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3.2.8 Selection of optimal inner pressure in tires depending on operational
conditions and load on tractor axles, instructions for use of tires
3.2.8.1 Selection of optimal inner pressure in tires depending on operational condi-
tions and load on tractor axles.
Selection of optimal air pressure in tires of wheeled tractors and rate of its influence
on towing and gripping abilities depend on soil type and load applied to tractor axles. Air
pressure in tires influences the wheel-to-soil contact patch and, depending on soil condi-
tions, affects its towing and gripping abilities as well as tractor operational performance.
Rates of loads on tires for selecting the operation mode at various inner pressures and
speeds are set forth by the tire manufacturer and are provided in table 3.2.3.
The pressure value depends on travel speed and weight loads on tractor axles,
caused by weight of coupled implements with due account for tractor own weight and bal-
last weight and also operation conditions.
Inner pressure in tires is different for each specific case of tractor coupling with im-
plements. Therefore, if tractor operational conditions are changed, it is required to check
and if necessary adjust pressure value in tires. Failure to comply with pressure rates de-
creases tire life significantly.
Tractor operation with tire pressure set below the required rate results in the follow-
ing wheel failures:
- tire turning against rims;
- wearing of tire bead against rim edge;
- cracks on tire sidewalls;
- ply separation or rupture of tire carcass;
- tear-out of tire valve (for tubed tires);
Operation with tire pressure higher than the rated pressure results in the following
wheel failures:
- noticeable increased wear of tires;
- stretching of carcass plies and decrease of tire flexibility;
- increased slipping of wheels;
- increased sensitivity to impacts and cuts.
Extra duty operation – i.e. excess of max. load capacity of tires (for given pressure
and speed) and tractor axles – is a reason for failures and damages not only to the under-
carriage (tire carcass rupture, etc.) but also to other units and parts of the tractor, which
can lead to accidents and decrease of the tractor life span in general.
ATTENTION: ALWAYS SET TIRE PRESSURE WITH DUE ACCOUNT FOR
LOADS AND SPEEDS EFFECTIVE FOR THE KIND OF OPERATION BEING CARRIED
OUT!
IT IS PROHIBITED PARK THE TRACTOR FOR A LONG PERIOD OF TIME AND
TO OPERATE IT ON DAMAGED OR DEFLATED TIRES.
Correct selecting of tire pressure as well as identifying if it is necessary to mount
ballast weights, determining the mass and type of necessary weights is possible only after
defining the value of load on tractor axles.
The exact load value for a specific case of tractor use, which is applied to front and
rear wheels of the tractor, can be determined only by way of practical weighing the tractor
with the implement coupled.
To check tire pressure, use manometer under GOST 9921-81 with a scale of 50
kPa to 300 kPa with a division of not more than 10 kPa.
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