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The allowable axle weights listed on these pages and shown in the diagrams apply to all state trunk line highways. For information on state trunk line highways that are restricted to reduced weights during spring time, a current year's truck operator's map is necessary. Maps are available from Michigan Department of Transportation.
Permitted axle weights on state routes are determined by two factors; tire width and axle spacing or configuration.
The maximum wheel load for any axle operating single tires shall not exceed 700 pounds per inch of tire width.
Example: A single 10:00 tire equals 10" of tire width. 10" of tire width times 700 lbs. per inch would equal 7,000 lbs. or a total of 14,000 lbs. for the axle.
The following diagrams are shown with steering axle tires rated at 10:00 for
a weight of 14,000 lbs.
A single axle which is separated from all other axles by a spacing of 9 feet or more, center to center, is allowed a maximum weight of 18,000 lbs.
An axle which is separated from other axles by a spacing of less than 9 feet, but more than 3 feet 6 inches, is allowed a maximum weight of 9,000 lbs.
On a legal combination of vehicles, only 1 tandem axle assembly shall be permitted at the gross weight of 16,000 lbs. per axle and no other tandem axle assembly in the combination shall exceed a gross weight of 13,000 lbs. per axle. Operators may elect to carry 16,000 lbs. per axle on the tandem of their choice. When five axle tandem tandem units do not exceed 73,280 lbs. gross weight, then each tandem axle assembly shall be permitted on the state trunk line highways at a gross weight of 16,000 lbs. per axle, providing there is an axle spacing of 9 feet on both sides of the tandem assembly.
During the time spring weight restrictions are in effect on frost restricted routes, axle loadings are reduced 35%. The speed limit on restricted roads is 35 mph.
Single Axle Dual Tires
11,700 lbs. per axle; 9' or over between axles.
Tandem Axle - Less than
Nine Feet between Axles
20,800 lbs. both axles, 10,400 lbs. each.
Multiple Axles Over 3
and 1/2' but Less Than 9'
8,450 lbs. per axle; Tri-axle 25,350 lbs. per assembly.
Single Axle, Single Tires
Wheel size (doubled because of two tires) time 450 lbs. per inch of tire width; 35% reduction from legal load.
The following roads are not posted for seasonal weight restrictions and normal loading will be permitted, plus the following axle weights will be in effect during the time the weight laws are being enforced. Shiawassee County Weighmasters will be enforcing the law.