upon appearance of tire for inflation test.
(1) Do not place semitrailers in the sun for long periods,
tires. If possible, park semitrailer under cover to pro-
tect it from sun, sand, and dust.
Cover inactive semitrailers
suitable shelter is available.
(3) Correct tire inflation pressure (par. 52).
(4) Semitrailers that are inactive for long periods in hot,
humid weather are subject to rapid rusting and ac-
tions and clean and lubricate to prevent deterioration.
(5) The canvas paulin should not be exposed to the direct
rays of the sun, unless unavoidable.
Operation on Unusual Terrain and Fording
a . Sand.
For emergency operations in beach and desert sand,
reduce tire inflation. For continued operations in sand,
o v e r s i z e balloon sand tires are necessary for all wheeled
The tread should be of plain rib and the
tire of round cross section, as a tire with deeply cor-
rugated tread (snow tread) or with a raised flat tread
will break through the crust and dig into soft sand
beneath, thereby stopping the vehicle and requiring it
to be dug out.
Operation under extremely sandy or dusty conditions
necessitates frequent inspection, cleaning, and lubrica-
tion of the semitrailer working parts.
Caution: When packing wheel bearings, it is neces-
packing with grease, since sand or dust mixed with
the grease forms an abrasive mixture.
(3) Reducing tire pressures will aid in amphibious land-
ings and in operation in soft sand.
Note. Normal operating tire pressure is 50 psi. For operation
on coral, mud, and snow, reduce tire pressure 60 percent of normal
psi; for ice or soft sand, reduce tire pressure 30 percent of normal
psi; and for beach sand or sand dunes, reduce the tire pressure 25
percent of normal psi. Reduced pressure gives added flotation but
normal pressure must be restored as soon as normal terrain is
reached, otherwise excessive wear or damage to the tire will result.
b. Rocks and Boulders.