Jeep Wrangler Unlimited (2012 year). Instruction

Enabling HDC

1. Shift the transfer case into 4WD LOW range. Refer to
“Four-Wheel Drive Operation” in “Starting and Operat-
ing” for further information.

2. Press the “Hill Descent” button. The “Hill Descent
Control Indicator Light” in the instrument cluster will
turn on solid.

NOTE:

If the transfer case is not in 4WD LOW range,

the “Hill Descent Control Indicator Light” will flash for
five seconds and HDC will not be enabled.

Disabling HDC

1. Press the “Hill Descent” button or shift the transfer
case out of 4WD LOW range. The “Hill Descent Control
Indicator” light in the instrument cluster will turn off.

TIRE SAFETY INFORMATION

Tire Markings

1 — U.S. DOT Safety

Standards Code (TIN)

4 — Maximum Load

2 — Size Designation

5 — Maximum Pressure

3 — Service Description

6 — Treadwear, Traction and

Temperature Grades

432

STARTING AND OPERATING

NOTE:

• P (Passenger) - Metric tire sizing is based on U.S.

design standards. P-Metric tires have the letter “P”
molded into the sidewall preceding the size designa-
tion. Example: P215/65R15 95H.

• European-Metric tire sizing is based on European

design standards. Tires designed to this standard have
the tire size molded into the sidewall beginning with
the section width. The letter

⬙P⬙ is absent from this tire

size designation. Example: 215/65R15 96H.

• LT (Light Truck) - Metric tire sizing is based on U.S.

design standards. The size designation for LT-Metric

tires is the same as for P-Metric tires except for the
letters “LT” that are molded into the sidewall preced-
ing the size designation. Example: LT235/85R16.

• Temporary spare tires are spares designed for tempo-

rary emergency use only. Temporary high pressure
compact spare tires have the letter “T” or “S” molded
into the sidewall preceding the size designation. Ex-
ample: T145/80D18 103M.

• High flotation tire sizing is based on U.S. design

standards, and it begins with the tire diameter molded
into the sidewall. Example: 31x10.5 R15 LT.

STARTING AND OPERATING

433

Tire Sizing Chart

EXAMPLE:

Size Designation:

= Passenger Car tire size based on U.S. design standards

ⴖ....blank....ⴖ = Passenger Car tire based on European design standards
LT

= Light Truck tire based on U.S. design standards

T or S

= Temporary compact spare tire

= Overall diameter in inches (in)

215

= Section width in millimeters (mm)

= Aspect ratio in percent (%)

— Ratio of section height to section width of tire

10.5

= Section width in inches (in)

= Construction code

—

⬙R⬙ means radial construction

—

⬙D⬙ means diagonal or bias construction

= Rim diameter in inches (in)

434

STARTING AND OPERATING

EXAMPLE:

Service Description:

= Load Index

— A numerical code associated with the maximum load a tire can carry

= Speed Symbol

— A symbol indicating the range of speeds at which a tire can carry a load corresponding
to its load index under certain operating conditions
— The maximum speed corresponding to the speed symbol should only be achieved under
specified operating conditions (i.e., tire pressure, vehicle loading, road conditions, and
posted speed limits)

Load Identification:

ⴖ....blank....ⴖ = Absence of any text on the sidewall of the tire indicates a Standard Load (SL) Tire
Extra Load (XL)

= Extra load (or reinforced) tire

Light Load (LL)

= Light load tire

C, D, E, F, G

= Load range associated with the maximum load a tire can carry at a specified pressure

Maximum Load

— Maximum load indicates the maximum load this tire is designed to carry

Maximum Pressure

— Maximum pressure indicates the maximum permissible cold tire inflation pressure for

this tire

STARTING AND OPERATING

435

Tire Identification Number (TIN)
The TIN may be found on one or both sides of the tire,
however, the date code may only be on one side. Tires
with white sidewalls will have the full TIN, including the
date code, located on the white sidewall side of the tire.

Look for the TIN on the outboard side of black sidewall
tires as mounted on the vehicle. If the TIN is not found on
the outboard side, then you will find it on the inboard
side of the tire.

EXAMPLE:

DOT MA L9 ABCD 0301

DOT

= Department of Transportation

— This symbol certifies that the tire is in compliance with the U.S. Department of Transportation tire
safety standards, and is approved for highway use

= Code representing the tire manufacturing location (two digits)

= Code representing the tire size (two digits)

ABCD

= Code used by the tire manufacturer (one to four digits)

= Number representing the week in which the tire was manufactured (two digits)

—03 means the 3rd week.

= Number representing the year in which the tire was manufactured (two digits)

—01 means the year 2001
— Prior to July 2000, tire manufacturers were only required to have one number to represent the
year in which the tire was manufactured. Example: 031 could represent the 3rd week of 1981 or 1991

436

STARTING AND OPERATING

Tire Terminology And Definitions

Term

Definition

B-Pillar

The vehicle B-Pillar is the structural member of the body located
behind the front door.

Cold Tire Inflation Pressure

Cold tire inflation pressure is defined as the tire pressure after the
vehicle has not been driven for at least 3 hours, or driven less
than 1 mile (1.6 km) after sitting for a three hour period. Inflation
pressure is measured in units of PSI (pounds per square inch) or
kPa (kilopascals).

