Tractor ballasting plays an important role in getting those chores and tasks done in the fastest and most economical manner. One aspect is controlling rear wheel slip. Too little weight and the tires spin, resulting in excessive tire wear and poor productivity. Too much weight and not only is fuel wasted but adverse ground compaction occurs. Studies from respected institutions such as Iowa State University Extension and Alberta Agricultural & Rural Department Ministry suggest the optimum amount of slippage is 10 – 15% for 2WD tractors and 8 – 12% for 4WD machines. Keeping slippage to these levels allows transfer of the most power possible to the drawbar.
A second important aspect is the protection of components such as the front axle. Front axles are generally smaller than their brothers at the rear and are not as heavy duty. When implements such as a front end loader (FEL) are added, front axle stresses are increased and without proper counterbalancing, can lead to premature failure of the axle and related components. As always, the first rule is to read the owner’s manual to learn the recommended amount of ballasting needed.
In this feature we will explore the different methods of adding ballast and the pros and cons of each, how to measure slippage, and the importance tire pressure plays.
A ballast box can be as simple as a poured concrete cylinder or block with category-sized hitch pins extending outward from the mass, or steel fabricated shells filled with rocks, lead, steel, barbells, etc. In most cases this weight will be carried by the tractor’s three-point hitch (3PH).
Pros: Ballast boxes can add a lot of weight in a small area and be removed or added whenever needed and only then. Prices range from the cost of concrete and a steel bar to $250 plus for a purchased box and then whatever materials are added for weight. Clever builders might cast in PVC tubes for transporting rakes and/or other tools. This method of adding weight is not affected by temperature extremes.
Cons: These boxes add length to the tractor and lessen maneuverability. Weight is carried by the tractor frame, axles and tires, though as long as the ballast is sized according to manufacturer recommendations the extra heft should not be a problem.
Suitcase Weights and Implement Ballast
Another method of adding weight is through suitcase-style weights that can be hung on 3PH brackets. This method lets the user choose and vary the amount of desired weight. Common 3PH implements also make for good ballast. Box blades, tillers and rotary cutters often do double duty for this task. And in the case of box blades, most designs have vertical steel plates/beams that allow suitcase weights to be hung from those perch points. For ballasting of rear mounted or drawn implements, it’s not uncommon for tractors to have weight brackets built into the front frame assembly that can accept suitcase weights.
Pros: One big benefit is the low cost – free if an implement has already been purchased and is used as ballast. It is relatively easy to add or remove weight and ballast can be varied depending on the need or task. This ballast method is not affected by temperature extremes.
Cons: Weight added in front or behind the tractor also extends the overall length, which can hamper maneuverability. As with ballast box designs, added weight is distributed over the tractor frame, axles and tires.
Ballasting through this method can be accomplished through cast discs that fit inside the tractor wheels or plastic shells filled with concrete or sand. Some systems even employ a starter first weight that can accommodate additional layers. Larger tractors such as the Case Maxxum 115 we tested in October may even come with bar axles ready to accept additional ballast.
Pros: Ballast can be added or removed, though not as easily as a slip on suitcase weight. Weight is entirely carried by the tractor axle and tires (better than 3PH ballast). Not affected by temperature extremes.
Cons: Weight adding ability is limited to inner wheel space. If additional weight layers are added, maneuverability is affected. And in the case of bar axles which we liken to Ben-Hur hubs, when installed they call for an extra degree of caution around posts and doors. Wheel weights generally cost $1 – $2/lb. And if they are made from cast iron, wheel weights need to be painted and then maintained.
Adding fluid to tires has long been a preferred method of adding weight. This method doesn’t occupy the 3PH or increase turning radius/decrease maneuverability. Fluid-filled tires also have a less “springy” feel due to the displaced air content. This can especially be of benefit in precise loader work where implement fidgetiness can be counterproductive or even dangerous. And for all the below methods, the weight is no longer carried by the tractor frame, axles or tires since it is distributed across the footprint directly to the ground.
Starting with water, we’ll explore some of the different liquids used.
