tire 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.
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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.
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Tires should be properly inflated to manufacturers recommended
pressure for the size and service load in which the vehicle is being used.
Refer to the specific tire manufacturer with which your vehicle is
equipped with for the latest information concerning service load and
inflation pressure.
It is particularly important to keep moisture from the inside of tires, and
proper selection of air compressor equipment, proper air line routing,
and the use of shop air dryers is strongly recommended to avoid
moisture in the high pressure air used for tire inflation.
Under-inflation
Tires should not be permitted to become under-inflated. Increased
flexing due to under-inflation causes heat build-up within the tire
components. This leads to reduced strength, breakdown of the rubber
compounds, and possible separation of the tire components (i.e., ply and
tread separation and reduced retreadability).
Under-inflation is the primary cause of premature tire concerns including
sudden loss of air. In addition, low inflation causes an increase in rolling
resistance. This results in reduced fuel mileage, a loss in tread mileage,
and uneven wear due to increased tread movement. To determine proper
inflation refer to the tire manufacturer load/inflation guide which can be
found on the tire manufacturer website or at your local truck tire dealer.
Inspection
Check condition of tires for abnormal wear patterns, and proper inflation
pressures. Cut or broken tire casing must be repaired or replaced.
Tires should be inspected for the following conditions. If any are present,
the tire should be removed and repaired, retreaded or scrapped as the
condition indicates.
•Any blister, bump or raised portion anywhere on the surface of the
tire tread or sidewall (other than a bump made by a repair). These
indicate the start of internal separation.
•Any cut that reaches to the belt or ply cords, or any cut that is large
enough to grow in size and depth.
•Any nail or puncturing object.
•If any stone or object is held by a tread groove and is starting to drill
into the tread base, remove the object.
Proper tire inflation, toe-in adjustment, loads, and road speeds are
important factors governing tire mileage, steering ease and maneuverability.
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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).
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