How to replace a spar with your own hands

Design Features

So, we figured out that the spar is a simple pipe with a rectangular cross-section. Depending on the engineers’ ideas, they:

• are located in front and behind the car.
• extend along the entire length of the housing structure.

Due to the fact that various forces are constantly pressed on the side members, they must withstand serious loads: this includes the weight of the engine, the weight of people in the car, as well as a host of other automotive parts. Also, this part is constantly subject to shock load, which is transmitted from car wheels while driving.

If you look at the photo of the inside of the car, you will see that the frame frame looks like a ladder frame, similar to the letter "P", including the rear one. Ladder frames are commonly used for SUVs, crossovers, and trucks. Passenger cars are most often equipped with a load-bearing body structure.

Tasks of spars

The spar in a passenger car serves as a reinforcing part for the underbody, mudguards and luggage compartment floor. In large cars it acts as the main strength element of the body. In addition to its reinforcing task, the front spar acts as additional shock absorbers - it is located in the deformation absorption zone. After all, in order for the part of the car body where people are located to receive the least impact while driving, it is necessary to soften the impact - and this impact is taken by the front side member.

To ensure that vibration spreads evenly throughout the body, engineers create “deformable” zones in its front parts. In the longitudinal direction they have a weak force structure. Now passenger car manufacturers are trying to make it as thin as possible: they reduce the thickness of the section or walls, create special holes in the “safest” places where less load is applied. Designers also use folds when stamping parts. They are needed so that during an accident the spar folds into an accordion and does not break. In a collision, the side members take the brunt of the impact, which is why they are often deformed. But such a sacrifice is justified: due to the absorption of kinetic energy, the force of the impact on the cabin is reduced. In trucks, both the rear and front side members suffer.

Problems related to spars

Under the influence of loads, the side members still deform over time, especially the front one (the load from the engine and its systems) suffers. Just like the front ones, the rear ones can crack and get tired. The word “get tired” implies the initiation of a crack, which over time grows throughout the entire part. Of course, an accident can also leave a significant mark.

What does operating a car with damaged side members entail? Some parameters of the car are violated: slightly, but the position of the doors, connectors of body parts, and the position of the power plant changes. The suspension geometry also suffers. Due to all these shortcomings, the car's handling is reduced. Therefore, if the body is damaged, you need to take the car for diagnostics - this decision will be correct.

If the spar completely bursts, then the entire body structure will be completely destroyed. It is because of this that after an accident, experts look at the degree of deformation of these elements. The position in which the side members are in the car also plays an important role.

Statistics: Approximately 90% of all work associated with this part occurs on the front spar. Such damage can be resolved quickly only with a frame spar - there it is simply replaced. As for the supporting body, sometimes the spars simply cannot be replaced. Let's say it was slightly dented in an accident: such damage can be corrected using a special carolin stand. For example, on the stand there are front left and rear side members - using a convenient location, mechanics measure all the parameters necessary to correct the problem.

It happens that the side members of a car are in such a state that the only option left is replacement. Changing parts entails a significant change in the properties of the entire body. After all, the shape, material and weight are calculated by the manufacturing company - in automotive centers you have to improvise. When the main parts of the spar are in good condition, a partial replacement is performed using arc gas welding.

What types of damage to side members occur?

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As we noted earlier, damage to side members occurs most often as a result of serious road accidents. Conventionally, this type of damage can be divided into three types:

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• mechanical damage
  associated with visual changes in the structure (deformation, curvature, etc.);
• internal damage
  (cracks, stress in the metal);
• violation of the integrity
  of the welded fastenings of the spar.

External damage is detected during visual inspection and control measurements. It is more difficult to identify internal stresses of the metal and the presence of cracks, but it is possible with the help of spectrographic study of the metal structure and photography in the infrared range.

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Video - extracting the spar of a Kia Sid car without a slipway:

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Unfortunately, as noted earlier, it is not possible to fully restore the spar, and therefore the motorist should pay close attention to whether there is any such damage when purchasing a used car. If the side members of the car were damaged and were later restored, it makes sense to refrain from purchasing such a vehicle.

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What is a spar?

A spar is a part of the body designed to strengthen the structure of a car. Suspension parts or beams are attached to the spar. The side members are located on the sides of the car, front and rear, and they bear the entire main body load of the car.

Initially, a spar was a name given to a reinforcing part of a car’s frame, since the frame was the supporting structure of the first cars. Gradually this part moved to the car body and became part of it.

Among the failures of the side members, it is necessary to note the appearance of cracks or corrosion of the metal. If small cracks appear, the spar can be repaired using a welding machine. However, if a strong split in the structure is noticed, then the spar must be replaced and this work should be entrusted, best of all, to professionals.

If cracks on the side members or traces of corrosion are not detected in a timely manner, it is recommended to take urgent measures to eliminate this malfunction, since these problems can lead to the fact that the car may simply fall apart on the road and then it will become very difficult not to get into an accident.

