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TIFFIN MOTORHOMES
Speed Rating—The speed rating denotes the speed at which a tire is designed to be driven for extended
periods of time. The ratings range from 99 miles per hour (mph) to 186 mph. These ratings are listed
below. NOTE: You may not find this information on all tires because it is not required by law.
Letter Rating
*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.
U.S. DOT Tire Identification Number—This begins with the letters "DOT" and indicated that the tire meets all federal
standards. The next two numbers or letters are the plant code where it was manufactured, and the last four numbers
represent the week and year the tire was built. For example, the numbers 3197 means the 31st week of 1997. The other
numbers are marketing codes used at the manufacturer's discretion. This information is used to contact customers if a tire
defect requires a recall.
Tire Ply Composition and Materials Used—The number of plies indicates the number of layers of rubber-coated fabric in
the tire. In general, the greater the number of plies, the more weight a tire can support. Tire manufacturers also must
indicate the materials in the tire, which include steel, nylon, polyester, and others.
Maximum Load Rating—This number indicates the maximum load in kilograms and pounds that can be
carried by the tire.
Maximum Permissible Inflation Pressure—This number is the greatest amount of air pressure that
should ever be put in the tire under normal driving conditions.
–ALLEGRO®
Q
R
S
T
U
H
V
W
Y
!!!
Chapter 13
Speed Rating
ROUTINE MAINTENANCE
99 mph
106 mph
112 mph
118 mph
124 mph
130 mph
149 mph
168* mph
186* mph
13-16
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