M870 Series Low Bed Semitrailer

The M870 Series Low Bed Semitrailer family consists of a series of models, variants of the original M870 which was type classified in 1976, based on the CMI/Load King 403LF commercial trailer. While the models vary in load capacity and minor improvements in operating features, the basic mission remains to transport construction equipment, tracked and wheeled vehicles as well as general cargo in containers or bulk. M870 semitrailers are usually assigned to Engineer units to haul their heavy equipment, not Transportation.

The M870 semitrailer has evolved with its prime mover tractors, progressing from use of the M818 5-ton tractor, M920 Truck, Tractor MET, and the M931 5-ton tractor, to the M916 LET, the MK16/16A1 LVS Tractor, and LVSR MKR16 tractor, or AMK / MK31 MTVR 7-ton Tractor.

Model change improvements included moving the spare tire to the gooseneck then back to the rear, adding attached ramps to the rear for loading and unloading, having an interchangeable king pin of 3.5 inches or 2 inches for different prime movers, and others.

M870 Series Low Bed Semitrailers operate on highways and improved roads (graded gravel). It is not designed for off-road or cross country operation.

A D-7 Caterpillar Bulldozer backs onto an M870A1 Semitrailer, Low Bed, 40-ton, at Bjugn Cave, Orland Main Air Station, Norway, July 1997
A D-7 Caterpillar Bulldozer backs onto an M870A1 Semitrailer, Low Bed, 40-ton, at Bjugn Cave, Orland Main Air Station, Norway, July 1997.

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M870 Semitrailer, Low Bed, 40-ton, Construction Equipment Transporter

M870 Semitrailer, Low Bed, 40-ton, Construction Equipment Transporter.  Reference drawing from TM 43-001-31 June 1985
M870 Semitrailer, Low Bed, 40-ton, Construction Equipment Transporter. Reference drawing from TM 43-001-31 June 1985.

The initial version of the M870 Semitrailer, Low Bed, 40-ton, Construction Equipment Transporter is a 6-wheel, tandem axle, dual-tire semitrailer with a heavy-duty steel frame and a flat wooden cargo bed. With its prime mover, the M870 is used to haul construction equipment and material on improved and semi-improved roads. The M870 can be used for cross-country operation over open, selected terrain. The M870 is equipped with air brakes; the prime mover supplies brake air pressure and control.

The M870 has a two position gooseneck and portable loading ramps that allows it to be loaded and unloaded from either the front or the rear. The two position gooseneck also permits the M870 equipment transporter to be towed by 5 ton or 10 ton tractors. A tool well is also located in the gooseneck.

The M870 has six lashing rings (D-rings) on each side. It also has two D-rings on the rear cargo bed and four D-rings on the gooseneck. Outrigger planks can be moved from the center of the cargo bed and fitted outboard to widen the bed. The wheel wells are open but can be covered by steel plates fabricated by using units.

Deficiencies of the M870 Semitrailer

The M870 semitrailer was criticized for these deficiencies:

  • No storage provided for the spare wheel and tire
  • Inadequate storage space for included items of equipment
  • Not strong enough for hauling equipment assets over long distances, especially when hauling off-road -- the tires and rims routinely go flat and bend
  • Too small for larger pieces of engineer equipment such as scrapers, twenty-five ton cranes, and D9 bulldozers
  • Cannot transport secondary loads because the tiedown provisions are only adequate for the empty M870 semi-trailer

USMC Combat Logistics Battalion 8 uses an M870-series trailer (M870A2??) to deliver bulldozer to Forward Operating Base Geronimo, Nawa district, Helmand province, Afghanistan, 11 Sep 2009
USMC Combat Logistics Battalion 8 uses an M870-series trailer (M870A2??) to deliver bulldozer to Forward Operating Base Geronimo, Nawa district, Helmand province, Afghanistan, 11 Sep 2009.

While the M870 semitrailer has been extremely useful in its planned roles, and field adaptations took care of some issues, improvements were designed that resulted in variant models. Additional information and photos of these variants are on the linked Olive-Drab.com pages:

In November 2009, TACOM issued a purchase description document for a new 40-ton variant of the M870, the TRAILER, MEDIUM HEAVY EQUIPMENT TRANSPORTER (MHET), M870A4.

M870 Semitrailer Characteristics

Length 41 ft 11 in (12.8m)
Width 8 ft 0 in (2.4m)
Height 5 ft 4 in (1.6m)
Ground clearance (40-ton load) 1 ft 1.5 in (0.335m)
Curb weight 8.25 tons (7484kg)
Max payload; 40 tons (36,287kg)
Gross weight 48.25 tons (43,771kg)
Tires 13 tires 10:00x15 14-ply, commercial highway tread
Brakes S-cam, two-shoe, double anchor, interval expanding, air actuated
Suspension Triaxle mechanical
Max speed empty 55 mph (89kmh)
Max speed 40-ton load 40 mph (64kmh)

Table data from TM 5-2330-378-14&P

The full nomenclature for this trailer is Semitrailer, Lowbed: 40-ton Construction Equipment Transporter M870 (CCE). The M870 was assigned NSN 2330-00-133-1731.

The Operator's, maintenance and parts manuals for the M870 include:

  • TM 5-2330-360-14&P (M870 only)
  • TM 5-2330-378-14&P (M870/M870A1)

The M870 was manufactured by CMI/Load King as their model 403LF commercial 40-ton trailer.

U.S Army Engineers from Charlie Company, 84th Engineer Battalion attached to 25th Infantry Division unloading their heavy equipment from M870-series trailers in preparation to conduct Al Fatah float bridge embankment repair, in northeast Bayji, Iraq, 28 March 2009
U.S Army Engineers from Charlie Company, 84th Engineer Battalion attached to 25th Infantry Division unloading their heavy equipment from M870-series trailers in preparation to conduct Al Fatah float bridge embankment repair, in northeast Bayji, Iraq, 28 March 2009.

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