Max Legal Weight for GVW under 80,000 lbs and Max Permitted Weight for GVW over 80,000 lbs
Maximum load limits may depend on the following:
Depending on the conditions listed, your vehicle may be subject to the maximums found under the bridge formula or the normal loading standards.
The bridge formula applies to vehicles operating on interstate highways and specially designated highways which:
Spacing Between Axles
Normal Exceeding when Seasonal Load Limitations are Not in Force
Seasonal Load Limitations (Speed Limit 35 mph)
Vehicles Exceeding 80,000 lbs. Gross Weight
Vehicles 80,000 lbs. (Or under) Bridge Formula Gross Weight
Rigid (25% Reduction)
Flexible (35% Reduction)
9' or over *normal loading
3 1/2' or more but less than 9' *normal loading
When part of a tandem axle assembly *on designated routes only
34,000 pounds on tandem
When less than 3 1/2' *normal loading
Maximum load on any wheel shall not exceed (pounds per inch of tire width)
*On any 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 such combination of vehicles should exceed a gross weight of 13,000 lbs. per axle. On a combination of truck tractor and semi-trailer not having more than 5 axles, load, 2 tandem axle assemblies shall be permitted at a gross weight of 16,000 lbs. per axle, if there is no other axle within 9' feet of any axle of the assembly.
The Bridge Gross Weight Formula was developed to prevent stress to highway bridges caused by heavy trucks. The formula provides a standard to control the spacing of truck axles and weight on those axles. Vehicles with a gross weight of 80,000 pounds or less may be eligible for increased weights using the Bridge Gross Weight Formula. Vehicles exceeding a gross weight of 80,000 pounds or the gross weight calculated using the Bridge Weight Formula are not eligible for bridge weights.
20,000 pounds for a single axle;
34,000 pounds for a tandem axle group.
W = The maximum weight in pounds that can be carried on a group of two or more axles to the nearest 500 pounds;
L = The spacing in feet between the outer axles of any two or more consecutive axles;
N = The number of axles being considered.
The bridge formula allows up to 20,000 lbs. per single axle, if the vehicle is equipped with large enough tires. Steering axle weights will vary depending on the gross weight of the vehicle.
In Michigan, it is not permitted more than 700 pounds per inch of tire width for a single axle.
Source of information: http://www.truckingsafety.org/Portals/0/GuideBooks/18th%20Ed%20TDGB.pdf