UNDERSTANDING TIRE SIDE-WALLS INFORMATION & MARKINGS
*For tires with a maximum speed
capability over 149 mph, tire manufacturers sometimes use the letters ZR. For those with a maximum speed capability over 186 mph, tire
manufacturers always use the letters ZR. See Chart Below.
All tires sold in the United
States must meet the size standards for bead shape, width, diameter
and other parameters established by a recognized standardizing
organization. World leaders among such organizations are the
European Tire and Rim Technical Organization (ETRTO) and the U. S.
Tire and Rim Association (T&RA). Both use a partially metric based
system. Virtually all passenger tires on the market today use the
rim and tire sizing, load and inflation system established by these
bodies. All U. S. highway tires must also meet U. S. DOT standards
as indicated by the letters 'D.O.T.' on the sidewall. The several
tire size designations in use today depend on when a vehicle was
manufactured and whether it was domestic or imported. All
tire-sizing systems used today provide information about a tire's
dimensions. Among the most important for proper fitment is height,
width and load carrying capacity.
This is the
United States version of a metric sizing system established in 1976.
P-Metric passenger car tire sizes begin with "P", which simply means
This European tire sizing system is
similar to P-Metric but does not use the "P" designator.
This system was established in 1968 and is based on
the tire's load carrying capacity, correlated to its overall size.
The tire's capacity and size are indicated by letter designations
from "A" (smallest tire, lowest capacity) to "N" (largest tire,
highest capacity). An example of an Alphanumeric tire size is
BR78-13. "B" shows size/load, "R" indicates radial construction,
"78" is the aspect ratio, and "13" is the wheel size in inches.
This is the oldest standardized tire sizing system
for passenger car tires. When this system was adopted, tire aspect
ratios were either 92 or 82. For example, a 7.00-14 tire has a
section width of 7 inches, a rim diameter of 14 inches and an aspect
ratio of 92. The low profile equivalent size tire with an aspect
ratio of 82 would be 7.35-14.**** Example: P215/65R15 89H
P PASSENGER (P-METRIC/NON-P-METRIC)
This indicates a passenger car tire. If the first character in the
size designation is a "P", the tire is a "P-Metric" tire and is
engineered to standards set by the T&RA (Tire and Rim Association).
If there is no "P", the tire is engineered to ETRTO (European Tire
and Rim Technical Organization) standards and is a metric tire. The
standards set by T&RA and ETRTO have evolved together and are
215 SECTION WIDTH
numerals indicate the tire section width in millimeters. This is the
dimension from sidewall to sidewall. A tire's section width will
vary depending on the rim to which it is fitted. The section width
will be larger on a wide rim and smaller on a narrow rim. Therefore,
each tire is measured to specific rim width. (To convert millimeters
into inches, divide by 25.4.)
65 ASPECT RATIO
two-digit number indicates the tire's aspect ratio. It compares the
tire's inflated section height, which is the distance from the bead
to the tread, to its section width (maximum). An aspect ratio of 65
means that the tire's section height is 65% of the tire's section
width. For clarity, the section width in millimeters is separated
from the aspect ratio by a slash (/).
letter indicates the type of ply construction in the tire's casing
or carcass. "R" means radial. "D" means diagonal, referring to bias
ply tires. "B" means belted for belted-bias ply tires. Never mix
radial tires with any other construction on a car.
The "15" indicates the rim diameter in inches. It is the
diameter of the tire bead seat ledge in the rim. Most tires are
built to inch standards for rim diameters. However, some tires are
built to millimetric rim dimensions. Always match the tire's rim
diameter to the wheel rim diameter. This is important for safety.
A millimetric rim has a different shape than an inch
rim; they are not interchangeable.
