GMC Terrain: Wheels and Tires / Tire Designations
Tire Size
The following is an example of a
typical passenger vehicle
tire size.

- Passenger (P-Metric) Tire :
The United States version of a
metric tire sizing system. The
letter P as the first character in
the tire size means a passenger
vehicle tire engineered to
standards set by the U.S. Tire
and Rim Association.
- Tire Width : The three-digit
number indicates the tire section
width in millimeters from
sidewall to sidewall.
- Aspect Ratio : A two-digit
number that indicates the tire
height-to-width measurements.
For example, if the tire size
aspect ratio is 60, as shown in
item 3 of the illustration, it would
mean that the tire's sidewall is
60 percent as high as it is wide.
- Construction Code : A letter
code is used to indicate the type
of ply construction in the tire.
The letter R means radial ply
construction; the letter D means
diagonal or bias ply
construction; and the letter B
means belted-bias ply
construction.
- Rim Diameter : Diameter of
the wheel in inches.
- Service Description : These
characters represent the load
index and speed rating of the
tire. The load index represents
the load carrying capacity a tire
is certified to carry. The speed
rating is the maximum speed a
tire is certified to carry a load.
Useful information about a tire is
molded into its sidewall. The
examples show a typical
passenger vehicle tire and a
compact spare tire sidewall.
Passenger (P-Metric) Tire Example
Tire Size : The tire size is a
combination of letters and
numbers used to define a
particular tire's width, height,
aspect ratio, construction type,
and service description...
Air Pressure : The amount of
air inside the tire pressing
outward on each square inch of
the tire. Air pressure is
expressed in kPa (kilopascal)
or psi (pounds per square inch)...
Other information:
To replace one of these bulbs:
Open the hood. See Hood.
Remove the bulb access cap
from the top of the headlamp
assembly by turning it
counterclockwise.
Remove the bulb from the bulb
socket by pinching the tabs on
either side of the bulb and pull
straight out...
For the base level cluster, this light
comes on when the fuel tank is low
on fuel. The light turns off when fuel
is added. If it does not, have the
vehicle serviced.
For the uplevel cluster, this light is
near the fuel gauge and comes on
briefly when the ignition is turned on
as a check to show it is working...