRELOAD SETTINGS
“A”MaximumGAWR(Gross AxleWeight Rating)
N(lbs)
111 220(25 000)133 470(30 000)65 390(14 700) 113 450(25 500)
“D”TargetPreloadForceN(lbf)2 220(500)2 220(500)1 110(250)2 220(500)
“E”MaximumPreloadForceN(lbf)4 450(1 000)4 450(1 000)2 220(500)4 450(1 000)
SAE Configuration“N”
trailer axle“R”
powered rear axle“FF / FG”
nonpowered front axle“P”
trailer axle
“B”MinimumLoad Line(1)
mm(in)
23.1(0.91)46.2(1.82)–24.9(–0.98)48.8(1.92)
“C”MaximumLoad Line(1)
mm(in)
52.3(2.06)75.2(2.96)42.9(1.69)78.0(3.07)
1.Load line position is measured from the inboard bearing cup backface, the sign convention is explained in Figures 2 and 3.
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SAE J2535 Issued MAR2001
FIGURE 2—NONPOWERED FRONT
FIGURE 3—TRAILER OR POWERED REAR
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SAE J2535 Issued MAR2001
5.
Method Used to Determine Optimum Preload (for reference only)—To determine an optimum preloadrange for heavy-duty wheel bearings, it is necessary to calculate the life of the bearings across a specifiedrange of preload values. The bearing life calculations require a set of constants, a duty cycle, and wheel-enddesign data. Table 2 shows the assumptions that were held constant for each of the wheel-end preloadcalculations.
TABLE 2—CONSTANTS
Application Definition
Vehicle Center of Gravity(1)Track WidthTire RadiusBearing SpreadLubrication Type
(2)
Value used for Condition
1 969 mm (77.5 in)1 816 mm (71.5 in)508 mm (20.0 in)See SAE J1842OilInfinite
Wheel Hub Stiffness(2)
1.Vehicle Center of Gravity refers to the theoretical point of mass for the vehicle where forces act. It is measured vertically from the ground and is needed for vehicle dynamics calculations that affect bearing life.
2.Lubrication type and wheel hub stiffness have minimal effect on the cal-culated preload values.
Two duty cycles were used to determine the target and maximum preload for each of the axle configurations.The line-haul duty cycle simulates a vehicle operating under conditions where little turning is involved. Thecity-delivery duty cycle simulates a vehicle operating under more frequent turning conditions. Tables 3 and 4show the corresponding duty cycles.
TABLE 3—LINE HAUL DUTY CYCLE
VerticalAcceleration
(g)
1.01.01.0
HorizontalAcceleration
(g)
0.000.15–0.15
PercentDistance95%2.5%2.5%
ConditionStraight RoadRight TurnLeft Turn
TABLE 4—CITY DELIVERY DUTY CYCLE(1)
VerticalAcceleration
(g)
1.01.01.01.01.0
HorizontalAcceleration
(g)
0.000.25–0.250.15–0.15
PercentDistance70%13%13%2%2%
ConditionStraight RoadRight TurnLeft TurnRight TurnLeft Turn
1.This duty cycle was selected to evaluate frequent turning conditions. It is not intended to be used as a newly established or standardized duty cycle.
The axle weights were determined using ratings given by various axle manufacturers. Load line limits werecalculated from a collection of data for current hubs, disc wheels, and outboard mounted brake drums.Minimum and maximum dimensions from component features contributing to the load line were summed.Table 5 shows minimum and maximum axle weights and load line values used for each wheel-end calculation.
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SAE J2535 Issued MAR2001
Each wheel-end was analyzed using each combination of axle weight, load line, and duty cycle. Preloadtargets and maximum values were established based on bearing system life versus preload force for eachSAE configuration.
Several bearing manufacturers used their own calculation programs to calculate the optimum preload forces.The values published in this document were agreed upon by the contributing bearing manufacturers. Theinputs used to analyze the preload forces were accumulated for the purpose of this work alone; the data shouldnot be extrapolated to other calculations without consulting your bearing manufacturer.
TABLE 5—MINIMUM AND MAXIMUM AXLE WEIGHTS AND LOAD LINES
Bearing CupSpacingmm(in)
85.1(3.35)109.5(4.31)85.9(3.38)114.3(4.50)
MinimumAxleWeights
N(lbf)75 630(17 000)75 630(17 000)44 490(10 000)75 630(17 000)
MaximumAxleWeights
N(lbf)111 220(25 000)133 470(30 000)71 180(2)(16 000)133 470(2)(30 000)
MinimumLoad LinePositions(1)
mm(in)23.1(0.91)46.2(1.82)-24.9(-0.98)48.8(1.92)
MaximumLoad LinePositions(1)
mm(in)52.3(2.06)75.2(2.96)42.9(1.69)78.0(3.07)
SAE Configuration
“N”
trailer axle“R”
powered rear axle“FF / FG”
nonpowered front axle“P”
trailer axle
1.Load line position measured from the inboard bearing cup backface.
2.These values exceed the axle GAWR shown in Table 1. They were used for calculation purposes only.
PREPARED BY THE SAE TRUCK AND BUS WHEEL SUBCOMMITTEE OF THE
OF THE SAE TRUCK AND BUS CHASSIS COMMITTEE
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SAE J2535 Issued MAR2001
Rationale—Not applicable.
Relationship of SAE Standard to ISO Standard—Not applicable.
Application—This SAE Recommended Practice applies to the four primary, large volume applications in the
class 7-8 heavy-duty market place, as specified in SAE J1842:
a.b.c.d.
“N” trailer axle
“R” powered rear axle
“FF / FG” nonpowered front axle “P” trailer axle
This document applies to on-highway, disc wheel / outboard drum brake applications. It is not applicableto those applications that exceed the GAWR ratings or the load line restrictions listed in columns “A,” “B,”and “C” of Table 1. Load lines are measured from the inboard bearing cup backface as shown in 3.4.This document establishes preload force values only. The methodology to obtain these force valuesmust be determined by the fastener supplier and/or axle assembler.
This document reviews the bearing system. It is NOT intended to prescribe (new or existing) axle and/orhub manufacturers’ ratings and/or specifications.Reference Section
SAE J1842 SEP94—Axle End StandardizationTMC RP-618—Adjustment of Wheel Bearings
Developed by the SAE Truck and Bus Wheel SubcommitteeSponsored by the SAE Truck and Bus Chassis Committee
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