Gross axle weight rating
The gross axle weight rating (GAWR) is the maximum distributed weight that may be supported by an axle of a road vehicle. Typically, GAWR is followed by either the letters FR or RR, which indicate front or rear axles respectively.
Road damage rises steeply with axle weight, and is estimated "as a rule of thumb... for reasonably strong pavement surfaces" to be proportional to the fourth power of the axle weight. This means that doubling the axle weight will increase road damage (2x2x2x2)=16 times. For this reason trucks with a high axle weight are heavily taxed in most countries.
Examples of GAWR on common axles.
|Dana 30||2,770 lbs||Dana Corp.|
|Dana 35||2,770 lbs||Dana Corp.|
|Dana 44||3,500 lbs||Dana Corp.|
|Dana 50||5,000 lbs||Dana Corp.|
|Dana 60||6,500 lbs||Dana Corp.|
|Dana 70||10,000 lbs||Dana Corp.|
|Dana 80||11,000 lbs||Dana Corp.|
|Dana S 110||14,706 lbs||Dana Corp.|
|Ford 9-inch axle||3,600 lbs||Ford Motor Company|
|Ford 8.8 axle||3,800 lbs||Visteon|
|Sterling 10.5 axle||9,750 lbs||Visteon|
|10.5" Corporate 14 Bolt Differential||8,600 lbs||American Axle|
|11.5 AAM||10,000 lbs||American Axle|
|10.5 AAM||9,000 lbs||American Axle|
|Saginaw 9.5-inch axle||6,000 lbs||American Axle|
Maximum weight laws
In the EU and U.S. legal maximum load restrictions are placed on weight, independent of manufacturer’s rating. In the EU a tractor can generally have 10 tonnes on a single axle, with suspension type and number of tires often allowing slightly higher loads. In the U.S. weight restrictions are generally 20,000# on a single axle, and 34,000# (less than two single axles) on a tandem. The primary factor is distance between axle centerlines, also used to measure bridge formulas. A bridge formula does not reduce axle load allowances, rather Gross Vehicle Weights(GVW), which can affect load distribution and actual axle weights. 
- "Equivalent Single Axle Load". Pavement Interactive. Retrieved 25 April 2012.
- "Truck Weights and Highways". South Dokota Department of Transport. Retrieved 25 April 2012.
- "Guidelines on Maximum Weights…Criteria (EU)". Road Safety Authority. 2013. Retrieved 25June2013.
- "Freight Management and Operations: Bridge Formula Weights". U.S. Department of Transportation. Retrieved 25June2013.
- "Freight Management and Operations: Size Regulations". U.S. Department of Transportation. Retrieved 25Jun2013.
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