美国轮辋轮胎协会标准TRA-2008
SECTION 3
INDEX TO TRUCK-BUS SECTION
VEHICLES DESCRIPTION TABLE LOAD/INFL.
PAGE
GENERAL
DATA PAGE
TRUCK-BUS RADIAL PLY TIRES
Trucks, Busses, and Trailers Low Profile Wide Base Metric - 15o Rim TBM-43-073-07 Metric - 15o Rim TBM-2R3-08, 3-103-09, 3-11
Metric - 15o Rim TBM-1R3-123-13 Metric Wide Base - 15o Rim MWB-13-143-14 Metric - 5o Rim TBM-33-153-15 HC Low Platform Trailer - 15o Rim HC-23-163-17 Heavy Duty Truck - 15o Rim TTB-3R3-183-19 Wide Base - 15o Rim WBTB-3R3-203-21 Heavy Duty Truck - 5o Rim TB-3R3-22, 3-243-23, 3-25 Special Bus SB-1R3-26, 3-283-27, 3-29 Load Limits at Various Speeds3-04
Trucks and Trailers
used at Restricted Speeds
Restricted Speed - 5o Rim HTB-3R3-303-31 Load Limits at Various Speeds3-54 TRUCK-BUS DIAGONAL (BIAS) PLY TIRES
Trucks, Busses, and Trailers
Heavy Duty Truck - 15o Rim TTB-3B3-323-33 Wide Base - 15o Rim WBTB-3B3-343-35 Heavy Duty Truck - 5o Rim TB-3B3-36, 3-383-37, 3-39 Special Bus SB-1B3-40, 3-423-41, 3-43 Load Limits at Various Speeds3-04
Trucks and Trailers
used at Restricted Speeds
Restricted Speed - 5o Rim HTB-3B3-443-44 Load Limits at Various Speeds3-54 MOBILE HOME DIAGONAL (BIAS) PLY TIRES
Mobile Home Mobile Home Tires MH-23-453-45
MINING AND LOGGING TIRES
Mining and Logging
Wide Base ML Tires WBTB-3ML3-463-47 Mining and Logging Tires
TB-9ML3-483-49
TB-8MLR3-503-51
TB-8MLB3-523-53
GENERAL
Explanation of Tire Size Designations3-02
Tire Selection and Definition of Terms3-03
Optional Speed Symbols3-05 Load and Inflation Information for Rims and Wheels3-05
Notes to General Data and Load Rating Tables 3-05
Definition of Maximum Grown Tire Envelope 3-06
NOTE: See Section 8 for Rim Contour dimensions.
COLD INFLATION PRESSURES
The inflation pressures shown in this section are those taken with the tires at
the prevailing atmospheric temperatures and do not include any inflation pressure
build-up due to vehicle operation.
DEFINITION OF “NEW TIRE DIMENSIONS” AND “MEASURING PROCEDURE” (SEE PAGES XII AND XIII) DEFINITIONS OF PREFIX AND SUFFIX LETTERS USED IN TIRE SIZE DESIGNATIONS
(SEE PAGES XIV AND XV)
EXPLANATION OF TIRE DESIGNATIONS FOR TRUCK TIRES METRIC SIZE DESIGNATED TIRES
TIRE SIZE DESIGNATION OPTIONAL
LOAD SERVICE
TIRE SIZE DESIGNATION IDENTIFICATION DESCRIPTION 255 / 70 R 22.5 G 138/134 M
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CONSTRUC- SPEED
NOMINAL NOMINAL TION RIM LOAD SYMBOL SECTION ASPECT CODE DIAMETER RANGE LOAD INDEX
WIDTH RATIO “R”-RADIAL CODE (SINGLE/DUAL)
(mm) “D”-DIAGONAL
CONVENTIONAL SIZE DESIGNATED TIRES
10.00 R 20 H 146/143 L
11 R 22.5 H 146/143 L
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NOMINAL CONSTRUCTION RIM LOAD SPEED SECTION CODE DIAMETER RANGE SYMBOL WIDTH “R” - RADIAL CODE
(INCHES) “-”-DIAGONAL LOAD INDEX
(SINGLE/DUAL)
(A ”TR” suffix is part of size designation on the 7.50-15TR, 8.25-15TR, 10.00-15TR
and 11.00-15TR to indicate a tire for rims having a specified rim diameter of
nominal plus .156 inches or plus .250 inches.)
