Spray application manual
15 March 2025
Module 15: Weight, balance and tyres
15.4 Weight and balance requirements
Published 24 January 2025 | Last updated 20 January 2025
To determine the most appropriate tyres and inflation pressures the operator needs to know the weight of the tractor with linkage (including nose tank if fitted) or with the trailing sprayer connected.
Steps to check the weight and balance of a tractor and trailer
One: Check the tractor has suitable power for the task
Check the manufacturer’s tractor manual or technical information for the recommended weight to horsepower ratio (or use Table 7 as a guide) to ensure the tractor is suited to the task.
Recommended weight to PTO horsepower
Two: Determine the optimum weight distribution for the tractor with spray rig
Once you have determined the tractor is suitable for the task, check tractor manufacturer’s manual for the recommended weight distribution, or use Table 8 as a guide.
Recommended weight distribution for various tractor types
Alternatively, you may be able to use the information in Table 9 to determine an appropriate weight distribution for the tractor type.
Percentage of weight on the front axle for various tractor types and tasks
Find out more
Further information on tractor ballast can be obtained from Tractor ballasting Hutton & O’Connor (2021) NSW DPI https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0010/1315297/primefact-tractor-ballasting.pdf
Three: Establish the tractor weight per tyre
With the recommended weight distribution at hand, weigh and record all the tractor weights ‘per tyre’ with all tanks empty, boom folded and unfolded, then again with all the tanks full, boom folded and unfolded.
Four: Analyse the results
After weighing the tractor on a ‘per tyre’ basis, the operator can determine if the weight and balance of the tractor can be adjusted to suit existing tyres and inflation pressures, by checking the tyre manufacturer’s recommendations.
If the current tyres are not able to carry appropriate ballast on the tractor or the total weight with the sprayer when full (at the desired spraying and travel speeds), the operator may need to consider purchasing new tyres that will match the tractor’s ideal weight and balance.
It is also useful to double-check the capacity of the tyres fitted to the spray rig to ensure they are suited for the load they will carry at the desired operating speeds, and that they are inflated correctly.
Tip
It is better to put weights on the front or rear of the tractor, rather than water in the tyres to adjust the balance. Wheel weights or linkage weights are also a good option to help balance the tractor.