Conversion of MMZ 81021 trailer to springs

The MMZ trailer has been in serial production since 1972. The device is designed for transporting various types of cargo and tourist equipment. The base tractor for this unit is the VAZ-2101. Both vehicles have the same components: tires, shock absorbers, bearings. The MMZ trailer can be used in conjunction with other passenger cars of domestic and foreign production, which are equipped with a standard towing unit.

Device

The towbar under consideration includes the following parts in its design:

• Frame and drawbar.
• Awning with arches.
• Body.
• Chassis.
• Lock.
• Support stands.
• Electrical equipment.
• Alarm system.

The frame of the MMZ trailer is made of steel by welding. It consists of a pair of longitudinal beams and three transverse elements. The spars have a trapezoidal cross-section (50/32/25 mm) and are made of steel. A locking device is welded in the front part of the converging side members. In the middle there are brackets on which the suspension springs and hydraulic shock absorbers are mounted. The rear cross member is equipped with buffer and support strut mounts. In addition, holes are made in the frame for bolting the body.

Suspension

Suspension elements are installed between the axle and the frame, which reduce vibrations that occur when the trailer moves over uneven road surfaces. The suspension consists of a spring and a shock absorber installed on each side of the axle. To secure the shock absorber housing, there are two reinforcing elements installed between the upper mounting point of the shock absorber housing and the trailer frame. The shock absorber is installed inside the spring.

To protect against sharp impacts during suspension breakdown (full travel of elements), there are conical rubber buffers installed on the frame. They rest against the counterpart on the axle and, due to the deformation of the rubber, absorb the impact energy. There are two longitudinal rods to connect the axle to the frame. There is another transverse rod that serves as a stability stabilizer. All elements are assembled on threaded connections, many of which have safety cotter pins. Over time, these connections rust, and disassembling these units is very problematic.

The structure is based on a welded frame weighing 27 kg. This element is the most critical component of the MMZ-81021 trailer and serves to install the suspension and cargo platform. The frame has a reciprocal towing device that fits onto the towbar ball. All electrical wiring is routed along the frame elements.

Structurally, the part is non-separable and if deformed or damaged, it must be replaced. It is prohibited to operate a trailer with a frame that has cracks or tears. There are three support supports on the front of the frame and the rear cross member, which are used when storing the trailer in the uncoupled state. Additional fixation is provided by wheel chocks included with the trailer.

A coupling device is installed on the front part of the frame, equipped with a chain guard and a spring-loaded crimp device.

Characteristics of MMZ trailers

The body part is made of steel by welding. The bottom and sides are made by stamping from sheet steel (0.7 mm). Wheel niches are located inside the body near the side walls. The floor is covered with a rubber corrugated cape. The upper frames of the sides are equipped with sockets for mounting awning arches, which are pipes of a certain diameter. The awning itself is made of tarpaulin, fixed to the arches using a special cord, which is threaded through eyelets located along the edges of the canvas.

The lacing is carried out between the eyelets and thrown onto the strapping hooks, which are welded to the sides. The chassis of the MMZ trailer consists of the following elements:

• Wheels with VAZ-2101 type tires.
• Tubular axle with axles welded at the edges.
• Transverse and longitudinal rods.
• Spring suspension mechanism.
• Telescopic type hydraulic shock absorbers.
• Shock absorber fixing brackets.
• Rubber buffers.
• Otboynikov.

Loading platform

At the base of the platform there are four timbers of a non-interchangeable design. The platform itself has an all-metal design and is attached through bars to the frame. The fastening elements are bolts and washers. These attachment points often become hot spots for corrosion. The tailgate of products manufactured before 1986 had a solid design. Later, a small folding section appeared in it.

To install the awning, four standard arcs and one 9-strand linen rope with a diameter of 5 mm are used. This rope is used to tighten and secure the awning along the sides of the trailer. Three removable rubber mats are placed on the floor of the platform. When using the trailer, they should be removed to dry the platform floor.

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The big disadvantage of the MMZ-81021 trailer platform is the wheel niches, which narrow the useful width of the trailer in the central part. Another disadvantage is the continuous tailgate, which limits the maximum cargo length. Although this problem is not currently relevant, since it is easy to find and rent a truck with any platform length. When the metal of the platform floor is destroyed, it gradually separates from the frame, which can cause the trailer to tip over. During operation, it is necessary to monitor the condition of the fasteners and periodically tighten the connections.

Equipment

The MMZ passenger trailer is equipped with three support legs. They are mounted on a platform to block the suspension springs. The electrical equipment of the device is of a single-wire type, powered by the vehicle's on-board voltage of 12 V. It also includes a pair of tail lights, a license plate light, and a set of wires with a plug.

The rear light elements are of a two-chamber type (in the upper compartment there is a single-filament turn signal lamp, and in the lower part there is an analogue with two threads, indicating the brake light and dimensions).

State license plates for a car trailer

The cost of license plates for a car and a trailer is exactly the same.

