Get Wheels and tires -> Definition of terms for tires and loading Guide for Mercedes A Class 4 Door Third Generation (2018-2026)

Wheels and tires

309

All-wweather tires and winter tires

"C", "D", "E": a load range that depends on the

maximum load that the tire can carry at a cer-

tain pressure

Index

Speed rating

Index

Speed rating

ZR...Y¹

ZR...(..Y)¹

ZR¹

up to 186 mph (300 km/h)

over 186 mph (300 km/h)

over 149 mph (240 km/h)

Q M+S²

T M+S²

H M+S²

V M+S²

up to 100 mph (160 km/h)

up to 118 mph (190 km/h)

up to 130 mph (210 km/h)

up to 149 mph (240 km/h)

Deꢀnitiion of terms for tires and loading

Tire structure and characteristics: describes the

number of layers or the number of rubber-coated

belts in the tire contact surface and the tire wall.

These are made of steel, nylon, polyester and

other materials.

Specifying the speed rating as the "ZR" index

in tire code 4 is optional for tires up to

186 mph (300 km/h).

Winter tires bear the i snowꢁake symbol and

fulꢀll the requirements of the Rubber Manufactur-

ers Association (RMA) and the Rubber Association

of Canada (RAC) regarding the tire traction on

snow.

If your tire code 4 includes "ZR" and there is

no speed rating 7, ꢀnd out what the maxi-

mum speed is from the tire manufacturer.

Bar: metric unit for tire pressure. 14.5038 pounds

per square inch (psi) and 100 kilopascal (kPa) is

the equivalent of one bar.

If load-bearing index 6 and speed rating 7

are in brackets, the maximum speed rating of

your tire is above 186 mph (300 km/h). To

ꢀnd out the maximum speed, ask the tire man-

ufacturer.

DOT (Department of Transportation): DOT-marked

tires fulꢀll the requirements of the

US Department of Transportation.

Load index 8:

No speciꢀcation given: standard load (SL) tire

Average weight of the vehicle occupants: the

number of vehicle occupants for which the vehicle

is designed, multiplied by 150 lb (68 kg).

"XL" or "Extra Load": extra load tire or rein-

forced tire

"Light Load": light load tire

Uniform Tire Quality Gradding Standards: a uniform

standard to grade the quality of tires with regard

"ZR" stated in the tire code.

Or "M+Si" for winter tires.

Wheels and tires

310

to tread quality, tire traction and temperature

characteristics. The quality grading assessment is

made by the manufacturer following speciꢀcations load on an axle must never exceed the gross axle

GAWR (Gross Axle Weight Rating): the GAWR is

the maximum permissible axle load. The actual

Maximuum weight of the laden vehicle: the maxi-

mum weight is the sum of the curb weight of the

vehicle, the weight of the accessories, the maxi-

mum load and the weight of optional equipment

installed at the factory.

from the U.S. government. The quality grade of a

tire is imprinted on the side wall of the tire.

weight rating. The gross axle weight rating can be

found on the vehicle identiꢀcation plate on the

B‑pillar on the driver's side.

Recommended tire pressure: the recommended

tire pressure is the tire pressure speciꢀed for the

tires mounted to the vehicle at the factory.

Kilopasccal (kPa):: metric unit for tire pressure.

6.9 kPa corresponds to 1 psi. Another unit for tire

pressure is bar. 100 kilopascal (kPa) equals 1 bar.

Speed rating: the speed rating is part of the tire

identiꢀcation. It speciꢀes the speed range for

which a tire is approved.

The tire and information table contains the recom-

mended tire pressures for cold tires, the maxi-

Load index: in addition to the load-bearing index,

the load index may also be imprinted on the side

GVW (Gross Vehicle Weight): the gross vehicle

mum permissible load and the maximum permissi- weight comprises the weight of the vehicle includ- wall of the tire. This speciꢀes the load-bearing

ble vehicle speed.

ing fuel, tools, the spare wheel, accessories instal- capacity of the tire more precisely.

led, occupants, luggage and the trailer drawbar

The tire pressure table contains the recommen-

ded tire pressures for cold tires under various

operating conditions, i.e. loading and/or speed of

the vehicle.

