At the Minsk Automobile Plant, this vehicle was jokingly called the "truck in reverse." The experimental MAZ-520V sharply departed from conventional logic: two steering axles were located at the front, while there was only one driven axle at the rear. Instead of a classic all-terrain tractor with a pair of rear axles, the result was a machine with an inverted layout — and that was precisely what made it unique.
The six-wheeled tractor was built in 1964. It existed in a single example, had a curb weight of about seven tons, and was designed to work with a semitrailer weighing up to 27 tons. Over the course of a year, engineers and test drivers operated the machine on the roads of Belarus: they recorded malfunctions, prepared reports, and eliminated defects. After that, the project was quietly closed without loud announcements.
The reason for the failure turned out to be far more complex than it might seem at first glance.
Why the front was overloaded and the rear was useless
The key problem lay in the layout. As with the production MAZ-500, the cab on the prototype tractor was positioned above the engine. As a result, significant weight — the engine, driver, passenger, and part of the load — fell on the front section. At the same time, the load was borne by a single axle with single wheels. The rear axle, by contrast, ended up underloaded: the empty tractor easily lost traction on climbs and lost stability on slippery surfaces.
Production Minsk trucks allowed an axle load of up to 10 tons. For main highways, this was considered acceptable, but on secondary roads such values effectively destroyed the pavement.
The situation was complicated by exports. In Finland, one of the active markets for Soviet equipment, legislation limited axle load to eight tons. This meant that MAZ trucks could operate there only underloaded, which made their use economically questionable.
It was after a business trip to Helsinki that MAZ chief designer Mikhail Vysotsky proposed a non-standard solution: add a second steering axle at the front. The load would then be distributed over three axles, roads would suffer less, and the permissible gross weight of the road train would increase. Similar vehicles were already being produced in Europe at that time — by Mercedes-Benz and FIAT.
On the drawings, the idea looked flawless.
How the MAZ-520V was designed
When developing the tractor, the engineers deliberately abandoned radical innovations. They took the production MAZ-500 as the basis, lengthened the frame, and installed an additional front axle completely identical to the standard one. Both axles turned synchronously through a system of steering linkages.
At the rear, instead of a body, they mounted a fifth-wheel coupling from the MAZ-504 tractor. Under the cab they placed the proven Yaroslavl YaMZ-236 diesel engine with an output of 180 hp, paired with a five-speed gearbox. The suspension remained classic — leaf-spring.
The calculated figures looked impressive. The tractor's curb weight was 6,790 kg. The fifth-wheel load reached 10.5–10.9 tons, whereas on the production MAZ-504 it did not exceed 7.7 tons. The semitrailer could weigh up to 27 tons, and the gross combination weight reached 34,150 kg.
Similar solutions had already been used abroad. The Mercedes-Benz LP333 had been produced since 1958, the FIAT 690 appeared in 1963, and in the United States similar layouts were tested by GMC. The Minsk engineers were not copying directly, but moving in parallel with global trends.
Visually, the truck tractor with two steering axles looked unusual and even defiant.
Testing: a chronicle of malfunctions
The test run stretched over a year and totaled 12,867 kilometers. A detailed "Report on Experimental Work No. 481-65," 58 pages long, has survived in the archive, and today it reads like the story of a lingering illness.
At the 2,240 km mark, it became clear that the engine was developing insufficient traction. A check of the fuel system showed that the injectors were operating at a pressure of 160–170 kg/cm² instead of the standard 150, and fuel delivery was below specification. After adjustment, testing continued.
By 3,290 km, the engine seized during startup. Disassembly revealed sticking exhaust valves in the guide bushings of the left cylinder head. The fault was corrected, the engine was reassembled, and the vehicle was sent back onto the route.
The report dated October 15, 1964, was signed by six specialists, including the head of the powertrain design bureau A. Futa and research engineer Yu. Murokh. The document was approved personally by Mikhail Vysotsky.
However, the main problems were not related to the engine. In turns, the tractor began to "wander." Two steering axles required exceptionally precise synchronization of the steering linkages: the slightest discrepancy in adjustment led to jerky vehicle behavior. Minsk specialists had no such experience at the time, and the testers noted a "stubborn handling character" in their reports.
The project's fate was finally decided by off-road runs. When turning, the six wheels laid three tracks at once instead of the usual two. On asphalt this was barely noticeable, but on soaked dirt the tractor began to literally dig itself in. Where an ordinary two-axle MAZ passed without problems, the MAZ-520V got stuck.
Why the project was closed
The formal factory conclusion looked cautious. The weight figures were deemed satisfactory, and the dynamics as well. The recommendations stated: continue testing until a mileage of 25–30 thousand kilometers.
But the decision was made at another level. The economic calculation proved merciless: for the same money, two standard trucks could be produced. Together they carried a greater total volume of cargo, were easier to repair, and their spare parts were standardized across the country.
The export argument also failed. Finland remained too narrow a market to rebuild the assembly line for it. Let the trucks operate there underloaded — that approach was considered more rational.
The project was discontinued. The only built MAZ-520V was, apparently, dismantled for parts and assemblies.
What remained of the idea
The concept itself did not disappear. The layout with two steering axles at the front and one driven axle at the rear is still used in Japan and China — where trucks operate mainly on good roads.
Europe, however, took a different path. Lift axles, or "lazy axles," became widespread: the additional axle is lowered only under load and remains raised when empty. Such a system does not require complex steering synchronization and is cheaper.
The Minsk Automobile Plant also experimented in this direction. The MAZ-516 with a liftable third axle was produced in limited series, mainly for export. Within the country, the design was considered unnecessarily complex.
The MAZ-520V remained a rare technical curiosity — a truck that deliberately went against established layouts. At the same time, the engineering logic of the project itself was sound. Today, such three-axle vehicles successfully operate in Asia, carrying heavy loads. The Minsk designers were essentially right, but mistaken in timing and circumstances.