Maximum Inflation Pressure

The maximum inflation pressure is the maximum permissible cold
tire inflation pressure for this tire. The maximum inflation pres-
sure is molded into the sidewall.

Recommended Cold Tire Inflation
Pressure

Vehicle manufacturer’s recommended cold tire inflation pressure
as shown on the tire placard.

Tire Placard

A paper label permanently attached to the vehicle describing the
vehicle’s loading capacity, the original equipment tire sizes and
the recommended cold tire inflation pressures.

STARTING AND OPERATING

437

Tire Loading And Tire Pressure

Tire Placard Location

Tire Placard Location (Two-Door Models)

Tire Placard Location (Four-Door Models)

438

STARTING AND OPERATING

Tire And Loading Information Placard

This placard tells you important information about
the:
1) number of people that can be carried in the vehicle
2) total weight your vehicle can carry
3) tire size designed for your vehicle
4) cold tire inflation pressures for the front, rear, and
spare tires.

Loading
The vehicle maximum load on the tire must not exceed
the load carrying capacity of the tire on your vehicle. You
will not exceed the tire’s load carrying capacity if you
adhere to the loading conditions, tire size, and cold tire
inflation pressures specified on the Tire and Loading
Information placard and in the “Vehicle Loading” section
of this manual.

Tire and Loading Information Placard

STARTING AND OPERATING

439

NOTE:

Under a maximum loaded vehicle condition,

gross axle weight ratings (GAWRs) for the front and rear
axles must not be exceeded. For further information on
GAWRs, vehicle loading, and trailer towing, refer to
“Vehicle Loading” in this section.

To determine the maximum loading conditions of your
vehicle, locate the statement “The combined weight of
occupants and cargo should never exceed XXX kg or XXX
lbs.” on the Tire and Loading Information placard. The
combined weight of occupants, cargo/luggage and
trailer tongue weight (if applicable) should never exceed
the weight referenced here.

Steps For Determining Correct Load Limit

1. Locate the statement “The combined weight of occu-
pants and cargo should never exceed XXX kg or XXX lbs”
on your vehicle’s placard.

2. Determine the combined weight of the driver and
passengers that will be riding in your vehicle.

3. Subtract the combined weight of the driver and pas-
sengers from XXX kg or XXX lbs.

4. The resulting figure equals the available amount of
cargo and luggage load capacity. For example, if “XXX”
amount equals 1,400 lbs (635 kg) and there will be five
150 lb (68 kg) passengers in your vehicle, the amount of
available cargo and luggage load capacity is 650 lbs
(295 kg) (since 5 x 150 = 750, and 1400 – 750 = 650 lbs
[295 kg]).

440

STARTING AND OPERATING

5. Determine the combined weight of luggage and cargo
being loaded on the vehicle. That weight may not safely
exceed the available cargo and luggage load capacity
calculated in Step 4.

6. If your vehicle will be towing a trailer, load from your
trailer will be transferred to your vehicle. Consult this
manual to determine how this reduces the available
cargo and luggage load capacity of your vehicle.

NOTE:

• The following table shows examples on how to calcu-

late total load, cargo/luggage, and towing capacities
of your vehicle with varying seating configurations
and number and size of occupants. This table is for
illustration purposes only and may not be accurate for
the seating and load carry capacity of your vehicle.

• For the following example, the combined weight of

occupants and cargo should never exceed 865 lbs
(392 kg).

STARTING AND OPERATING

441

WARNING!

Overloading of your tires is dangerous. Overloading
can cause tire failure, affect vehicle handling, and
increase your stopping distance. Use tires of the
recommended load capacity for your vehicle. Never
overload them.

TIRES — GENERAL INFORMATION

Tire Pressure
Proper tire inflation pressure is essential to the safe and
satisfactory operation of your vehicle. Three primary
areas are affected by improper tire pressure:

Safety

WARNING!

• Under-inflation increases tire flexing and can re-

sult in over-heating and tire failure.

• Over-inflation reduces a tire’s ability to cushion

shock. Objects on the road and chuck holes can
cause damage that results in tire failure.

• Over-inflated or under-inflated tires can affect

vehicle handling and can fail suddenly, resulting
in loss of vehicle control.

• Unequal tire pressures can cause steering prob-

lems. You could lose control of your vehicle.

• Unequal tire pressures from one side of the ve-

hicle to the other can cause the vehicle to drift to
the right or left.

STARTING AND OPERATING

443

Economy
Improper inflation pressures can cause uneven wear
patterns to develop across the tire tread. These abnormal
wear patterns will reduce tread life resulting in a need for
earlier tire replacement. Under-inflation also increases
tire

rolling

resistance

resulting

higher

fuel

consumption.

Ride Comfort And Vehicle Stability
Proper tire inflation contributes to a comfortable ride.
Over-inflation produces a jarring and uncomfortable
ride.

Tire Inflation Pressures
Tire pressure should be checked and adjusted as well as
inspected for signs of tire wear or visible damage, at least
once a month. Use a good quality pocket-type gauge to
check tire pressure. Do not make a visual judgement
when determining proper inflation. Radial tires may look
properly inflated even when they are under-inflated.

