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3.2.8 Selecting the Optimal Inner Pressure in Tyres Depending on Operation
Conditions and Load on the Tractor Axis, Tyres Operation Rules
3.2.8.1 Selecting the optimal inner pressure in tyres depending on operation condi-
tions and load on the tractor axis
Selection of the optimal inner pressure in tyres of the wheeled tractor and extent of
its influence on the towing and hitching properties depends on the work type, soil type and
load on the tractor axis. Air pressure in tyres effects on the wheel supporting contact spot
on soil and depending on the soil conditions has an influence on the towing and hitching
properties and the tractor productivity in operation. Nominal values for the tyres loads to
select work mode under various inner pressures and speeds are established by the tyres
manufacturer and specified in Table 3.2.3.
Pressure value depends on the movement speed and weight load on the tractor
tyres, which are transmitted from the hitched machines taking into account own operation-
al weight of the tractor and ballast weight, as well as the operation conditions.
Inner pressure in tyres varies for each specific case of the tractor hitching. There-
fore, if the tractor operation conditions have changed, the tyre pressure value shall be
checked and adjusted if necessary. If nominal pressures are not observed, the tyres ser-
vice life will be greatly reduced.
The tractor operation with tyres pressure below nominal value will lead to following
wheels malfunctions:
- tyres slipping on rims;
- tyre bead rubbing against the rim shoulder;
- cracks in the tyre walls;
- lamination or breaking of the tyre casing;
- tearing the tyre valve out (in case of tubed tyres).
The operation with tyres pressure above nominal value will lead to following wheels
malfunctions:
- noticeable increased wear of tyres;
- casing ply stretching and the tyres elasticity decrease;
- increased wheels slipping;
- increased sensitivity to hits and cuts.
Operation with overload, which is exceeding the tyres maximum capacity (for par-
ticular pressure and speed) and tractor axis is the cause of failures and damages not only
to the undercarriage (tyres casing tearing etc.), but to the other tractor units and parts as
well, which can also lead to accidents and the tractor service life shortening altogether.
ATTENTION: ALWAYS SET THE TYRE PRESSURE TAKING INTO ACCOUNT
LOADS AND SPEEDS OF PERFORMED TYPE OF WORK!
Pressure in tyres can be correctly selected and necessity for the ballast weight in-
stallation, ballast mass and type can be determined only after estimating the load on the
tractor axis.
Exact load value for specific case of the tractor usage, which is applied to the tractor
rear or front wheels, can be determined only by actual weighting the tractor with hitched
machine.
Method for the tractor front and rear wheels load determining by weighting is de-
scribed in section 4 "Hitching".
86
921.6-0000010 OM
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