wheel size FORD F750 2012 12.G Owners Manual

At regular intervals, or during other scheduled maintenance (tire
rotation/service, wheel bearing service, alignment, etc.), the kingpins
should be checked for excessive wear. Refer to the service manual for
proper procedures.
Toe-in setting - general inspection
Inspecting steer axle tires in the first 3,000–10,000 service miles
(5,000–16,000 service km) generally shows if tires are wearing normally.
Rapid outside shoulder wear on both tires indicates too much toe-in.
Rapid inside shoulder wear on both tires indicates too much toe-out. In
P&D-type service, left-to-right steer tire tread life differentials up to 40%
can be observed depending on routes and other variables.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, load range (ply rating) and steer axle loading typical for
their operation (each steer axle tire equals
12steer axle loading).
Special applications may warrant a setting based on experience with the
type of tire operating loads and conditions. Radial tires are more
sensitive to toe-in setting than bias ply tires. While not insensitive to
vehicle alignment, fine tuning school bus alignment to line-haul truck
standards does not drastically improve tire tread life.
It is essential that correct toe-in and tire pressure be maintained for
optimum tire wear.
Rear axle - general inspection
Make sure that the axle mounting U-bolts, attaching or mounting bolts
and nuts are securely tightened. Refer toU-bolt nut torquein this
chapter. Regularly check the rear axle for damaged, binding or worn
parts.
NoSpin Detroit Locker positive locking differential
Vehicles equipped with this type differential have the operator’s manual
supplied with the vehicle. Refer to this manual for maintenance checks.
Maintenance and Specifications
183
2012 F-650/750(f67)
Supplement, 2nd Printing
USA(fus)

Changing wheel types
Consult your dealer or wheel/rim distributor before attempting any wheel
or fastener changes.
WARNING:Use only the same type and style wheels and
mounting hardware to replace original parts. Failure to do so
may result in an assembly that looks fine, but does not fit together
properly. This could possibly cause wheel or fastener failures which
could result in property damage, personal injury or death.
Note:Do not attempt to mix stud-piloted wheels or fasteners with
hub-piloted wheels or fasteners.
Note:Do not change from aluminum wheels to steel wheels or
vice-versa without changing the mounting hardware required or, with
flange-nut mounting systems, changing the hub and stud assembly.
WHEEL NUT TORQUE
Size Nut mountingTorque
ft-lb N•m
22 mm Flange 450–500 610–678
Note:Do not use lubrication on dry threads. Where excessive corrosion
exists, a light coat of lubricant on the first three threads of the stud bolt
is permitted. Keep lubricant away from:
•Hex nut and rim clamp contact surfaces.
•Cap nut ball face and ball seat on the disc wheel.
•Flange nut washer surface and flat on the disc wheel.
Maintenance and Specifications
237
2012 F-650/750(f67)
Supplement, 2nd Printing
USA(fus)

Stay out of the trajectory (1) as indicated in the illustration.
WARNING:Do not mount tube type tires on tubeless wheels or
tubeless tires on tube type wheels. To do so could result in tire
or wheel failure and cause property damage, personal injury or death.
Preserving proper inflation pressure is a very important maintenance
practice to insure safe vehicle operation and long life for the tires.
Failure to maintain correct inflation pressure may result in sudden tire
destruction, improper vehicle handling, and may cause rapid and
irregular tire wear. Therefore, inflation pressures should be checked daily
and always before long distance trips.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, type, load range (ply rating) and axle loading typical for
your operation. (Each steer axle tire load equals
12steer axle loading;
each drive tire load is14the axle loading if fitted with four tires).
Checking inflation
Always check inflation pressure when tires are cold. Never bleed air from
hot tires to relieve normal pressure build-up. Normal increases in
pressure due to service conditions is 10–15 psi (69–103 kPa), which is
allowable in truck tires.
Maintenance and Specifications
240
2012 F-650/750(f67)
Supplement, 2nd Printing
USA(fus)

Loads
WARNING:Loading tires beyond their rated capacity decreases
tire life requiring more frequent replacement of tires.
Overloading creates an unsafe condition that may result in sudden air
loss from a tire failure resulting in an accident that could cause
property damage, personal injury or death.
Note:Your GAW/GVW rating is correct at the time of your vehicle
production, and reflects the exact rating of the tires specified. When
replacing tires be sure that the replacement tire load rating (listed in
pounds and kilograms on the tire sidewall) is the same or higher than
the tire that is removed. Failure to do so adversely affects maximum load
carrying capacity. Tires with the same size specification do not always
have the same load specification.
Matching
Dual Tires:Dual tires should be matched using tires of equivalent size.
Tires which differ more than
14inch (6 mm) in diameter or34inch
(19 mm) in circumference should not be mounted on the same dual
wheel assembly.
Mixing:Never mix bias and radial tires on this vehicle. Never mix
different tire sizes or constructions on the same axle.
Rotation:
Rotation is always advisable:
1. If front (steering) axle tires become irregularly worn, move to rear
position.
2. In a dual assembly, reverse the position of the tires if one tire wears
much faster than its mate.
3. On the drive axle, if heel and toe wear or alternate lug wear occurs,
rotating the tires from one end of the axle to the other end of the axle
may help even out this wear.
Rotation may not advisable:
1.Front (Steering) Axle:Tires must be removed when tread is worn
to 4/32 inch (3 mm) or less. Retread or rotate worn tires to drive
position. Retreaded tires are not recommended to be used on steering
axles.
2.Rear Axles:Tires must be removed when tread is worn to 2/32 inch
(2 mm).
Maintenance and Specifications
242
2012 F-650/750(f67)
Supplement, 2nd Printing
USA(fus)