Mercedes-Benz SLR McLaren. Operator's Manual.

Operation
Tires and wheels
Tire size designation, load and speed
rating
1 Tire width
2 Aspect ratio in %
3 Radial tire code
4 Rim diameter
5 Tire load rating
6 Tire speed rating
272
i
For illustration purposes only. Actual
data on tires is specific to each vehicle
and may vary from data shown in above
illustration.
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 width 1 ( page 272) indicates
the nominal tire width in mm.
Aspect ratio
The aspect ratio 2 ( page 272) 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 code 3 ( page 272) indicates
the tire construction type. The “R” stands
for radial tire type. Letter “D” means diagonal
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 274).