Mounting tyres on four wheel drive tractors

The mounting of tyres on a four wheel drive tractor must be done with great care in order to produce the best driving results and maintain the tyres’ service life. Generally, the actual rolling circumference (R.C.) of a front tyre should be 1 – 3 % (lug pattern max 4%) higher than the rolling circumference calculated using the gear ratio. Excessive positive lead in the front tyres can cause quick wear and reduce mileage, while insufficient lead in the front tyres will make the tractor more difficult to steer. Check the manual of the tractor in question for detailed instructions on the calculation of rolling circumferences (gear ratio). When changing the tyre size or type, always check the relationship between the rolling circumferences and make sure that the combination is within the limits given by the manufacturer.

Example of the calculation:

The basis for the calculation is the gear ratio between the front and rear axle, with which the rolling circumference of the required front tyre can be calculated.

Mounting example

CALCULATING THE ROLLING CIRCUMFERENCE OF FRONT TYRES

Front axle lead (%) calculation