516 OperationTires and wheels
Reactivating the Run Flat Indicator
The tire inflation pressure monitor must be
reactivated in the following situations:
If you have changed the tire inflation
pressure
If you have replaced the wheels or tires
If you have installed new wheels or
tires
Using the tire placard on the driver’s
door B-pillar (
page 503) or, if avail-
able, the inside of the fuel filler flap
(
page 489), make sure the tire infla-
tion pressure of all four tires is correct.
Switch on the ignition (
page 315).
Press( or& to select the menu
“Service”.
Press$ or% to select “Tire
pressure”.
Press#.
The message
Run Flat Indicator
active
Reactivation possible: OK
appears in the multifunction display.
Press#.
The message
Tire pressure
now OK?
appears in the multifunction display.
Warning!
G
The Run Flat Indicator does not provide a
warning for wrongly selected tire inflation
pressures. Always adjust tire inflation pres-
sure according to the placard on the driver’s
door B-pillar or fuel filler flap.
The Run Flat Indicator does not replace reg-
ular checks of the tire inflation pressures
since a gradual pressure loss in all four tires
cannot be detected by the Run Flat
Indicator.
The Run Flat Indicator is not able to issue a
warning due to a sudden dramatic loss of
tire inflation pressure (e.g. tire blowout
caused by a foreign object). In this case
bring the vehicle to a halt by carefully apply-
ing the brakes and avoiding abrupt steering
maneuvers.
Warning!
G
The Run Flat Indicator can only warn you in
a reliable manner if you have set the correct
tire inflation pressures for each tire.
If an incorrect tire inflation pressure was
set, the system will monitor the pressure ac-
cording to the incorrect value.
i
The menu overview can be found on
(
page 243).
517 Operation
Tires and wheels
If you wish to confirm activation:
Press$ or% to select “Yes”.
Press#.
The message
Run Flat Indicator
reactivated
appears in the multifunction display.
After a certain “learning phase”, the Run
Flat Indicator checks the set pressure val-
ues for all four tires.
If you wish to cancel activation:
PressL.
or
When the message
Tire pressure
now OK?
appears in the multifunction display:
Press$ or% to select “No”.
Press#.Potential problems associated with
underinflated and overinflated tires
Underinflated tires
Underinflated tires can:
cause excessive and uneven tire wear
adversely affect fuel economy
lead to tire failure from being
overheated
adversely affect handling
characteristicsOverinflated tires
Overinflated tires can:
adversely affect handling
characteristics
cause uneven tire wear
be more prone to damage from road
hazards
adversely affect ride comfort
increase stopping distance
Warning!
G
Follow recommended tire inflation
pressures.
Do not underinflate tires. Underinflated tires
wear excessively and / or unevenly,
adversely affect handling and fuel economy,
and are more likely to fail from being
overheated.
Warning!
G
Follow recommended tire inflation
pressures.
Do not overinflate tires. Overinflated tires
can adversely affect handling and ride
comfort, wear unevenly, increase stopping
distance, and result in sudden deflation
(blowout) because they are more likely to
become punctured or damaged by road
debris, potholes etc.
518 OperationTires and wheelsTire labeling
Besides tire name (sales designation) and
manufacturer name, a number of markings
can be found on a tire.
Following are some explanations for the
markings on your vehicle’s tires:1Uniform Quality Grading Standards
(
page 524)
2DOT, Tire Identification Number (TIN)
(page 522)
3Maximum tire load (
page 523)
4Maximum tire inflation pressure
(
page 523)
5Manufacturer
6Tire ply material (
page 525)
7Tire size designation, load and speed
rating (
page 518)
8Load identification (
page 521)
9Tire nameTire size designation, load and speed
rating
1Tire width
2Aspect ratio in %
3Radial tire code
4Rim diameter
5Tire load rating
6Tire speed rating
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
For more information, see “Rims and tires”
(
page 655).
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
519 Operation
Tires and wheels
General:
Depending on the design standards used,
the tire size molded into the sidewall may
have no letter or a letter preceding the tire
size designation.
