Mercedes-Benz 2007 CLS 550 Operator's Manual page 315

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
i
For illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
314
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 314) indicates
the nominal tire width in mm.
Aspect ratio
The aspect ratio 2 ( page 314) 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.