Tire Size And Load Rating; Tire Inflation Pressure And Capacity - Jeep 1979 CJ-5 Technical & Service Manual

2H-2 WHEELS AND TIRES
responsible for the characteristic sidewall "bulge" which
makes the tire appear to be underinflated. This is a
normal condition for radial tires. Do not attempt to
reduce this bulge by overinflating the tire. The only way
to be sure a tire is properly inflated is to use an accurate
and reliable tire pressure gauge. Check and adjust in-
flation pressures in accordance with the information
provided in the Tire Inflation Pressure Chart at the end
of this chapter.
BELTS BELTS
BIAS - PLY R A D I A L - PLY BIAS - BELTED
7 0 1 8 9
Fig 2H-1 Types of T i n Construction
TIRE SIZE AND LOAD RATIO
American and metric tire sizes and tire load range
ratings are indicated in the combination of letters and
numbers imprinted on the tire sidewall such as:
P225/75R-15 load range SL, H78-15 load range B, G78-15
load range D and 9.50-16.5 load range D. The load range
rating replaces the ply rating system formerly used to
denote tire load capacity. Original equipment tires used
on Jeep vehicles are available in load range ratings SL,
B, C, and D.
N O T E : The SL bad range rating applied to the
P225/75R-15 metric tire is equivalent to the current load
range B rating.
Conventional size American tires are identified with
numbers only such as 9.50-16.5. These numbers indicate
approximate tire width and rim diameter in inches. For
example, 9.50 represents tire sidewall-to-sidewall width
and 16.5 the nominal wheel rim diameter required.
The newer American tire sizes are based on tire pro-
file ratio and use letter-number combinations such as
H78-15. In this case, letter H represents tire industry
specifications for the load and inflation schedule for
tires in this letter classification. The number 78 in-
dicates tire section height as determined by the ratio of
section height to sidewall-to-sidewall width. Or, height
divided by width equals size or profile ratio. In this case,
the height of an H78 tire is equal to 78 percent of the
width. This formula applies to all profile series tires (fig.
2H-2). The number 15 denotes the wheel rim diameter
required.
Metric size tires also use letter-number combinations
to indicate size and type. For example, with the
P225/75R-15 tire, letter P indicates tire use is for pas-
senger vehicle applications, 225 is the sidewall-to-side-
wall width in millimeters, 75 is the profile ratio (height
equals 75% of width), R indicates radial-ply construction
and 15 the wheel rim diameter required stated in inches.
SIZES SIZES
" 8 3 " PROFILE R A T I O " 7 8 " PROFILE R A T I O
7 0 2 2 3
Fig. 2 1 - 2
lire
Size a i l
Profile
l i t l o
TIRE INFLATION PRESSURE AND CAPACITY
Original equipment tires used on Jeep vehicles are
selected and tested to meet operating requirements
within tire capacity. The recommended load capacities
and inflation pressures for full or reduced load operation
are listed in the Tire Inflation Pressure Chart at the end
of this chapter. This information is also provided in the
owners manual and on a label attached to the interior
surface of the glove box door.
Tire inflation pressures are selected to be compatible
with the load capacity, ride, and handling character-
istics of a specific vehicle. In cases where a slightly
softer ride is preferred, the driver may use reduced load
pressures but must not exceed 55 mph (88 km/h) or
reduced load vehicle capacity.
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