tire size MERCEDES-BENZ SL550 2008 R230 User Guide

316 Operation
Tires and wheels

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,
the service description for the tire must
be referred to. The service description
is comprised of the tire load rating5
(
page 313) and the tire speed
rating6 (
page 313).
If your tire includes “ZR” in the size
designation and no service
description5 and6 (
page 313) is
given, the tire manufacturer must be
consulted for the maximum speed ca-
pability. If a service description5 and6
(
page 313) 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 paren-
thesis designates the maximum speed
capability 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
IndexSpeed rating
QM+S1
1or M+S.for winter tires
up to 100 mph (160 km/h)
TM+S1up to 118 mph (190 km/h)
HM+S1up to 130 mph (210 km/h)
VM+S1up to 149 mph (240 km/h)
iNot all M+S rated tires provide special win-
ter performance. Make sure the tires you use
show M+S and the mountain/snowflake sym-
bol.marking on the tire sidewall. These tires
meet specific snow traction performance re-
quirements of the Rubber Manufacturers Associ-
ation (RMA) and the Rubber Association of
Canada (RAC) and have been designed specifi-
cally for use in snow conditions.

317 Operation
Tires and wheels
Load identification
1Load identificationIn addition to tire load rating, special load
identification 1 may be molded into the
tire sidewall following the letter designat-
ing the tire speed rating (
page 313).
No specification given: absence of any text
(like in above example) indicates a
standard load (SL) tire.
XL or 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”.
iFor illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.

318 Operation
Tires and wheels
1DOT
2Manufacturer’s identification mark
3Tire size
4Tire type code (at the option of the tire
manufacturer)
5Date of manufactureDOT (D
epartment of Transportation)
A tire branding symbol1 (
page 318)
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 318) 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, see (
page 291).
Tire size
The code3 (
page 318) indicates the
tire size.Tire type code
The code4 (
page 318) may, at the
option of the manufacturer, be used as a
descriptive code for identifying significant
characteristics of the tire.
Date of manufacture
The date of manufacture5 (
page 318)
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.
iFor illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.

324 Operation
Tires and wheels
Maximum tire inflation pressure
This number is the greatest amount of air
pressure that should ever be put in the tire
under normal driving conditions.
Normal occupant weight
The number of occupants the vehicle is
designed to seat, multiplied by
68 kilograms (150 lbs).
Occupant distribution
The distribution of occupants in a vehicle
at their designated seating positions.
Production options weight
The combined weight of those installed
regular production options weighing over
5 lbs (2.3 kilograms) in excess of those
standard items which they replace, not
previously considered in curb weight or
accessory weight, including heavy duty
brakes, ride levelers, roof rack, heavy duty
battery, and special trim.PSI (Pounds per square inch)
A standard unit of measure for air pressure
-> bar, kilopascal (kPa).
Recommended tire inflation pressure
The recommended tire inflation pressure is
listed on Tire and Loading Information
placard located on driver’s door B-pillar for
normal driving conditions and provides
best handling, tread life and riding com-
fort. If so equipped, supplemental informa-
tion pertaining to special driving situations
can be found on the tire inflation pressure
label on the inside of the fuel filler flap.
Rim
A metal support for a tire or a tire and tube
assembly upon which the tire beads are
seated.
Sidewall
The portion of a tire between the tread and
the bead.TIN (Tire Identification Number)
Unique identifier which facilitates efforts
by tire manufacturers to notify purchasers
in recall situations or other safety matters
concerning tires and gives purchases the
means to easily identify such tires. The TIN
is comprised of “Manufacturer’s identifica-
tion mark”, “Tire size”, “Tire type code”
and “Date of manufacture”.
Tire load rating
Numerical code associated with the
maximum load a tire can support.
Tire ply composition and material used
This indicates the number of plies or the
number of layers of rubber-coated fabric in
the tire tread and sidewall. Tire manufac-
turers also must indicate the ply materials
in the tire and sidewall, which include
steel, nylon, polyester, and others.

