Creative Solutions

In recent years, truckers running end dump semi trailers have gotten more payload by using a tridem under the trailer. This takes advantage of a quirk in the Formula B table which allows 42,500 pounds to be carried on three axles with a bridge of 9 feet.

Truckers load the tridem to perhaps 40,000 pounds. The tractor tandem can then carry 32,000 and the steering axle gets 8,000. Federal and state authorities bought the idea, and dump truckers got their 80,000 pounds – though at the expense and extra tare weight of a sixth axle. (see Clement Industries comments below)

Within the last two years, a dump trailer builder came up with a simpler idea: the reverse-sliding tandem. Move the trailer’s tandem rearward when the rig’s on the road to satisfy the inner and outer bridge dimensions, then slide it forward, ahead of the tailgate, when the load has to be dumped.

This is an example of creative designing of equipment specs to carry more payload and still obey the bridge law.

from: HEAVY DUTY TRUCKING, March ’86

Clement comments regarding tridem dump trailer:

72,000 pounds on the inner bridge (40,000 + 32,000) requires 38 foot inner bridge. It would take a minimum of a 40 foot long trailer with a zero inch 5th wheel setting to get to 38 feet inner bridge. Plus the 3rd axle adds 2,000 pounds of additional weight.

By comparison a 38 foot tandem axle trailer would get 2,000 pounds more payload by taking advantage of the “ATA bump” of 68,000 pounds on the inner bridge at 36 feet, and shifting the 5th wheel and payload ahead approx. 20 inches to get weight transfer to the steering axle.

Both examples achieve 80,000 gross but the 3 axle trailer will be 2 feet longer (40 feet), 2,000 pounds heavier and require the extra expense of a 3rd axle.

A more practical solution is the Clement 32 foot Bridger end dump trailer, that will legally axle out 80,000 pounds gross weight with water level loads. Click on “The Bridger” sliding tandem link below or request a brochure on the Bridger from your local Clement Dealer.