Curb weight: the weight of a vehicle with standard

noseweight, if applicable. The gross vehicle weight

must not exceed the gross vehicle weight rating

GVWR as speciꢀed on the vehicle identiꢀcation

plate on the B‑pillar on the driver's side.

equipment including the maximum capacity of

fuel, oil and coolant. It also includes the air condi-

tioning system and optional equipment if these

are installed on the vehicle, but does not include

Increased vehicle weight due to optional equip-

ment: the combined weight of all standard and

optional equipment available for the vehicle,

regardless of whether it is actually installed on the

vehicle or not.

GVWR (Gross Vehicle Weight Rating): the GVWR is passengers or luggage.

the maximum permitted gross weight of the fully

Maximuum tire load: the maximum tire load is the

maximum permissible weight in kilograms or lbs

for which a tire is approved.

laden vehicle (weight of the vehicle including all

accessories, occupants, fuel, luggage and the

trailer drawbar noseweight if applicable). The

gross vehicle weight rating is speciꢀed on the

vehicle identiꢀcation plate on the B‑pillar on the

driver's side.

Rim: the part of the wheel on which the tire is

installed.

Maximuum permissible tire pressure: maximum

permissible tire pressure for one tire.

Wheels and tires

311

Maximum lload on onne tire: maximum load on one

tire. This is calculated by dividing the maximum

axle load of one axle by two.

Side wall: the part of the tire between the tread

and the tire bead.

tire tread is level with the bars, the wear limit of

1/16 in (1.6 mm) has been reached.

Weight of optional equipment: the combined

weight of the optional equipment weighing more

than the replaced standard parts and more than

5 lbs (2.3 kg). This optional equipment, such as

high-performance brakes, level control system, a

roof luggage rack or high-performance batteries,

is not included in the curb weight and the weight

of the accessories.

Distribution of vehicle occupants: distribution of

vehicle occupants over designated seat positions

in a vehicle.

PSI (poundds per square inch): standard unit of

measurement for tire pressure.

Aspect ratio: ratio between tire height and tire

width in percent.

Maximum permissible payload weight: nominal

load and luggage load plus 150 lb (68 kg) multi-

plied by the number of seats in the vehicle.

Tire pressuure: pressure inside the tire applying an

outward force to every square inch of the tire. The

tire pressure is speciꢀed in pounds per square

inch (psi), in kilopascals (kPa) or in bar. The tire

pressure should only be corrected when the tires

are cold.

Changing a wheel

TIN (Tire Identiꢀcatioon Number): a unique identiꢀ-

cation number which can be used by a tire manu-

facturer to identify tires, for example, in a product

recall, and thus identify the purchasers. The TIN is

made up of the manufacturer's identity code, tire

size, tire type code and the manufacturing date.

Notes on selecting, installing and replaacing tires

NOTE Mercedes-AMG vehicles

Cold tire pressure: the tires are cold when the

vehicle has been parked for at least 3 hours with-

out direct sunlight on the tires or the vehicle has

been driven for less than 1 mile (1.6 km).

Observe the notes in the Supplement.

You could otherwise fail to recognize

dangers.

Load-bearing index: the load-bearing index is a

code that contains the maximum load-bearing

capacity of a tire.

Tire contact surface: the part of the tire that

comes into contact with the road.

WARNING Risk of accident due to incor-

rect wheel and tire dimensions

Traction: traction is the grip resulting from friction

between the tires and the road surface.

Tire bead: the purpose of the tire bead is to

ensure that the tire sits securely on the wheel rim.

There are several wire cores in the tire bead to

prevent the tire from changing length on the

wheel rim.

If wheels and tires of the wrong size are instal-

led, the service brakes or components in the

Wear indicator: narrow bars (tread wear bars) that

are distributed over the tire contact surface. If the

Wheels and tires -> Definition of terms for tires and loading for Your Mercedes A Class 4 Door Third Generation (2018-2026)

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