325 Operation
Tires and wheels
Tire speed rating
Part of tire designation; indicates the
speed range for which a tire is approved.
Total load limit
Rated cargo and luggage load plus
68 kilograms (150 lbs) times the vehicle’s
designated seating capacity.
Traction
Force exerted by the vehicle on the road
via the tires. The amount of grip provided.
Tread
The portion of a tire that comes into
contact with the road.
Treadwear indicators
Narrow bands, sometimes called
“wear bars” that show across the tread of
a tire when only
1/16in (1.6 mm) of tread
remains.Uniform Tire Quality Grading Standards
A tire information system that provides
consumers with ratings for a tire’s traction,
temperature and treadwear. Ratings are
determined by tire manufacturers using
government testing procedures. The
ratings are molded into the sidewall of the
tire.
Vehicle maximum load on the tire
Load on an individual tire that is
determined by distributing to each axle its
share of the maximum loaded vehicle
weight and dividing it by two.
Rotating tires
Tire rotation can be performed on vehicles
with tires of the same dimension all
around. If your vehicle is equipped with
tires of the same dimension all around,
tires can be rotated, observing a
front-to-rear rotation pattern that will
maintain the intended rotation (spinning)
direction of the tire (
page 294).
In some cases, such as when your vehicle
is equipped with mixed-size tires (different
tire dimension front vs. rear), tire rotation
is not possible.
Warning!G
Rotate front and rear wheels only if the tires
are of the same dimension.
If your vehicle is equipped with mixed-size
tires (different tire dimensions front vs.
rear), tire rotation is not possible.

329 Operation
Winter driving
Snow chains
Snow chains should only be driven on
snow-covered roads at speeds not to ex-
ceed 30 mph (50 km/h). Remove chains
as soon as possible when driving on roads
without snow. Please observe the following guidelines
when using snow chains:

Use of snow chains is not permissible
with all wheel/tire combinations
(
page 449).

Use snow chains in pairs and on rear
wheels only. Follow the manufacturer’s
mounting instructions.

Only use snow chains that are ap-
proved by Mercedes-Benz. Any autho-
rized Mercedes-Benz Center will be
glad to advise you on this subject.

Use of snow chains may be prohibited
depending on location. Always check
local and state laws before installing
snow chains.

Do not use snow chains on the spare
wheel (
page 453).

Do not use snow chains on wheels with
MOExtended tires* (
page 449).
!When driving with snow chains, always se-
lect setting 1 of the vehicle level control system
(
page 230). Other settings may result in
damage to your vehicle.
!Some tire sizes do not leave adequate clear-
ance for snow chains. To help avoid serious dam-
age to your vehicle or tires, make sure that the
use of snow chains is permissible as specified in
the “Technical data” section of this Operator’s
Manual, see “Rims and tires” (
page 449).
!If snow chains are mounted to the front
wheels, they may scrape against the body or axle
components. The tires or the vehicle could be
damaged as a result.iWhen driving with snow chains, you may
wish to deactivate the ESP® (page 93) before
setting the vehicle in motion. This will improve
the vehicle’s traction.

356 Practical hints
What to do if …
Warning!G
Each tire, including the spare (if provided),
should be checked monthly when cold and
inflated to the inflation pressure recom-
mended by the vehicle manufacturer on the
Tire and Loading Information placard on the
driver’s door B-pillar (
page 294) or, if
available, the tire inflation pressure label on
the inside of the fuel filler flap (
page 279).
If your vehicle has tires of a different size
than the size indicated on the Tire and Load-
ing Information placard or, if available, the
tire inflation pressure label, you should de-
termine the proper tire inflation pressure for
those tires.
As an added safety feature, your vehicle has
been equipped with a tire pressure monitor-
ing system (TPMS) that illuminates a low tire
pressure telltale when one or more of your
tires is significantly underinflated.
Accordingly, when the low tire pressure tell-
tale illuminates, you should stop and check
your tires as soon as possible, and inflate
them to the proper pressure. Driving on a
significantly underinflated tire causes the
tire to overheat and can lead to tire failure.
Underinflation also reduces fuel efficiency
and tire tread life, and may affect the vehi-
cle’s handling and stopping ability. Please
note that the TPMS is not a substitute for
proper tire maintenance, and it is the driv-
er’s responsibility to maintain correct tire
pressure, even if underinflation has not
reached the level to trigger illumination of
the TPMS low tire pressure telltale.USA only:
Your vehicle has also been equipped with a
TPMS malfunction indicator to indicate
when the system is not operating properly.
The TPMS malfunction indicator is com-
bined with the low tire pressure telltale.
When the system detects a malfunction, the
telltale will flash for approximately
one minute and then remain continuously
illuminated. This sequence will continue
upon subsequent vehicle start-ups as long
as the malfunction exists. When the mal-
function indicator is illuminated, the system
may not be able to detect or signal low tire
pressure as intended.
TPMS malfunctions may occur for a variety
of reasons, including the installation of
replacement or alternate tires or wheels on
the vehicle that prevent the TPMS from
functioning properly. Always check the
TPMS malfunction telltale after replacing
one or more tires or wheels on your vehicle
to ensure that the replacement or alternate
tires and wheels allow the TPMS to continue
to function properly.