The need to pay state duty is established by the Tax Code of the Russian Federation. Today, automakers selling their products on the territory of the Russian Federation must equip their vehicles with special seats where the license plate is attached.

Moreover, certain requirements are established for the location of such a number. Usually, the location for attaching the license plate to the vehicle is quite easy to determine.

These are usually the front and rear bumpers of the car. The situation is similar with factory-made trailers. Sometimes standard seats are simply not available.

For example, if the trailer comes from another country and the installation standards there are slightly different. In this case, it is still necessary to follow the regulatory documents, which reflect information about the mounting location -. The following recommendations are given regarding the location of the sign itself:

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Peculiarities

The front side of the MMZ trailer is equipped with a pair of reflective reflectors of a round configuration and a white color scheme. At the rear there is a pair of red triangular reflectors. In 1986, the board began to be made collapsible, and new reflectors appeared. Improved variations received a rear-biased axle, smaller wings, and mudguards. Later they began to produce models without bumpers, instead of which there were simply two protrusions, options with updated optics and different combinations of reflectors. The frame number is located on the right under the folding part of the side.

Modification of MMZ trailer

Below is one way to modernize the device in question. The essence of tuning is to dismantle the body and replace all elements to the maximum. Initially, we install a new lock, then sandblast and paint the sides. The main process includes the following steps:

• Replacement of rear shock absorber rubber bands with bushings.
• If these elements are suitable for further use and do not show signs of deformation, it is better to leave them, especially if they were made during the Soviet Union.
• As spring mechanisms, you can install analogues from Oka or Zaporozhets (if a constant and maximum load is provided). In the second case, you will need to purchase spring ties.
• Parts from a VAZ-2101, Moskvich or Niva are suitable as rear shock absorbers.
• For fastening, use 12*60 mm bolts.
• The wooden cross members under the body can be replaced with a metal profile.

If the tires rub against the springs, use an additional spacer from the VAZ-2101 brake disc.

Modernization

Trailers for passenger cars, the price of which starts at $200 (depending on the condition of the “cart”), can be improved in one more way. Stages of work:

• Replacement of the coupling device with a new version.
• The hubs and handbrake are installed.
• From an ordinary jack you can make an additional support on the drawbar.
• Next, the headlights are replaced (you can buy new elements or use existing headlights, for example from a VAZ-2108).
• The structure is sheathed with galvanization.
• Further modification of the MMZ trailer consists of restoring the suspension. To do this, we replace the hubs with plates from the VAZ-2108 (from a bent beam).
• The frame is strengthened.
• The structure is being painted.

Total information

One of the first serial products developed specifically for the products of the VAZ plant was the MMZ-81021 trailer. Production started in 1972 and was carried out at the production facilities of the machine-building plant in Mytishchi. The main feature of the trailer was the wide unification of parts with Zhiguli cars, from which the wheels, tires, wheel bearings, and suspension elements were borrowed. Thanks to this, repairs to the vehicle and trailer while on the road could be carried out using the same tool. At the same time, there was no problem with the search and selection of spare parts and components.

An important characteristic of the MMZ-81021 was a unified towing device, which made it possible to operate the trailer with any vehicle. A big plus was the significant dimensions of the cargo platform, which were almost 1.85 meters long and 1.6 meters wide. Due to the sides with a height of 45 cm, it was possible to place a significant amount of cargo, the weight of which should not exceed 135...285 kg (depending on the make of the car). The tarpaulin awning on the MMZ-81021 was installed on special arches, which were included in the standard equipment of the trailer. Due to the awning, the useful internal volume of the trailer was 1200 liters, which was a very good indicator.

Technical specifications

Performance characteristics of the tow hitch in question:

• Total weight – 300/450 kg.
• The mass of transported cargo is 135/285 kg.
• The maximum speed when coupled with a car is 80 km/h.
• Length/width/height – 2.6/1.6/1.02 m.
• Ground clearance – 25.8 cm.
• Wheel track – 1.34 m.
• Platform area – 2.12 sq.m.
• Dimensions of the internal part – 1./1.5/0.38 m.
• The connection is of the ball type.

Model differences

The trailer could be used by small (VAZ, IZH and AZLK) and medium (Volga) class cars. According to the MMZ-81021 operating manual, the maximum load for machines of the first category should not exceed 135 kg, and for the second - 285 kg.

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At the same time, the trailer itself was identical and had a structural weight of 165 kg. Due to proper weight distribution, the maximum load on the coupling device did not exceed 50 kg. The use of a trailer imposed restrictions on the maximum speed of the road train, which should not exceed 80 km/h.

Recovery

Repairing an MMZ trailer can be done as follows (the original model was practically coming apart at the seams):

1. Resuscitation begins with careful straightening of the body and sealing all cracks by welding. Next, the diagonals are checked, the sides are pulled together with soft rolled wire and the corners are further strengthened. A couple more amplifiers are welded onto the bottom part. This operation is due to the fact that in the standard version the bottom is equipped with only one amplifier, which is not enough for full operation. As a result, the metal breaks and the bottom simply falls through.
2. You can use improvised means to weld a new body bottom as an additional layer on top of the main element. Several pieces of iron 3 mm thick are quite suitable for this purpose. To begin with, the segments are welded together and then with the main coating. For reliability, the entire structure is fixed with bolts and press washers.
3. We install reinforced springs.

