MASSEY FERGUSON 410 Operators Instruction Book page 87

Cross-ply tires
The term 'cross-ply tires' applies to tires with bias or
diagonal ply fitted to the front two-wheel drive axle
or rear driven wheels. If you are unable to weigh the
tractor axles to determine the correct tire inflation
pressures, the following method can be adopted on
firm surface conditions with correctly ballasted tractors.
In the case of cross-ply tires the procedure is to check
the size and ply rating and refer to load/inflation
charts. For the relevant size read across the chart to
the figure in brackets for the relevant ply rating - the
inflation pressure indicated in the column heading is
the maximum permissible and should be applied in
cases where it is not possible to weigh the axle.
For LOADER application only, front tire pressures
should be increased by 25%. A correctly inflated
cross-ply tire under full load should have the profile
shown in Fig. 130.
Fig.131
Key to Fig. 131.
1. Section width in inches.
2. Radial construction.
3. Rim diameter in inches.
4. Load diameter in inches.
5. Load Index. (Table 8 on page 88)
6. Speed Symbol, A8 = 40 Km/h.(Table9 on page 88)
7. Maximum inflation pressure.
8. Old marking (ply rating).
410/420/430 - 001 8903 U1
UZEL
Maintenance and Adjustment
Load index and speed symbols
In the past the 'tire load capacity category' was
indicated by a PR (Ply Rating) number. This is an
indicator of the tire's carcass strength. Now a code
number is used giving the exact designation of the
load capacity; this is referred to as the Load Index
or LI for short.
In addition to the load index, Speed Index (SI) is
used to designate the 'Speed Category' of the tire.
These two figures will indicate the maximum load
that can be carried by the tire at a prescribed speed.
Understanding the information on the tire side wall
is important. The illustration (Fig. 131) shows a radial
tire.
Example: A single tire with a marking of 18.4 R 30
142 A8 is 18.4 inch wide radial on a 30 inch wheel,
maximum load capacity 2650 kg (5830 lbs) per wheel,
5300 kg (11660 lbs) per axle, maximum speed
40km/hour.
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