89H SERVICE DESCRIPTION
The service description is an alphanumeric combination, consisting
of two parts, a number and a letter. In this example �89� is the
load index, which represents the load carrying capacity. (All
passenger car tires in the US are also marked with their actual load
limit in pounds). The letter part is the speed symbol, 'H,' in this
example. This is the maximum speed for which the tire is rated at
the load specified by the load index. In this example, 'H' means
speeds up to 130 mph. Dunlop does not recommend the use of any of
its products in excess of legal speed limits. Speed ratings do not
necessarily imply that the performance (handling and grip) of the
tire meet the performance standards implied by the ratings.. Dunlop
designs tires to provide high performance levels commensurate with
the higher speed ratings.
Tire speed ratings
must exceed the maximum speed capability of the vehicle to which
they are fitted. Not all tires sold in the US are speed rated,
although many modern performance and luxury cars are equipped with
speed rated OE tires. It is important to remember this when
replacing the tires on your vehicle. Do not downgrade speed ratings
from O.E. ratings.
Speed Ratings � where applied are
indicative of high performance characteristics based on European ECE
30 Indoor Wheel testing as performed by Dunlop and are not valid for
damaged, altered, repaired, under-inflated, overloaded, excessively
worn, or re-treaded tires. Dunlop does not recommend the use of any
of its products in excess of legal speed limits.
Some tires carry additional markings related to
service. An M&S or M+S designation means the tire is rated suitable
by the manufacturer for mud and snow use. The guidelines are set by
the Rubber Manufacturers Association (RMA) in the United States.
Is a marking which means that the tire
meets M&S/M+S requirements without the drawbacks of noise and
rolling resistance associated with the traditional deep-lug winter
tires. The M&S/M+S designation means that the tire is suitable for
normal all-weather driving applications. Tires that meet the
requirements of the M& S designation have better winter traction
compared to those without the M&S symbol.
some heavy snow areas, local governments may require true snow
tires, those with very deeply cut tread. These tires should only be
used in pairs or placed on all four wheels. Make sure you purchase
snow tires that are the same size and construction type as the other
tires on your vehicle.
RMA Severe Snow Conditions-Rated
North American tire manufacturers and the Rubber Manufacturers
Association (RMA) have established a voluntary, industry-wide
definition for passenger and light truck tires intended for use in
SEVERE SNOW CONDITIONS. Tires must meet a performance based criteria
feature tread pattern, construction elements and materials which
generally provide snow performance superior to that of tires bearing
the RMA's current M&S Rating. Such tires will display a
The 10 digit DOT (Department
of Transportation) code number molded into the sidewall designates
the manufacturer and plant where the tire was produced, the tire
line and size, and the week and year the tire was manufactured.
All passenger tires are marked on the
sidewalls to indicate maximum load capacity and maximum inflation
pressure. Truck tires will indicate recommended pressure for maximum
loads for both dual and single application.
Red dots on Dunlop high performance tires for match mounting
purposes. This dot marks the 'high spot' of the tire, which is then
matched with the 'low spot' on the rim to cancel out harmonic
FOR LIGHT TRUCK
|Tires for light trucks have other
markings besides those found on the sidewalls of passenger tires.
The "LT" indicates the
tire is for light trucks.Max. Load Dual kg (lbs) at kPa (psi) Cold
This information indicates the maximum load and tire pressure when
the tire is used as a dual, that is, when four tires are put on each
rear axle (a total of six or more tires on the vehicle).
Load Single kg (lbs) at kPa (psi) Cold
This information indicates
the maximum load and tire pressure when the tire is used as a
This information identifies the tire's
load-carrying capabilities and its inflation limits.
|Tire Speed-Rating System
|TIRE ROTATION DIRECTION EXAMPLES
Rotating tires from front to back and from side to side can
reduce irregular wear (for vehicles that have tires that are all the same size).
Look in your owner's manual for information on how frequently the tires on your vehicle should be rotated and the best pattern for rotation.
*For maximum mileage, rotate your tires every 5,000 miles. Follow correct rotation patterns.
RacelineCentral.com All Rights Reserved
Designated trademarks are the property of their respective owners
12/04/19 08:05:44 AM