Ballasting and optimizing tractor performance overview
8R with front support and weights

8R with front support and weights

Achieving peak performance from the 8R Series Tractor requires careful planning at the time the tractor is purchased.  Key options like tire size selection and cast weight packages, along with properly adjusted tire inflation pressures, have a significant impact on overall tractor performance.
Basic ballasting definitions
 
Ballast is mass added to the tractor chassis and/or wheels to:
  • Increase total weight
  • Influence the weight distribution between the front and rear axle (called the fore-aft static balance of the tractor, and static means the front and rear axle loads are determined when the tractor is parked)
The static weight distribution between the front and rear axles is sometimes called the weight split.  It is usually expressed as the percentages of total tractor static weight supported by the front and the rear axle.  For example, if the front axle supports 40 percent of the total static tractor weight, the tractor has a (40/60) weight split. The percentage on the front axle is always stated first in this form.
Ballast types
 
8R Series Tractor front weight support

8R Series Tractor front weight support

8R Series Tractor with front suitcase weights

8R Series Tractor with front suitcase weights

8R Series Tractor with outer rear cast weights

8R Series Tractor with outer rear cast weights

8R Series Tractor with inner rear cast weights

8R Series Tractor with inner rear cast weights

Preferred ballast for 8R Series Tractors are cast iron rear wheel weights and front suitcase weights. When applying inner or outer rear cast weights, the amount of axle load equals the amount of ballast added since it is added directly to the rear axle. However, front weights apply more weight to the front axle and remove weight off of the rear axle as a result of the lever effect. For more details, see the section on: adding front weights and transfer effects.
 
In some cases, it may be necessary or desirable to remove either front or rear ballast. Installation and removal of rear weights on the outside of the wheels requires the use of a crane or forklift. If possible, configure ballast so that removal of inner rear wheel weights is not required after initial installation at the factory or dealership (rear inner cast weights require the tire to be removed).
 
Another type of ballasting is achieved by adding fluid to the tires. Ballasting with fluid should be avoided if possible. Liquid ballast causes a stiffening effect to the tire sidewall that gives the operator a rough ride and makes the tractor more susceptible to power hop. If liquid is used in the rear tires, all tires on the axle must be filled to the same level which should not exceed 40 percent fill (4 o'clock valve stem position). Specific information on the use of liquid ballast is given in: using liquid ballast in tires section.
Factors in determining amount of ballast
 
  • Soil surface – loose or firm
  • Terrain – flat or slope
  • Type of implement – integral/semi-integral or towed
  • Travel speed – slow or fast
  • Tractor power output – partial or full load
  • Tractor weight
  • Kg/PTO-hp (lb/PTO-hp) required
  • Tires size – small or large
  • Type of front axle - MFWD or Independent-Link Suspension (ILS™)
Effects of too little ballast:
  • Excessive wheel spin or slip
  • Loss of power transfer
  • Tire wear
  • Fuel waste
  • Lower productivity
Effects of too much ballast:
  • Soil compaction
  • Power loss
  • Increased load
  • Fuel waste
  • Lower productivity
Benefits of proper ballast:
  • A tractor properly ballasted for a given type of application or implement (light, medium and heavy) has both the correct total weight and the correct static balance (weight split) for that type of implement.
  • Pulling a lighter load at a higher speed is more economical and more efficient than pulling heavier loads at a lower speed.
  • When changing from one implement or attachment to another it may be necessary to reconfigure ballast on the tractor.
  • Correct ballast allows most efficient use of available power but will not compensate for an oversized implement for the tractor. Adding ballast will not improve performance, if engine speed falls below rated speed and/or wheel slip is not beyond the recommended range.
  • When choosing tires, select wide, tall, radial tires to provide the best tractive performance, and smoothest ride to effectively control power hop.
 
The amount of ballast required and the locations of ballast weights depend greatly on the type of implement being used.
Ballasting is usually required to:
 
  1. Ensure the front axle carries sufficient weight for steering security and stability with field draft loads as well as for road transport.
  2. Provide sufficient traction to efficiently pull high-draft loads.
  3. Provide the proper fore-aft balance to minimize the occurrence of power hop in mechanical front-wheel-drive (MFWD) tractors.
  4. Ensure the rear axle carries sufficient weight for traction, braking, and stability when a loader or other front implement is attached to the front of the tractor.
Ballast limitations
 
Ballast should be limited by the lowest of either tire capacity or tractor capacity. The carrying capacity of each tire should not be exceeded.  If a greater amount of weight is needed, larger tires must be considered. Refer to the load capacity chart in the operator’s manual for optimum tire selection.
 
NOTE: Tractor weight exceeding heavy ballast limits should be avoided and is considered an overload condition.
 
Last Updated : 25-Jul-2013