Pros: Water is about as affordable as you can get. As well, it’s non toxic, so it wont’ kill the lawn, garden or crops if spilled.
Cons: 32-degree F freeze point. Combines with tire air (oxygen) and will cause rims to rust over time. Nitrogen substituted for straight air can alleviate this but requires access to a filling station. At 8.3 lbs per gallon is one of the least efficient (lightest) methods of adding weight.
Pros: This dense chemical salt solution of calcium and chlorine has long been used in farming, ranching and commercial applications. It’s an effective method of adding weight (11.5 lbs per gallon), is inexpensive, and is freeze protected until -30-degrees F to -40-degrees F depending on mixture.
Cons: This method requires tubes, which cost $30 – $80 per tire. As well, it has a hygroscopic nature, meaning if exposed to air it will attract/absorb water and cause rust to metal surfaces. It requires specialized equipment to fill tires, along with operator safety precautions. It is highly corrosive and toxic. If ingested by a pet the results will most likely not be good. Calcium Chloride is classified by many states as a hazardous waste, requiring special handling and disposal methods. It will contaminate soil and prevent plants from growing if it spills.
Pros: This is relatively inexpensive, while protecting from freezing to about -25-degrees F depending on mix.
Cons: Automotive-style anti-freeze is highly toxic. If spilled, it will contaminate soil and pollute ground water. It is toxic to animals. Also at 8.3 lbs per gallon, Anti-Freeze/Glycol is no more efficient at adding weight than water.
Windshield Washer Solvent
Pros: Relatively inexpensive, this is usually non-corrosive and non-flammable.
Cons: Also adds only 8.3 lbs. per gallon. Considered somewhat toxic and is certainly not pet safe.
Cons: Extremely flammable. Highly toxic, even to rubber and will over time attack tires and rims. It also weighs less than water.
Pros: Inexpensive beet juice mixture costs approximately $0.28/lb. Weighs 10.7 – 11.0 lbs per gallon (about the same as calcium chloride). It is non-corrosive and non-toxic. If spilled it will not contaminate the soil or kill your pets. As well, it does not require tubes.
Cons: May attack rubber joints in valve stems (metal stems are recommended).
How to Measure Slippage
Slippage is easily measured by two people without specialized equipment. The first step is to stake out a course containing similar conditions to the field where the tractor will be used. A chalk mark (we like to put it at the valve stem position) helps keep track of the revolutions to be measured.
One person starts the tractor with the implement running or in ground-engaging position before reaching the start point. When the tractor reaches the starting line, the helper (at a safe distance) notes the position of the chalk line and begins to count revolutions. When 10 revolutions are reached, the helper places a marker. The tractor is then returned to starting line to begin the course again, this time without the implement engaged or lowered (using the same gear and engine RPM). From the starting line, the helper again counts revolutions (to the nearest ¼ turn). Then the following formula is applied:
Percent Slip = (10 revolutions with load) – (10 revolutions without load) X 100 then divided by (10 revolutions without load).
For example, if the distance it took to get 10 revolutions under load takes 8.5 revolutions without load, the calculated slip would be 15 percent.
The Importance of Tire Pressure
It is well known that underinflated tires wear sidewalls quickly. A natural tendency is to overinflate tires but that reduces lug contact with the soil which increases slippage and fuel consumption. Correct tire inflation for the load carried can be found on the tire manufacturer’s website or in the operator’s manual. Combined with proper ballasting and knowledge of axle weight, proper inflation values can be extrapolated.
To achieve maximum performance, ballasting and tire inflation must be considered. What type of ballast is right for your situation and conditions will be dictated by the implements at your disposal, whether your tractor is single-use or not (task dedicated), your budget, need and ease to add/remove weight and preferences that may be specific to your farm.
For a multi-use tractor, the ability to remove ballast in late spring for light drawbar work such as planting or spraying and for mowing and baling, and then the ability to add ballast for fall tillage will be the prime driver. For single-use machines those needs may be different. Whatever the type of ballast used, the prime driver always is maximum productivity with maximum fuel economy. Anything less and the farm suffers.