8 R 17.5 HC F 122/120 L
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NOMINAL CONSTRUCTION RIM FOR USE LOAD SPEED
SECTION CODE DIAMETER ON “HC” RANGE SYMBOL WIDTH “R”-RADIAL CODE TYPE LOAD INDEX
(INCHES) RIMS (SINGLE/DUAL)
10.00 R 20 ML F
11 R 22.5 ML F
7 R 14.5 MH E
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NOMINAL CONSTRUCTION RIM LOAD SECTION CODE DIAMETER RANGE
WIDTH “R”-RADIAL CODE
(INCHES) ML - MINING AND LOGGING
MH - MOBILE HOME TIRES
SELECTION OF TIRES FOR TRUCKS, BUSSES, AND TRAILERS
AND DEFINITION OF TERMS
TIRE AND RIM ASSOCIATION STANDARD
TIRE SELECTION
Truck-Bus Tires - Selection of size and load range on each axle shall be based upon the highest individual wheel load.
Maximum load per tire shall not be greater than the applicable load specified herein for the proper load range and usage.
DEFINITIONS OF TERMS
MAXIMUM LOAD - The maximum load on individual tires is to be determined by the manu-facturer of the completed vehicle, and shall include:
a. Curb Weight: Defined as the manufacturer’s weight of the completed vehicle with
standard equipment including cab and/or utility body and the maximum capacity of
engine fuel, oil, and coolant.
b. Driver and Occupant Weight: Defined as 150 pounds per occupant for the vehicle’s
designated seating capacity. For city and city-suburban busses, occupant load is based
on 150 pounds per occupant and 150% of full-seated rating. For intercity busses,
occupant load is based on 185 pounds per occupant (to include luggage) and 100%
full-seated rating.
c. Accessory Weight: Means the combined weight of those installed regular production
options (not previously considered in Curb Weight) weighing five pounds or more. If
such options replace standard items, include only the excess if the excess is over
five pounds.
d.Extra Equipment Weight: Means the weight of any non-standard item other than
accessories, which are affixed to the vehicle.
e. Cargo Load: Consists of weight in the cargo area. Consideration shall be given to all
possible ways the user can load the vehicle approved by the manufacturer, including
uneven loading side to side. The user who loads such vehicles unevenly must be
responsible for reducing the maximum cargo load to prevent overloading any tires. For
intercity busses, the maximum cargo load must also be included in addition to the
occupant load in determining maximum tire load.
COLD INFLATION PRESSURES - The inflation pressures shown in this section are those
taken with the tires at the prevailing atmospheric temperatures and do not include any
inflation pressure build-up due to vehicle operation.
RIM SELECTION
See Page 8-03
NOTES ON TIRE SELECTION
1: The selection of tire sizes shall be based on meeting the requirements of maximum load as defined above. Maximum load as defined above must not exceed the maximum tire
load limit indicated by the bold face type in the table. Minimum recommended cold inflation
pressures for various loads must conform to the load table.
2: IMPROVED SURFACE - An improved surface is one, which is relatively smooth and intended to handle any vehicle manufactured primarily for use on the public streets, roads
and highways.
TRUCK-BUS TIRES USED ON IMPROVED SURFACES
LOAD LIMITS AT VARIOUS SPEEDS FOR DIAGONAL AND RADIAL PLY TIRES
TIRE AND RIM ASSOCIATION STANDARD
(These Tables apply to tires only.
Consult rim/wheel manufacturer for rim/wheel load and inflation capacities.)
FOR METRIC AND WIDE BASE TIRES
Shown in Table TBM-1R, TBM-2R, WBTB-3R, WBTB-3B and MWB-1
SPEED RANGE
(MPH)RADIAL PLY TIRES
DIAGONAL (BIAS) PLY TIRES
% LOAD CHANGE
INFL. PRESSURE
CHANGE
% LOAD CHANGE
INFL. PRESSURE
CHANGE
71 thru 75 1)-12%+ 5 psi -12%+ 10 psi 66 thru 70 1)-4%+ 5 psi -4%+ 10 psi 51 thru 65None No increase None No increase 41 thru 50+7%No increase +7%No increase 31 thru 40+9%No increase +9%No increase 21 thru 30+12%+10 psi +12%No increase 11 thru 20+17%+15 psi +17%No increase 6 thru 10+25%+20 psi +25%No increase 2.6 thru 5+45%+20 psi +45%No increase Creep thru 2.5+55%+20 psi +55%No increase Creep 3)+75%+30 psi +75%+10 psi Stationary
+105%+30 psi
+105%+10 psI
SPEED RANGE
(MPH)RADIAL PLY TIRES
DIAGONAL (BIAS) PLY TIRES
% LOAD CHANGE
INFL. PRESSURE
CHANGE
% LOAD CHANGE
INFL. PRESSURE
CHANGE
71 thru 75 1)-12%+ 5 psi -12%+ 10 psi 66 thru 70 1)-4%+ 5 psi -4%+ 10 psi 51 thru 65None No increase None No increase 41 thru 50+9%No increase +9%No increase 31 thru 40+16%No increase +16%No increase 21 thru 30+24%+10 psi +24%No increase 11 thru 20+32%+15 psi +32%No increase 6 thru 10 2)+60%+30 psi +60%+10 psi 2.6 thru 5 2)+85%+30 psi +85%+10 psi Creep thru 2.5 2)
