Tractor stability
Your tractor’s centre of gravity is important when it comes to keeping your tractor upright and not on its side. Think of it as the machine's balance point, if you let it go past where the wheels touch the ground you are tipping over — there is a strong chance of injury or death. A good day’s work depends on your tractor staying stable.
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The centre of gravity keeps your tractor stable
The centre of gravity is the spot where the tractor's weight is perfectly balanced. The centre of gravity will move as attachments and ballast are added or removed from the tractor.
Fitting a front-end loader, for example, will move the centre of gravity forward to the front wheels and lifting a load will raise the centre of gravity.
Prevent the tractor tipping by keeping the centre of gravity within the tractor's base of stability, which is the area between the wheels.
An unbalanced load may cause the tractor to tip over.
Longitudinal tractor stability is shown in figure 1, as 3 scenarios:
- tipping over forwards
- balanced
- tipping over backwards.
A tractor is stable when the weight is balanced evenly over the front and rear wheels. When an attachment or load is connected to the front of the tractor, it can shift the centre of gravity forward toward the front wheels causing the tractor to become unstable, reducing the effectiveness of the rear brakes, and making the steering heavy.
If the size of the attachment and weight of the load exceeds the manufacturers limits, it can cause the tractor to tip forward. Similarly, when an attachment or load is connected to the rear 3-point linkage, the centre of gravity moves backwards towards the rear wheels. This can reduce the effectiveness of the steering wheels causing the driver to lose control. If the attachment and load exceed the manufacturers limits, the tractor is at risk of tipping backwards.
Review your manufacturer manuals or speak with your tractor and implement retailer to understand the centre of gravity on your tractor.
Use weight to keep your tractor stable
Stability
Heavy loads, like those lifted with a front-end loader, can tip the tractor forward. Similarly, a heavy load on the rear 3-point linkage can tip the tractor backward. Tractors can also tip sideways on uneven terrain.
Consider where your load is and add weight that creates a counteracting force that keeps the wheels on the ground, and your tractor stable.
Tractor safety
A stable tractor will reduce the risk of tipping over, particularly on slopes or uneven terrain.
Operator safety
A stable tractor reduces the need for constant, erratic corrections during driving — a major source of stress and fatigue for operators.
Tractor efficiency
A stable tractor reduces wheel slip by ensuring proper weight distribution. This improves traction and makes better use of the engine's power, reducing fuel consumption and improving performance.
How to use ballast (weight) to keep a tractor stable
Check your tractor manufacturer’s ballasting guidelines before you start ballasting.
Most manufacturers have guidelines and weight calculator tools available on their websites.
It’s best to look at the weight calculator specific to your tractor, because generic weight calculators can be misleading and may not include specific information related to the make and model of your tractor. Each tractor model will have different safe operating limits, including maximum tractor mass, axle limits and how much ballast can be added.
- Wheel weights
Wheel weights are one way of keeping a tractor stable and are often readily available. Attaching manufacturer recommended wheel weights to the rear wheels (figure 2) adds significant weight directly over the axle.
Wheel weights are heavy and fitting these is likely to result in the application of high force and an awkward posture and may require the use of a mechanical aid to install them safely. Follow manufacturers recommendations for fitting and removing them.
Hazardous manual handling is the biggest cause of injuries in Victorian workplaces. Identify hazardous manual handling in your workplace to get a job done right and safely.
Figure 2: A cabin tractor with wheel weights installed to the rear wheels.
Review your manufacturer manuals or speak with your tractor/implement retailer to understand if wheel weights are the right choice for your tractor.
- Implements, weight boxes and tractor weights
Weights can be added to the front or rear of a tractor for stability. This could include a weight box, suitcase weights, heavy implements, or other tractor weights.
Weights can be attached to the front of the tractor using a weight carrier or a 3-point linkage. Weights on the rear of the tractor are typically attached using a 3-point linkage.
Commercially manufactured weights can be more compact because they use high-density cast materials. These can reduce the size of the weight and reduce the chance of collisions with structures when reversing and turning.
Be aware when using a weight box — it can be difficult to know how heavy the ballast is. This is because it depends on what you put inside the box.
Many farmers have access to scales and weigh bridges which can be used to check that the tractor is correctly balanced before use. Or you could calculate the weight of the weight box by using the volume of the box and the density of the material in it.
Figure 3: Commercially manufactured weights installed to tractors.
Figure 3 shows examples of commercially manufactured weights installed to tractors. The first tractor shows multiple suitcase weights installed to a weight carrier on the front of a cabin tractor. The inset image shows the centre of gravity (COG) moving forward. The second tractor shows a counterweight installed to the rear 3-point linkage of a cabin tractor with front end loader. The inset image shows the COG moving back towards the centre of the tractor.
Review your manufacturer manuals or speak with your tractor/ implement retailer to understand if commercial counterweights are the right choice for your tractor.
- Liquid ballast
Using a liquid ballast isn’t recommended by some manufacturers, especially when using radial tyres – best to check your tractors manual first.