CAUTION!

After inspecting or adjusting the tire pressure, al-
ways reinstall the valve stem cap. This will prevent
moisture and dirt from entering the valve stem,
which could damage the Tire Pressure Monitoring
Sensor.

Inflation pressures specified on the placard are always
“cold tire inflation pressure.” Cold tire inflation pressure
is defined as the tire pressure after the vehicle has not
been driven for at least three hours, or driven less than
1 mile (1.6 km) after a three-hour period. The cold tire
inflation pressure must not exceed the maximum infla-
tion pressure molded into the tire side wall.

Check tire pressures more often if subject to a wide range
of outdoor temperatures, as tire pressures vary with
temperature changes.

444

STARTING AND OPERATING

Tire pressures change by approximately 1 psi (7 kPa) per
12° F (7° C) of air temperature change. Keep this in mind
when checking tire pressure inside a garage, especially in
the Winter.

Example: If garage temperature = 68° F (20° C) and the
outside temperature = 32° F (0° C) then the cold tire
inflation pressure should be increased by 3 psi (21 kPa),
which equals 1 psi (7 kPa) for every 12° F (7° C) for this
outside temperature condition.

Tire pressure may increase from 2 to 6 psi (13 to 40 kPa)
during operation. DO NOT reduce this normal pressure
buildup or your tire pressure will be too low.

Tire Pressures For High-Speed Operation
The manufacturer advocates driving at safe speeds
within posted speed limits. Where speed limits or condi-
tions are such that the vehicle can be driven at high
speeds, maintaining correct tire inflation pressure is very
important. Increased tire pressure and reduced vehicle
loading may be required for high-speed vehicle opera-
tion. Refer to original equipment or an authorized tire
dealer for recommended safe operating speeds, loading
and cold tire inflation pressures.

WARNING!

High speed driving with your vehicle under load is
dangerous. The added strain on your tires could
cause them to fail. You could have a serious collision.
Do not drive a vehicle loaded to maximum capacity at
continuous speeds above 75 mph (120 km/h).

STARTING AND OPERATING

445

Radial-Ply Tires

WARNING!

Combining radial ply tires with other types of tires
on your vehicle will cause your vehicle to handle
poorly. The instability could cause a collision. Al-
ways use radial tires in sets of four. Never combine
them with other types of tires.

Cuts and punctures in radial tires are repairable only in
the tread area because of sidewall flexing. Consult your
authorized dealer for radial tire repairs.

Spare Tire Matching Original Equipped Tire And
Wheel – If Equipped
Your vehicle may be equivalent with a spare tire and
wheel in look and function as the original equipment tire
and wheel found on the front or rear axle of your vehicle.
This spare tire may be used in the tire rotation for your

vehicle. If your vehicle has this option refer to an
authorized tire dealer for the recommended tire rotation
pattern.

If your vehicle is not equipped with an original equip-
ment tire and wheel as a spare, a non-matching tempo-
rary emergency use spare may be equipped with your
vehicle. Temporary use spares are engineered to be used
only with your vehicle. Your vehicle may be equipped
with one of the following types of non-matching tempo-
rary use spares; compact, full size, or limited-use. Do not
install more than one non-matching temporary use spare
tire/wheel on the vehicle at any given time.

CAUTION!

Because of the reduced ground clearance, do not take
your vehicle through an automatic car wash with a
compact, full size or limited-use temporary spare
installed. Damage to the vehicle may result.

446

STARTING AND OPERATING

Compact Spare Tire – If Equipped
The compact spare is for temporary emergency use only.
You can identify if your vehicle is equipped with a
compact spare by looking at the spare tire description on
the Tire and Loading Information Placard located on the
driver’s side door opening or on the sidewall of the tire.
Compact spare tire descriptions begin with the letter “T”
or “S” preceding the size designation. Example: T145/
80D18 103M.

T, S = Temporary Spare Tire

Since this tire has limited tread life the original equip-
ment tire should be repaired (or replaced) and reinstalled
on your vehicle at the first opportunity.

Do not install a wheel cover or attempt to mount a
conventional tire on the compact spare wheel, since the
wheel is designed specifically for the compact spare tire.
Do not install more than one compact spare tire and
wheel on the vehicle at any given time

WARNING!

Compact spares are for temporary emergency use
only. With these spares, do not drive more than
50 mph (80 km/h). Temporary use spares have limited
tread life. When the tread is worn to the tread wear
indicators, the temporary use spare tire needs to be
replaced. Be sure to follow the warnings, which
apply to your spare. Failure to do so could result in
spare tire failure and loss of vehicle control.

Full Size Spare – If Equipped
The full size spare is for temporary emergency use only.
This tire may look like the original equipped tire on the
front or rear axle of your vehicle, but it is not. This spare
tire may have limited tread life. When the tread is worn
to the tread wear indicators, the temporary use full size
spare tire needs to be replaced. Since it is not the same as

STARTING AND OPERATING

447

Jeep Wrangler Unlimited (2012 year). Instruction - part 28