Advantages and disadvantages

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The use of side members in the design of car bodies and the departure from the traditional frame body layout has a number of advantages with a relatively small number of disadvantages. The advantages of using spars include:

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• a sharp reduction in the weight of the body and the vehicle as a whole;
• providing greater torsional rigidity and, as a result, better car handling;
• relative simplicity of design;
• high safety of this type of body in the event of a traffic accident.

However, despite a number of significant advantages, spars also have a significant drawback - very limited recovery options in case of deformation .

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This is due to the fact that the front and rear side members are tightly attached to the body using welds. The stiffness parameters of the spar and the degree of resistance to loads are clearly calculated by the automaker. For this reason, restoration of the spar after any significant damage (a similar situation is not uncommon in the case of an accident) leads to the fact that the part changes its strength characteristics and is not able to fully fulfill its “responsibilities” to ensure body rigidity.

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Video - extracting the side members of a Volkswagen Tiguan:

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At the same time, it will also not be possible to weld a new spar due to design features. In fact, if the side members are damaged, any repair becomes very limited, and factory performance is significantly degraded.

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Front spar - DIY replacement

Among the reasons for the failure of the front spar it is worth noting:

• Poor quality of road surface
• Loose suspension or steering mounts
• Driving at high speed on poor-quality road surfaces

Replacement procedure

1. Remove the door using a power screwdriver. Remove the mats and soundproofing material.
2. Remove the fender and secure the front part of the body from possible falls and movements. The front axle beam is also subject to fixation.
3. Pull the springs and unscrew the 3 bolts from the upper ball joint. Then remove the upper arm. Note. It may happen that the bolts on which the spar is secured are jammed and do not give way. In this case, you are allowed to get rid of them in any way, including an angle grinder.
4. Unscrew the brace, which is designed to secure the spar and beam. Then cut off the engine mudguard with a grinder.
5. Divide the side member into two parts and separate it from the body by sawing it behind the beam.
6. Clean the mounting points from dust, dirt and traces of corrosion and install a new spar in this place. All bolts that stick out from it must be tightened thoroughly.
7. After this, the entire lower part and the engine mudguard are subject to welding.
8. Reassemble all front suspension components in reverse order and do not forget to bleed the brakes.
9. Reinstall the fender and door.

Replacement algorithm

To remove the side member (VAZ 2110), follow the instructions:

• remove the door using a screwdriver;
• Raise rugs, heat and sound insulation;
• in the area where the splash guard is located, clear the surface of flammable products;
• remove the car fender;
• secure the VAZ to the front on stands;
• install the beam on the bridge in front to prevent displacement;
• dismantle the springs, remove several fasteners from the ball and remove the lever;
• if the fasteners between the timber and the beam cannot be removed, cut them off using a grinder;
• unscrew the brace on the beam and cut the mudguard;
• divide the product into 2 parts and dismantle it from the body by making a cut behind the beam;
• After cleaning the fasteners, proceed with the installation of a new longitudinal beam.

How to change the rear spar

Replacement of the rear side member of a VAZ 2110 is carried out in case of visible damage, as well as after an impact in the rear of the car. Of course, the old spar can be straightened or welded, however, after the rapid aging of the metal, it loses its load-bearing capabilities and driving becomes difficult. In addition, rubber wear increases due to body deformation and displacement of suspension parts.

Replacement procedure:

1. Raise the rear of the car using jacks and place it on strong supports. Consider the location of the work site and do not place supports exactly there.
2. Carry out work to correct the proportions of the body. To do this, hydraulic struts are installed under the bottom and support the spacer from the ceiling. Then use pressure to correct the bent body parts.
3. Remove the rear fenders.
4. Now you need to remove the rear suspension elements. To do this, you can place the car on its side and place tires under the part being laid. To prevent the vehicle from tipping over, install reliable supports. After completing dismantling, clean the surface of the part being replaced from dirt and debris.
5. The old spar is removed as follows: holes are drilled along the lines of the weld seam (the diameter of the drill must correspond to the diameter of the welding point), the places that could not be drilled with a drill are cut off with a grinder, and all the rest are cut off with a chisel. After dismantling the spar, straighten the body defects using a mechanic's hammer and clean the area of ​​the future spar with a grinding wheel.
6. Try on the new part against the body, trim off the excess. Drill it in 3 places at the site of the future weld. Then secure it in place and tack it with 3 points in the pre-drilled holes. After this, weld metal plates on the outside and inside of the seams to strengthen the structure. After this, completely weld the new spar to the body.
7. Clean the welding areas with a grinding wheel and treat the seams with epoxy resin.
8. All metal parts must be coated with two layers of primer.
9. Reassemble the rear suspension in the reverse order and install the car on the wheels.

This completes the replacement of the side members. If you decide to carry out such work yourself, be sure to study the welding manual, because an incorrectly welded spar may sooner or later come off and the structure will lose its reinforcing properties. Thus, the car may fall apart while driving, and this, at a minimum, is not safe.