Summer Tires - Mercedes-Benz GLA 250 2019 Operator's Manual

If "LT" precedes the size description: these are
light truck tires according to U.S. manufactur-
ing standards.
If "T" precedes the size description: compact
emergency wheels with high tire pressure that
are only designed for temporary use in an
emergency.
Tire width: tire width : shows the nominal
tire width in millimeters.
Aspect ratio: aspect ratio ; is the size ratio
between the tire height and tire width and is
shown in percent. The aspect ratio is calcula-
ted by dividing the tire width by the tire height.
Tire code: tire code = specifies the tire type.
"R" represents radial tires; "D" represents
diagonal tires; "B" represents diagonal radial
tires.
Optionally, tires with a maximum speed of over
149 mph (240 km/h) may have "ZR" in the
size description, depending on the manufac-
turer (e.g. 245/40 ZR 18).
Rim diameter: rim diameter ? is the diame-
ter of the bead seat, not the diameter of the
rim flange. The rim diameter is specified in
inches (in).
Load-bearing index: load-bearing index A is
a numerical code that specifies the maximum
load-bearing capacity of a tire.
Do not overload the tires by exceeding the
specified load limit. The maximum permissible
load can be found on the vehicle's Tire and
Loading Information placard on the B-pillar on
the driver's side ( page 316).
Y
Example:
Load-bearing index 91 indicates a maximum
load of 1,356 lb (615 kg) that the tires can
bear. For further information on the maximum
tire load in kilograms and lbs, see
( page 322).
Y
For further information on the load bearing
index, see "Load index" (
Speed rating: speed rating B specifies the
approved maximum speed of the tire.
i
Tire data is vehicle-specific and may devi-
ate from the data in the example.
Regardless of the speed rating, always observe
the speed limits. Drive carefully and adapt
your driving style to the traffic conditions.
page 322).
Y
All about wheels and tires

Summer tires

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)
ZR...Y up to 186 mph (300 km/h)
ZR...(..Y) over 186 mph (300 km/h)
ZR over 149 mph (240 km/h)
Optionally, tires with a maximum speed of
R
over 149 mph (240 km/h) may have "ZR" in
the size description, depending on the man-
ufacturer (e.g. 245/40 ZR18).
The service specification is made up of load-
bearing index A and speed rating B.
If the size description of your tire includes
R
"ZR" and there are no service specifications,
ask the tire manufacturer in order to find
out the maximum speed.
If a service specification is available, the
maximum speed is limited according to the
speed rating in the service specification.
Example: 245/40 ZR18 97 Y. In this exam-
ple, "97 Y" is the service specification. The
letter "Y" represents the speed rating. The
maximum speed of the tire is limited to
186 mph (300 km/h).
The size description for all tires with maxi-
R
mum speeds of over 186 mph (300 km/h)
must include "ZR" and the service specifica-
tion must be given in parentheses. Example:
275/40 ZR 18 (99 Y). Speed rating "(Y)"
indicates that the maximum speed of the
tire is over 186 mph (300 km/h). Ask the
tire manufacturer about the maximum
speed.
321
Z