How to calculate Bridge Formula ?
1. Axles are measured to the nearest foot between the extremes on any group of two or more consecutive axles.
2. Gross weights for 5 and 6 axle vehicles apply to combinations only. For vehicles not in combination (straight trucks), only 4 axles shall be used in determining maximum gross weight.
3. Two consecutive sets of tandems may carry 34,000 pounds each providing the overall distance between the first and last axles of such consecutive sets of tandems is 36 feet or more.
4. If the distance between the centers of the first and third axles in a group of consecutive axles does not exceed 96 inches, the group is a tandem.
5. The maximum weight of any single axle is 20,000 pounds and the maximum weight of any tandem is 34,000.
6. To compensate for these weight restrictions, some tractors have a fifth wheel (also called as "slider"), that can slide forward ro backward on the tractor frame. This sliding motion shifts and balances the trailer's kingpin weight put on each axle without moving the cargo around. Sliders let you adjust the wheelbase in order to be in compliance with the bridge law.