No letter preceding the size designation
(as illustrated above): Passenger car tire
based on European design standards.
Letter “P” preceding the size designation:
Passenger car tire based on U.S. design
standards.
Letter “LT” preceding the size designation:
Light Truck tire based on U.S. design
standards.
Letter “T” preceding the size designation:
Temporary spare tires which are high
pressure compact spares designed for
temporary emergency use only. Tire width
The tire width1 (
page 518) indicates
the nominal tire width in mm.
Aspect ratio
The aspect ratio2 (page 518) is the
dimensional relationship between tire
section height and section width and is
expressed in percentage. The aspect ratio
is arrived at by dividing section height by
section width.
Tire code
The tire code3 (
page 518) indicates
the tire construction type. The “R” stands
for radial tire type. Letter “D” means diag-
onal or bias ply construction; letter “B”
means belted-bias ply construction.
At the tire manufacturer’s option, any tire
with a speed capability above 149 mph
(240 km/h) can include a “ZR” in the size
designation (for example: 245/40 ZR 18).
For additional information, see “Tire speed
rating” (
page 520).Rim diameter
The rim diameter4 (
page 518) is the
diameter of the bead seat, not the
diameter of the rim edge. Rim diameter is
indicated in inches (in).
Tire load rating
The tire load rating5 (page 518) is a
numerical code associated with the
maximum load a tire can support.
For example, a load rating of 91 corre-
sponds to a maximum load of 1 356 lbs
(615 kg) the tire is designed to support.
See also “Maximum tire load”
(
page 523) where the maximum load as-
sociated with the load index is indicated in
kilograms and lbs.
520 OperationTires and wheels
For additional information on tire load
rating, see “Load identification”
(page 521).
Tire speed rating
The tire speed rating6 (
page 518)
indicates the approved maximum speed
for the tire.Summer tires
At the tire manufacturer’s option, any
tire with a speed capability above
149 mph (240 km/h) can include a
“ZR” in the size designation (for exam-
ple: 245/40 ZR18). To determine the
maximum speed capability of the tire,
Warning!
G
The tire load rating must always be at least
half of the GAWR (
page 526) of your vehi-
cle. Otherwise, tire failure may be the result
which may cause an accident and/or seri-
ous personal injury to you or others.
Always replace rims and tires with the same
designation, manufacturer and type as
shown on the original part.
Warning!
G
Do not overload the tires by exceeding the
specified load limit or vehicle capacity
weight as indicated on the placard located
on the driver’s door B-pillar (
page 503).
Overloading the tires can overheat them,
possibly causing a blowout. Overloading the
tires can also result in handling or steering
problems, or brake failure.
i
Tire load rating5 (
page 518) and tire
speed rating6 (
page 518) are also referred
to as “service description”.
Warning!
G
Even when permitted by law, never operate
a vehicle at speeds greater than the
maximum speed rating of the tires.
Exceeding the maximum speed for which
tires are rated can lead to sudden tire
failure, causing loss of vehicle control and
possibly resulting in an accident and/or
personal injury and possible death, for you
and for others.
i
Tire load rating5 (
page 518) and tire
speed rating6 (
page 518) are also referred
to as “service description”.
Index
Speed rating
Q
up to 100 mph (160 km/h)
R
up to 106 mph (170 km/h)
S
up to 112 mph (180 km/h)
T
up to 118 mph (190 km/h)
H
up to 130 mph (210 km/h)
V
up to 149 mph (240 km/h)
W
up to 168 mph (270 km/h)
Y
up to 186 mph (300 km/h)
(Y)
above 186 mph (300 km/h)
ZR
above 149 mph (240 km/h)
521 Operation
Tires and wheels
the service description for the tire must
be referred to. The service description
is comprised of the tire load rating5
(page 518) and the tire speed
rating6 (
page 518).
If your tire includes “ZR” in the size
designation and no service
description5 and6 (
page 518) is
given, the tire manufacturer must be
consulted for the maximum speed ca-
pability.
If a service description5 and6
(
page 518) is given, the speed capa-
bility is limited by the speed symbol in
the service description.