Filling the rear tyres with a liquid like water, with or without anti-freeze, provides a low-cost, low-mounted weight that can improve stability and traction.
View more information from the NSW Government on Tractor ballasting (PDF).
Match the implement to the tractor to reduce tipping
Tractor stability and safety will be compromised when using attachments that are too large or heavy for your tractor’s capabilities.
Check the manual
When you are checking the operator's manuals and online tools for both the tractor and the attachment to ensure they are compatible. It’s a good idea to check for things like:
- carrying capacity
- horsepower and hydraulic flow requirements
- the 3-point linkage lift capacity
- drawbar towing capacity
- attachment weight
- trailer brake requirements.
Don’t exceed weight limits
Know your tractor’s maximum operating weight limit, as well as maximum capacities for the front and rear axles and front and rear tyres.
Operating over the weight limits can not only cause a loss of control but also damage the frame, hydraulics, and tyres.
Exceeding the weight limits can also impact the tractors braking capacity and the Roll-Over Protective Structure (ROPS) capacity to protect the operator in a rollover. Make sure you refer to the operator's manual to understand what these limits are.
Liquid loads
When an attachment contains a liquid load the movement of the liquid can reduce the stability of the tractor.
Ensure the implement has appropriate baffling to reduce liquid surge.
Recheck the load capacity of your tractor using your manufacturer’s manual to ensure that you are not overloaded.
Review your manufacturer manuals or speak with your tractor/ implement retailer to see if baffles are available for your implement and what safety measures you should take with unbaffled loads.
Ensure proper and secure hitching
Proper and secure hitching is a must-have to optimise performance, and efficiency and for tractor safety. Improper hitching is a leading cause of tractors backflipping that can result in serious injury, or death.
We know a tractor is designed to pull heavy loads without tipping over backward, but doing those jobs safely within the design limits depends on using the correct hitching method.
- Hitching when recovering bogged machinery
Tractors can back-flip, for example, when a rope or chain is used to tow another vehicle out of a bog, and is connected to the top link of the 3-point linkage. View the safety tips for Managing the risks of bogged farm machinery.
Never connect a strap to the top link of the 3-point linkage when using a tractor to recover machinery from a bog.
Figure 5: The recovery of a tractor and implement from a bog.
Two images in Figure 5 show risks and suggested controls when recovering a tractor and implement from a bog.
The first image shows the uncontrolled risks including the bogged plant (1A) being heavier than the recovery tractor (1B) with the recovery strap connected to the top link (C) of the recover tractor.
The second image shows controlling the risks, including:
- (2A) reducing the weight of bogged tractor by disconnecting the implement
- (2B) using a recovery tractor that is larger and heavier than the bogged tractor
- (2C) connecting the recovery strap to the recovery tractor below the rear axle, typically the drawbar
- (2D) using a damper such as a weighted blanket or tire on the recovery strap to reduce any whipping in the event the strap or attachment points fail
- (2E) adding weights to the front of the recovery tractor to improve traction and reduce the front wheels from lifting off the ground.
Review your manufacturer manuals or speak with your tractor/ implement/ Recovery strap retailer to ensure that these recovery principles are correct for your tractor and implement.
- Single-point hitching
For trailers, wagons, and other implements that attach at a single point, the manufacturer approved hitches are the only safe hitching option. This could include for example a:
- draw bar
- ladder hitch
- K80 ball hitch
- piton hitch.
The single-point hitch is positioned low and designed to minimise the risk of a backflip.
Don’t attach any single-point load higher than the rear axle – this is extremely dangerous and can cause the tractor to flip over backward in an instant.
Where your single-point hitch requires a pin, ensure it is matched to the hitch design including the diameter and the load rating. Using a home-made pin or random bolt is likely to bend and fail. Also, make sure the pin is correctly secured with a lynch pin or an equivalent device.
Figure 6: The rear of a tractor with the single point hitch positioned low below the centreline of the rear axle.
Figure 6 shows a tractor with a K-80 ball hitch installed. The inset images show a variety of alternative hitches that may be available to be installed to the rear of a tractor. These include:
- ladder hitch
- piton hitch
- conventional clevis drawbar
- automatic clevis hitch.
Please review your manufacturer manuals or speak with your tractor / implement retailer to ensure this type of hitch is appropriate for your tractor and implement.
- 3-point linkage
This method uses 3 points of attachment to rigidly connect an implement to the front or rear of the tractor, fixing its orientation relative to the machine.
Your tractor may have a category 1 or 2 linkage - ensure the size and category of the implement matches the tractor linkage. Refer to your tractor and implement manual.
When you use the 3-point linkage, ensure all pins and securing devices are in good condition and correctly fastened.
The 3-point linkage transfers the weight and resistance of the implement to the tractor's drive wheels, improving traction. The additional weight at the front or rear can reduce longitudinal stability. Never use the top link or any other part of the 3-point linkage for single-point towing, as this creates a tipping hazard.
Some implement manufacturers may use the 2 lower links to connect trailed implement that have steering functions. For example, some large rotary rakes.
Refer to your operator’s manual to ensure implements are attached correctly.
