Determining Weight of an IoH or Ag CMV

Diagram of measurments for a farm tractor and a manure tanker including axle spacing andd weights.To determine the maximum GVW of your IoH or Ag CMV when maximum axle weight apply requires several measurements.

A. Total distance from the center front axle to the center of the rearmost axle of the vehicle or vehicle combination. In the example the total distance is 39 feet 6 inches and you can round up; to 40 feet.  Measuring is defined in s. 348.15(5m) Wis. Stats.

Use this distance with Column A of the IoH/Ag CMV Maximum Weight Table

B. Next step is to measure between the individual axles. Axles need to be at least 42 inches apart to count as separate axles. This helps you determine the number of axles that will apply on the IoH/Ag CMV Maximum Weight table. The example IoH vehicle combination has 5 axles.

The maximum gross weight for example vehicle is 84,000 pounds as determined using weight table.

The maximum gross weight for example vehicle is 84,000 pounds as determined using weight table.

Back to the IoH/Ag CMV Maximum Weight Table with the number of axles. For this example, Column E (5 axles) will be used. Follow Column A across and where it intersects with Column E that is the maximum gross vehicle weight for this combination.The maximum gross vehicle weight for this farm tractor and tanker is 84,000 pounds. To exceed this weight, you will need to obtain a No Fee Permit or haul a lighter load.

C. Now that the maximum gross vehicle weight has been determine, it is time to review the individual axle weights. Each axle must carry at least 8 percent of the gross vehicle weight. to qualify as an individual axle per s. 348.15(8) Wis. Stats. Maximum axle weight is 23,000 pounds. If you have an axle that exceeds 23,000 pounds, you’ll need to obtain a No Fee Permit to operate on highways were the maximum axle weight apply.  To review roads that require maximum axle weights see Local Options.

In the example, the manure tanker has unladen weights. For some vehicles you’ll need to consider loaded weight of the vehicle. One factor to consider is that towed implements may add weight to the rear of the towing power unit.

D. Measuring  axle gauge

A diagram showing how to measure for axle gauge.

Diagram showing how to measure for axle gauge on an IoH power unit with triple tires on rear axle.

A color photo of a farm tractor with triple tires on rear axles.

To measure the axle gauge on this farm tractor, measure from center of middle tire on left side to center of middle tire on right side.

Bridges are designed for the standard width of commercial motor vehicles of 8 feet 6 inches. Agricultural vehicles, primarily IoH, are wider than the standard commercial motor vehicles. In reviewing permit applications with routes including bridges, axle gauge is a needed measurement. It is used by bridge engineers to assess where the vehicle will travel on the bridge and the impact of the vehicle on the bridge supports.

Axle gauge is measured from the center of the axle or axle group to center of the axle or axle group.

Effective March 3, 2016, farm machinery dealers in Wisconsin must now provide unladen gross vehicle weight and axle weight in writing. This is not required for private sales or auction sales.

Taking the time to measure and weigh your implements of husbandry and agricultural commercial motor vehicles is an important first step to determine which vehicles may need a No Fee Permit to operate legally on Wisconsin highways.

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