Example: 245/40 ZR18 97Y.
In this example, “97Y” is the service
description. The letter “Y” designates
the speed rating and the speed capabil-
ity of the tire is limited to 186 mph
(300 km/h).
Any tire with a speed capability above
186 mph (300 km/h) must include a
“ZR” in the size designation AND the
service description must be placed in
parenthesis.
Example: 275/40 ZR 18 (99Y).
The “(Y)” speed rating in parenthesis
designates the maximum speed capa-
bility of the tire as being above
186 mph (300 km/h). Consult the tire
manufacturer for the actual maximum
permissible speed of the tire.
All-season and winter tires
Load identification
1Load identification
Index
Speed rating
QM+S
1
1or M+S.for winter tires
up to 100 mph (160 km/h)
TM+S
1
up to 118 mph (190 km/h)
HM+S
1
up to 130 mph (210 km/h)
VM+S
1
up to 149 mph (240 km/h)
i
Not all M+S rated tires provide special win-
ter performance. Make sure the tires you use
show M+S and the mountain/snow-
flake.
marking on the tire sidewall. These
tires meet specific snow traction performance
requirements of the Rubber Manufacturers As-
sociation (RMA) and the Rubber Association of
Canada (RAC) and have been designed specifi-
cally for use in snow conditions.
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
522 OperationTires and wheelsIn addition to tire load rating, special load
information may be molded into the tire
sidewall following the letter designating
the tire speed rating6 (
page 518).
No specification given: absence of any text
(like in above example) indicates a
standard load (SL) tire.
XL (Extra Load): designates an extra load
(or reinforced) tire.
Light Load: designates a light load tire.
C, D, E: designates load range associated
with the maximum load a tire can carry at
a specified pressure.
DOT, Tire Identification Number (TIN)
U.S. tire regulations require each new tire
manufacturer or tire retreader to mold a
TIN into or onto a sidewall of each tire
produced.
The TIN is a unique identifier which facili-
tates efforts by tire manufactures to notify
purchasers in recall situations or other safety matters concerning tires and gives
purchasers the means to easily identify
such tires.
The TIN is comprised of “Manufacturer’s
identification mark”, “Tire size”, “Tire type
code” and “Date of manufacture”.
1DOT
2Manufacturer’s identification mark
3Tire size
4Tire type code (at the option of the tire
manufacturer)
5Date of manufactureDOT (D
epartment o
f T
ransportation)
A tire branding symbol1 (
page 522)
which denotes the tire meets require-
ments of the U.S. Department of Transpor-
tation.
Manufacturer’s identification mark
The manufacturer’s identification mark2
(
page 522) denotes the tire
manufacturer.
New tires have a mark with two symbols.
Retreaded tires have a mark with four sym-
bols. For more information on retreaded
tires (
page 500).
Tire size
The code3 (
page 522) indicates the
tire size.
Tire type code
The code4 (page 522) may, at the
option of the manufacturer, be used as a
descriptive code for identifying significant
characteristics of the tire.
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
523 Operation
Tires and wheels
Date of manufacture
The date of manufacture5 (
page 522)
identifies the week and year of manufac-
ture.
The first two figures identify the week,
starting with “01” to represent the first full
week of the calendar year. The second two
figures represent the year.
For example, “3202” represents the 32nd
week of 2002.
Maximum tire load
1Maximum tire load ratingThe maximum tire load is the maximum
weight the tires are designed to support.
For more information on tire load rating
(
page 519).
For information on calculating total and
cargo load capacities (
page 505).
Maximum tire inflation pressure
1Maximum permissible tire inflation
pressure
This is the maximum permissible tire
inflation pressure for the tire.
Always follow the recommended tire
inflation pressure (
page 509) for proper
tire inflation.
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.Warning!
G
Do not overload the tires by exceeding the
specified load limit or vehicle capacity
weight as indicated on the placard located
on the driver’s door B-pillar (
page 503).
Overloading the tires can overheat them,
possibly causing a blowout. Overloading the
tires can also result in handling or steering
problems, or brake failure.
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.