Figure 7: 3-point hitch installed to the rear of a tractor with 2 lower links (1) and (2) and an upper link (3).
Review your manufacturer manuals or speak with your tractor/ implement retailer to ensure that you are safely hitching via a 3-point linkage.
Setting your tyres for stability
The tread design, lug shape, condition, and correct inflation pressure all play a role in avoiding wheel slippage, optimising tractor efficiency, and stability, especially on uneven or soft terrain.
Tractor tyres help keep a tractor stable by providing essential traction, distributing the load, and offering a wide, stable footprint that resists slipping and tipping during manoeuvres. Speak with your tyre supplier to ensure you have the right tyre for the task.
Correct tyre pressure
Correct tyre pressure is crucial for efficiency and stability. Changing the tyre pressure changes the shape and strength of the tyres. Check the tyre manufacturers recommendations for operating pressures.
- Underinflated
When the pressure is reduced, the area of contact with the ground increases, this helps with traction and reduces compaction. However, it reduces the tyres’ load carrying capacity and side wall strength which can cause instability and the tractor to tip sideways.
- Overinflated
When the pressure is increased, the tyre becomes stronger and can carry more load. However, the area of contact with the ground is reduced, which increases the likelihood of wheel spin, compaction of soil and tyre wear.
Traction and control
Tyre designs include:
- traditional lug tyres — these are designed to provide traction in pulling implements. The lugs on the tyres’ tread give grip and support stability, especially during turns and when pulling heavy loads
- industrial tyres — more commonly used on concrete yards, or flat gravel and have a higher weight capacity
- turf tyres — low impact, and reduces damage to grasses etc, but reduces traction particularly on slopes
To ensure maximum stability and grip, choose tractor tires that are specifically suited to your intended terrain and environment. Uneven wear may affect the operation of your tractor.
Review your manufacturer manuals or speak with your tractor/tyre retailer to ensure that you are using the best tyre for the job and better understand why you may be getting uneven wear on tyres.
Combined with correct ballasting, tyres in good condition can ensure the operator has safer control of the tractor when steering and braking.
Many tractors have an adjustable track width. Increasing the track width can increase the stability of the tractor. Consult your tractor manual or speak to your tractor retailer to learn how to optimise your tractor set up.
Impact of terrain on stability
Uneven terrain can reduce the stability platform and increases the risk of overturning.
Uneven terrain may include:
- slopes (hills, sides of dams)
- sink holes
- rabbit warrens.
The 2 main types of tractor overturns are:
- side overturns
- rear overturns.
Preventing Tractor Overturn Incidents - Safety, Health and Wellness in Agriculture provides information on how to operate your tractor to reduce your risks of overturning.
Your lines of defence if the tractor tips
Roll-Over Protective Structure
A Roll-Over Protective Structure (ROPS) works by creating a protective zone around the operator, preventing them from being crushed or pinned under an overturning tractor.
ROPS used together with a correctly worn seatbelt, provides the operator the most effective protection against injury during a rollover.
ROPS creates a protective zone
ROPS have a strong, rigid frame that holds up the weight of the tractor during a rollover. The ROPS shields the operator in a survivable space from being crushed by the tractor.
When ROPS are folded down the protective zone is no longer available to protect the operator.
Belt up and survive
The ROPS helps to keep you safe, but only if you wear the seatbelt. The seatbelt and ROPS work together as a system to prevent death and serious injury in a rollover.
If you are not wearing a seatbelt during a rollover, you could be partially or completely thrown from the cabin. This puts you at high risk of being crushed by the tractor or the ROPS itself.
Even within the cabin, not wearing a seatbelt during a rollover can cause you to be tossed around violently, hitting the walls, windows, controls, or protective frames. This can cause severe injuries or death.
Figure 9 shows a tractor towing a partially filled wagon down a well-maintained gravel road. The tractor and trailer jack-knifed causing the tractor to roll over partially, bending the ROPS structure while the wagon continued to roll along the road until it stopped. The operator was not wearing their seatbelt at the time of the incident and was ejected through the door opening as the glass shattered during the roll-over. Had the operator been wearing their seatbelt, they would have remained inside the protective area of the ROPS.
Please review your manufacturer manuals or speak with your tractor/ implement retailer to ensure that you understand how the ROPS and seatbelt work on your tractor.
Geo-fence restricted access
Tractors can be fitted with geo-fencing technology which allows the owner to set restrictions on unsafe terrain and prevent the tractor from operating in those areas. View a short video on geo-fencing set-up.
A clean cabin with secured gear
When you keep your tractor cabin neat and tidy, it’s not just about looking good. If the tractor becomes unstable and tips, any loose gear flying about can be a real hazard.
Loose gear in the tractor cabin, like tools or drink bottles, can be thrown around with great force if the tractor rolls over. They can behave like a projectile, flying through the air causing serious injuries to the operator.
A tidy cabin stops things from flying around and a seatbelt helps you stay secured in your seat, right where that ROPS can do its job. That's the best way to keep yourself safe if the tractor takes a tumble.