KrAZ-255

KrAZ-255 at a glance

The KrAZ-255 was designed to carry heavy loads and tow heavy trailers where there were no proper roads. It was supplied to the armed forces of many countries as well as to civilian operators, and logging versions worked in forestry for decades. The plant's story is told in the history of KrAZ, and related trucks, including the KrAZ-256 dump truck and the KrAZ-250, are in the KrAZ catalogue.

From KrAZ-214 to KrAZ-255

The KrAZ-214, built from 1956 to 1967, had established the layout of a heavy bonneted 6×6 truck but its YaAZ-206B diesel was too weak for the growing loads. For the KrAZ-255, engineers kept the proven cab, platform and suspension and installed the much more powerful YaMZ-238 V8 four-stroke diesel with a new YaMZ-236N five-speed gearbox in place of the YaAZ-204. The most visible change was the use of very wide tyres, measuring 1,300 × 530 × 533 mm, which reduced ground pressure and made the truck far more capable on soft ground. Their size earned the truck a nickname from drivers that compared the wide tyres to bast shoes.

Design and cab

The KrAZ-255 does not try to impress with styling. Its cab, carried over from the KrAZ-214, has a wooden frame covered with steel panels and sits behind the long bonnet. From 1969 the lights were revised, with side and indicator lamps moved, and the original drop-shaped indicators were replaced. The standard body is a cargo platform with a lattice tailgate, folding bench seats along the sides, hoops and a canvas cover. Controls were laid out for easy use: pneumatic power steering was later replaced by hydraulic power steering, and levers operate the gearbox, transfer case and axle differential lock.

Engine and transmission

The YaMZ-238 has a cast-iron block and a mechanically driven high-pressure fuel pump with a separate pumping element for each cylinder. The transfer case is controlled by three levers, and five propeller shafts connect the gearbox, transfer case and three axles, with an intermediate support on the long rear shaft. The axles have double reduction final drives, and the front axle uses constant-velocity joints so that torque reaches the front wheels even when they are turned.

The YaMZ-238 engine family

The YaMZ-238 belongs to a modular family of V-engines developed in the 1950s, in which the six-cylinder YaMZ-236 and the eight-cylinder YaMZ-238 share many parts. Both are four-stroke, liquid-cooled diesels with overhead valves and a cast-iron block. In the KrAZ-255 the V8 was naturally aspirated; later versions of the engine for other trucks received turbochargers and higher outputs. The same engine family powered many heavy trucks of the period, including versions of the MAZ-500 and the Ural-5557, which made spare parts and servicing knowledge widely available.

Chassis and brakes

The front axle hangs on two semi-elliptic leaf springs with double-acting hydraulic dampers, and the rear tandem rests on a pair of semi-elliptic springs with three pairs of reaction rods. Brakes are drums on all wheels with a dual-circuit air system: one circuit for the front and middle axles and one for the rear axle. A mechanical drum transmission brake serves as the parking brake, and an engine retarder with air-operated control helps on long descents. The air system includes a moisture separator and anti-freeze protection. The stopping distance from 40 km/h is about 17 metres, or 18.5 metres with a trailer.

Fuel, range and fluids

The KrAZ-255 carries two 165-litre fuel tanks, enough for a range of about 750 km. Fuel consumption is about 30–40 L/100 km depending on load and terrain. The truck can ford water up to about one metre deep. Its service fluids reflect its size: the cooling system holds 51 litres of coolant, the engine 32 litres of oil, the transfer case 16 litres, the power steering 3.9 litres, the steering box 1.25 litres, each of the three axles 12 litres of gear oil and each shock absorber 0.75 litres.

Dimensions and weight

The turning circle exceeds 14 metres.

KrAZ-255 versions

Other special bodies included bridge-laying and pontoon equipment and radar platforms, and a KrAZ-255D prototype was built for use with a powered semi-trailer. From the 1970s the headlights and indicators were placed in rectangular metal housings. Auxiliary equipment on many trucks included an engine pre-heater, a winch on the 255B and 255L and tyre-pressure regulation on the 255B versions.

KrAZ-255 versus KrAZ-260

The KrAZ-260 of 1979 was developed as the modernised successor. It kept the 6×6 layout and the heavy-duty concept but introduced a new, more spacious cab and an updated interior, and it was built alongside the KrAZ-255 until 1994. For many operators the two trucks did the same jobs. In 1994 both were replaced by the KrAZ-6322.

Successor and legacy

The KrAZ-255 replaced the KrAZ-214 in 1967 and stayed in production for 27 years, a remarkably long life for a heavy truck design. The KrAZ-260 of 1979 introduced a new cab and interior and was built alongside the 255 until 1994, when both gave way to the KrAZ-6322. The KrAZ-255 served in the armed forces of more than twenty countries and in civilian roles, such as with Bucharest's public transport company, which used four as recovery vehicles from 1978. Some operators, such as Kazakhstan, announced plans to replace them only in 2016, showing how long these trucks remained in service. Owners value the KrAZ-255 for its reliability, easy repair and the wide availability of spare parts, and many trucks are still at work today. Comparable heavy trucks include the MAZ-500 and the all-wheel-drive KamAZ-4310.