After restoration, the MMZ-81024 trailer was subjected to increased loads (transportation of cement, sand, crushed stone). After 4 months of use - no complaints, even compared to the new model.

Negative reviews

The comment is given about the standard trailer MMZ-81021. Owners note the small body size of 180*160 mm, while inside there are huge niches for wheels. It is not very convenient to carry it, since only the middle part of the rear door opens. The ultimate dream is to transport 3-meter boards. There is also practically no place to place furniture, due to the same wheel arches.

The frame is weak and deforms even with a slight overload. The springs are also not very strong, and the short drawbar does not allow for normal backing. The result is an inconvenient design, suitable only for transporting fruits and vegetables.

Tow hitch

VAZ and AZLK cars that rolled off the assembly line never had a standard towing device (towbar). This unit was installed by the owners themselves, purchasing the product separately. For towing the MMZ-81021 trailer, the Mytishchi plant produced two types of devices that differed in the method of attachment to the power elements of the bodies.

One device had catalog number 11.2707003 and was intended exclusively for products from the Tolyatti plant. The second, number 12.2707003, was for “Muscovites”. The ball parts and sockets of the devices were the same. The differences were in the wiring harness from the socket, with the help of which it was integrated into the vehicle’s on-board network.

Competitors

In order to choose a good trailer for a passenger car, the price of which depends on many factors, you should pay special attention to the manufacturer. The durability and practicality of the device depend on the quality of the components and materials, as well as the quality of the device’s painting.

Towbars from the Moscow company MZSA have received good reviews. The model line includes products with aluminum or steel sides, additional protection, large caps, and enlarged sides. The manufacturer also offers specialized designs for transporting boats, boats and other small vehicles. A distinctive feature of this manufacturer is the powder coating method using metal and ceramic inclusions. This provides excellent reliability and safety.

Purpose

The first serial trailer from MMZ was the immortal model 81021. It was created specifically for installation on VAZ cars.

Initially, the model was developed as a tow hitch for the VAZ 2101, that is, the Soviet Kopeyka. It is not surprising that the vehicles received similar shock absorbers, identical bearings and even identical wheels. In fact, all the components of the chassis for 81021 were already there. All that remains is to install them on the body and make some modifications. Thus, the plant came up with an ideal partner for Kopeyka, which the owners of these cars immediately took advantage of. They started buying 81021 very quickly and actively.

If we talk about the dimensions of the pioneer, they were 1850x1600 mm. This made it possible to transport all kinds of cargo, making the trailer universal and multifunctional. The design provided for a side with a height of 450 mm and an awning, which was installed on a metal frame. As a result, the total volume of the MMZ was about 1200 liters.

Soon trailers began to be adapted for use on vehicles of other smaller classes. They were intended for cars that were then produced by factories such as AZLK, VAZ and IZH.

Interestingly, the trailer from MMZ, intended for AZLK, received the same design elements as those used on the vehicle itself. For such vehicles, the load limit was set at 135 kilograms. It should also be noted that the GAZ plant produced models for middle-class cars. That is, MMZ made trailers for the then elite and for many inaccessible Volga. The load on the coupling device was a good 50 kilograms, and trailers were allowed to be operated at speeds of up to 80 kilometers per hour.

At one time, 81021 was recognized as a necessary and extremely useful device. This was due to the fact that the trailer could perform several important functions.

Now on Avito and other portals you can find used trailers from different manufacturers, or purchase a new vehicle from a huge assortment. Back then the choice was limited.

But in fact, people did not need a huge choice. They were quite satisfied with the opportunities that MMZ provided them with. After all, with the help of their trailers it was possible to:

• deliver industrial goods;
• transport food;
• transport agricultural products;
• deliver construction materials.

Due to its versatility, MMZ has solved a number of transportation problems. The awning protected from dust and precipitation, the spacious body made it possible to transport fairly large quantities.

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Other manufacturers

Among the leading trailer manufacturers are . The company specializes in the production of heavy products aimed at transporting yachts, boats, and large industrial equipment. Recently, the model range has been replenished with lightweight modifications that can be equipped with an awning for an MMZ trailer. In addition, the manufacturer claims that, upon customer request, it can supplement the unit with all possible additional structures.

Also popular on the trailed equipment market are models from the Ukrainian enterprise “Kremen” (Kremenchug). The products are distinguished by a high margin of safety, as they are made of high-quality metal, thickened profiles and are equipped with a reinforced frame. The disadvantages of these devices include their heavy weight, which makes the trailer not very convenient. It is worth noting that the range of this manufacturer is limited to single-axle modifications with an average load capacity. Nevertheless, the company remains among the leaders in the relevant market.