About Tires

A.R.M. Enterprises carries most all sizes of passenger car, light truck and Bigrig
tires. 12", 13", 14", 15", 16", 17", 18" 19.5" and 20" rim sizes are available.
We also have 825, 900 and 1000 X 20, LP and 11R 22.5 and 24.5 Bigrig New Recaps

Helping you try to understand about tires and the number collation that is associated
with tire sizes

Guide to Tires

This should cover everything you need to know about tires....

We will start with the basics and then go into the more advanced info.
All of the experts out there should skip to the section called Service
Description.

TIRE IDENTIFICATION

Passenger car tire identification numbers take the following form:
e.g. P215/65R15 95S Where:
P= Passenger Tire
215= Section Width in Millimeters
65= Aspect Ratio (%)
R= Radial Construction
15= Rim Diameter in Inches
95S= Service Description

The section height (sidewall height) can be determined by multiplying the
section width by the aspect ratio. In this example 215 x 65% = 139.75mm

SERVICE DESCRIPTION
The service description is a combination of the load index (95) and
the speed rating (S).

The speed ratings are as follows (Symbol = Max Speed [mph/kph]):
Note: These ratings are the maximum speed that a tire has been certified for,
not necessarily the maximum capacity of the tire.
A1 = 3 / 5
A2 = 6 / 10
A3 = 9 / 15
A4 = 12 / 20
A5 = 16 / 25
A6 = 19 / 30
A7 = 22 / 35
A8 = 25 / 40
B = 31 / 50
C = 37 / 60
D = 40 / 65
E = 43 / 70
F = 50 / 80
G = 56 / 90
J = 62 / 100
K = 68 / 110
L = 75 / 120
M = 81 / 130
N = 87 / 140
P = 94 / 150
Q = 100 / 160
R = 106 / 170
S = 112 / 180
T = 118 / 190
U = 124 / 200
H = 130 / 210
V = 149 / 240
W = 168 / 270
Y = 186 / 300

Two exceptions to this rule... When this rating system was created, the
maximum speed rating was V. Tires that used the old system can be identified
by having the V located within the size description (ie 215/65VR15). These
tires are called Unlimited V and were rated for ABOVE 130 / 210.

Today the Z rating is still used in this fashion (ie 215/65ZR15) and this
means that the tire are rated for ABOVE 149 / 240. These are called
Unlimited Z.

You will sometimes see Z and Y or W on the same tire wall as Y and W were
just added to the lettering system (ie 215/65ZR15 93W). Any tires produced
after these new letters were added and only contain a Z, are rated at ABOVE 186 /
300.

For Unlimited Z and Unlimited V, it is recommended that you contact the tire
manufacturer for maximum certified speed rating and load rating.

Load Capacity

The number in the service description is called the load index. It is the
load capacity at maximum inflation pressure. It is a number between 74 and
150 where 74 is the lowest load capacity and 150 is the highest. We will only
list 74 through 99. If you need to know any higher rating, e-mail us...

Load Index = Load (lbs/kg)
74 = 827 / 375
75 = 853 / 387.5
76 = 882 / 400
77 = 908 / 412.5
78 = 937 / 425
79 = 963 / 437.5
80 = 992 / 450
81 = 1019 / 462.5
82 = 1047 / 475
83 = 1074 / 487.5
84 = 1102 / 500
85 = 1135 / 515
86 = 1168 / 530
87 = 1201 / 545
88 = 1235 / 560
89 = 1279 / 580
90 = 1323 / 600
91 = 1356 / 615
92 = 1389 / 630
93 = 1433 / 650
94 = 1477 / 670
95 = 1521 / 690
96 = 1565 / 710
97 = 1609 / 730
98 = 1653 / 750
99 = 1709 / 775

Uniform Tire Quality Grading System (UTQGS) and Uniform Tire Quality Grade
Labeling (UTQGL).

That is the official name of the three codes that you see on the side of
all tires.
TREADWEAR
TRACTION
TEMPERATURE

Where tires fall in these categories is determined by the manufacturer. The
manufacturer is responsible for testing tires according to a government
described test procedure and then categorizing them according to their
results.

Treadwear:
This code ranges for 60 to 500 in 20-point increments. (As a disclaimer,
manufacturers say that the testing required to arrive at these numbers can
not accurately predict real world driving wear and therefore can not be
correlated with any actual life expectancy in miles/kilometers). Where 60
means the shortest tread life and 500 means the longest.

Testing for this category is performed on a 400 mile test course near San
Angelo, TX , USA. A group of not more than four test vehicles travel the
course in a convoy so that all tires experience the same conditions. Tread
depths are measured every 800 miles. The same procedure is done for a set of
control tires. After 7,200 miles results are compared and the test tires are
assigned a rating.

Traction:
Traction grades are A, B or C. Where A is the best and C is the worst.

Traction is the rating of a tires ability to stop a car in a straight line
motion on a wet test surface. The test only looks at straight line SKIDING
on Concrete and asphalt surfaces. All tests are performed on government skid
pads.

20 measurements are taken on a control tire on an asphalt surface and then
averaged. Then 20 measurements are taken on a control tire on a concrete
surface and then averaged. The test tires follow the same procedure. The
results are compared and the tires a assigned a Traction Grade.

Temperature:
Temperature grades are A, B or C. Where A is the highest and C is the
lowest.

This measurement rates the tire's (manufacturer's disclaimer again: a
properly maintained tire's) ability to dissipate heat under controlled indoor
test wheel conditions.

The test consists of successive 30-minute runs on a bench (industry term for
a simulator) in 5 mph increments starting at 75 mph. These test continue
until the tire fails due to heat build-up. A grade of C, means the tire
meets minimum DOT specifications, while B and A are better than DOT
regulations.

DOT MA L9 ABC 0301
"DOT" means the tires meet or exceed the Department of Transportation's safety
standards. "MA" is the code number assigned by the DOT to the manufacturing plant.
"L9" is the tire size (in this case, P215/65R15). "ABC" is a group of symbols, optional
with the manufacturer to identify the brand or other significant characteristics of the
tire. The "0301" means the tire was made during the 3rd week of 2001 (the first two
numbers designate the week and the last two numbers indicate the year).

If you have any more questions about sizes or measurements of tires, please email us
at: info@armenterprises.com