+115%+30 psi +115%+10 psi Creep 2) 3)+140%+40 psi +160%+20 psi Stationary 2)
+185%+40 psi
+210%+20 psi
1) These load and inflation changes are only required when exceeding the tire manufacturer’s
rated speed for the tire. 2) Apply these increases to Dual Loads and Inflation Pressures. 3) Creep - Motion for not over 200 feet in a 30-minute period. Note 1: The inflation pressures shown in the referenced tables are minimum cold pressures for the various loads listed. Higher pressures should be used as follows: A: When required by the above speed/load table. B: When higher pressures are desirable to obtain improved operating performance. For speeds above 20 mph, the combined increases of A and B should not exceed 20 psi above the inflation specified for the maximum load of the tire. 2: Load limits at various speeds for: Tires Used in Highway Service at Restricted Speed (Tables HTB-3B & 3R) -See page 3-54. Mining and Logging Tires used in Intermittent Highway Service (Tables TB-8MLR, TB-8MLB, TB-9ML and WBTB-3ML) - See page 3-54. THE MAXIMUM LOAD AND INFLATION CAPACITY OF THE RIM MUST NOT BE EXCEEDED. SEE NOTES ON PAGE 3-05.
FOR CONVENTIONAL TIRES
Shown in Tables TB-3R, TB-3B, TTB-3R, TTB-3B, HC-2, TBM-3, and SB-1R, SB-1B (Inter-city)
DEFINITIONS AND OPTIONAL SPEED SYMBOLS
FOR TRUCK-BUS TIRES
TIRE AND RIM ASSOCIATION STANDARD SERVICE DESCRIPTION DESIGNATED TIRES
DEFINITIONS
Speed Category - A category assigned to a tire, which denotes the maximum speed for which the use of the tire is rated.
Speed Symbol - A symbol indicating the speed category at which the tire can carry a load corresponding to its Load Index under specified service conditions.
Load Index - A numerical code associated with the maximum load a tire can carry at the speed indicated by its Speed Symbol under specified service conditions.
Service Description - A service designation, which is distinct from the size designation,consisting of the Load Index (Single Load/Dual Load, where applicable) and Speed Symbol.
EXAMPLE: 225/70R19.5 121/119 L
RIM AND WHEEL LOAD INFORMATION
IMPORTANT - Rim dimensions are standarized by the Tire and Rim Association for size and contour only, and particular tire and rim combinations are designated to assure proper mounting and fit of the tire to the rim. The load and cold inflation pressure imposed on the rim or wheel must not exceed the rim and wheel manufacturer’s recommendation, even though the tire may be approved for a higher load or inflation. Rims and wheels may be identified (stamped) with a maximum load and maximum cold inflation rating. For rims and wheels not so identified or for service conditions exceeding the rated capacity, consult the rim and wheel manufacturer to determine rim and wheel capacity for the intended service.
See page 8-03 for other rim selection information.
NOTES TO GENERAL DATA TABLES
1. Maximum grown tire in service dimensions are for use by vehicle manufacturers in designing
for tire clearances.
2. When chains are used on tires, additional spacing beyond the Minimum Dual Spacing
dimensions may be required.
3. Minimum Size Factor dimensions are based on the highway tread and design rim width.
4. New tire section widths and overall widths will change 0.1 inch (2.5 mm) for each 1/4 inch
change in rim width. Minimum Dual Spacing should be adjusted accordingly.
NOTE TO LOAD TABLES
1. Minimum cold inflation pressures shall be as indicated in the table for the corresponding loads.
SPEED SYMBOL
SPEED CATEGORY F 80 km/h (50 mph)G 90 km/h (55 mph)J 100 km/h (62 mph)K 110 km/h (68 mph)L
120 km/h (75 mph)
DEFINITION OF MAXIMUM ENVELOPE DIMENSIONS FOR GROWN TIRES
IN SERVICE FOR USE BY VEHICLE MANUFACTURERS
IN DESIGNING FOR TIRE CLEARANCES TIRE AND RIM ASSOCIATION STANDARD
A = 45% Maximum grown section height
B = 80% Design section width - other than Traction Tread tires
B 1 = 90% Design section width - Traction Tread tires
C = Design rim width for 50 Flat Base rim tires = Design rim width + 1.00 for 150 rim tires R 1 = 175% Maximum grown overall width R 2 = Fits between P 1 and P 2 with radius center on 45% maximum grown section height reference line R 3 = Same as R 2 except using P 2 and P 3 NOTE: Radial ply and diagonal (bias) ply maximum grown tire dimensions may be