418 Practical hints
Flat tire
Preparing the vehicle
Prepare the vehicle as described
(
page 417).
Turn spare wheel bracket counter-
clockwise to loosen.
Take the spare wheel out of the trunk
(
page 401).
Removing tensioning straps
(vehicles with 19" spare wheel only)
A 19" spare wheel has two tensioning
straps on it that must both be removed be-
fore mounting the spare wheel.1Buckle
2Clip
Press on both clips 2 simultaneously
to release buckle 1.Lifting the vehicle
Prevent the vehicle from rolling away
by blocking wheels with wheel chocks
(not included) or other sizeable
objects.
When changing wheel on a level
surface:
Place one wheel chock or other
sizeable object in front of and
another wheel chock or sizeable
object behind the wheel that is
diagonally opposite to the wheel
being changed.
Always try lifting the vehicle using the
jack on a level surface. However,
should circumstances require you to do
so on a hill, place a wheel chock or
other sizeable object and the other
wheel chock or sizeable object as
follows:
Place wheel chocks or other size-
able objects on the downhill side
blocking both wheels of the axle not
being worked on.
iThe tensioning straps are shown in red for
illustration purposes. The tensioning straps on
the spare wheel of your vehicle are black.iKeep the tensioning straps in a safe place.
You will need them to store the spare wheel in
the trunk after use (
page 402).

424 Practical hints
Flat tire
Detach the electric air pump.
Stow the electrical plug and the air
hose behind the flap and place the air
pump back in the trunk.
Lowering the vehicle
Lower vehicle by turning crank coun-
terclockwise until the full weight of the
vehicle is resting on the ground.
Pull the jack out of the jack support
tube.1 - 5 Wheel bolts
Tighten the five wheel bolts evenly,
following the diagonal sequence
illustrated (1 to 5), until all bolts
are tight. Observe a tightening torque
of 96 lb-ft (130 Nm).
Warning!G
Follow recommend inflation pressures.
Do not overinflate tires. Overinflating tires
can result in sudden deflation (blowout) be-
cause they are more likely to become punc-
tured or damaged by road debris, potholes,
etc.
Do not underinflate tires. Underinflated tires
wear unevenly, adversely affect handling
and fuel economy, and are more likely to fail
from being overheated.
Do not overload the tires by exceeding the
specified load limit as indicated on the Tire
and Loading Information placard on the
driver’s door B-pillar. Overloading the tires
can overheat them, possibly causing a
blowout. Overloading the tires can also
result in handling or steering problems, or
brake failure.
iThe flat tire may be transported in the trunk
when the retractable hardtop is raised. If avail-
able, use a protective sheet on the spare wheel.
Vehicles with TPMS or Advanced TPMS*:
Do not activate the tire inflation pressure moni-
tor until a full size wheel/tire with functioning
sensor has been placed back into service on the
vehicle.
Warning!G
Have the tightening torque checked after
changing a wheel. The wheels could come
loose if they are not tightened to a torque of
96 lb-ft (130 Nm).


426 Practical hints
Flat tire
Warning!G
In emergency mode, your vehicle’s driving
characteristics are diminished in such situa-
tions as:

driving around curves

while braking

while accelerating rapidly
Therefore, your driving style must be adapt-
ed accordingly. Avoid abrupt steering and
driving maneuvers, as well as driving over
obstacles (road curbs, potholes, or off-road
areas). This is especially important if the ve-
hicle is heavily loaded.
The emergency driving distance that can be
achieved greatly depends on the demands
placed on the vehicle. Depending on speed,
load, driving maneuvers, road conditions,
outside temperature, etc., the distance can
be significantly shorter or, if the vehicle is
driven cautiously, somewhat longer.
Do not continue driving in emergency mode
if

you notice knocking sounds

the vehicle starts to shake

smoke develops and you smell rubber

ESP® is intervening continuously

you notice tears on the tire sidewalls
After driving in emergency mode, you must
have the rims inspected by an authorized
Mercedes-Benz Center to check if they are
suitable for further use. The failed tire must
be replaced in any case.
iWhen replacing individual or all tires on the
vehicle, make sure only matching tires marked
with “MOExtended” are mounted in the size
specified for your vehicle (
page 449).