Transport Pressure:
Tyre manufacturers generally recommend the correct “transport pressure”, which is the term used for the inflation pressure applied for when the machine is travelling on the road. In many cases this pressure is 23PSI — sometimes higher.
Operating on the road is the “number two” killer of tyres, which is impacted significantly by incorrect tyre transport pressure, which is why it is so important to get this right. Tyres set below the appropriate transport pressure will increase their wear rate as they will become subjected to the number one killer of tyres — heat!
There are a number of advantages of inflating to correct transport pressures for the road. These include:
- Tyres will last longer
- You will use less fuel
- There will be decreased chances of an uneven wear pattern, and
- Better stability.
As the definition suggests, transport pressure should only be applied when a machine is travelling on a road. If transport pressure is used in the field, this can cause severe disadvantages such as:
- Higher levels of slip
- Greater rolling resistance
- Compaction
- Rutting
It’s not uncommon to try and compromise on pressures, however this is not advisable as this is the reason approximately 70% of soils are compacted by the movements of agricultural machinery (which is far from an ideal outcome)!
Soil behaves as an elastic medium/body under pressure. The higher the pressure the more ‘plastic’ it becomes. As the soil particles become compressed together, physical, biological, and chemical changes occur which cause the deterioration of the properties of the soil and limit its many beneficial functions. As a result there is:
- Increased erosion
- Increased resistance when working the soil
- Deterioration of water management
- Reduced yield as a result of an impermeable layer.
By working to get the pressure (and wheel setups) right, you are able to increase the contact areas and in doing so provide a better weight distribution of the tractor/implement, while also reducing the incidents of soil compaction. Increasing the contact area leads to a reduction in slip of the wheel, and has the added advantages of improving the vehicle’s performance and reducing fuel consumption.
Operating Pressure:
The reality is that tyre pressure is all that is actually carrying the load! It is also all that is getting your tractor’s performance to the ground. Often when talking about inflation pressure, we hear people generalise that you need between 16-18 PSI, or three to four lugs on the ground. The only way to be sure you get the operating pressure right is to take the air pressure and see if it matches what is recommended for your load and speed.
The advantages of using ‘operating pressure’ (the term used for the pressure level applied on a machine working in the field), include:
- Lower levels of slip
- Higher tractive performance, and
- Preserved soil structure.
Obviously operating pressures should not be used on the road – and if they are, this can cause disadvantages such as:
- Reduced tyre life
- Higher rolling resistance
- Greater fuel consumption
- Tyre failure – due to an inability to carry the load at speed.
When setting up the operating pressures there are a number of factors which should be considered, including where the tractor is operating on inclines of 30 degrees or more. In this type of scenario, a substantial proportion of the load is transferred to the end of the tractor at the bottom. Considering your operating pressures carefully and adjusting as necessary is vital to avoid tyres rolling off rims or premature failure of your tyres.
