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How to check the geometry of the car body

September 21, 2019

When the car leaves the factory assembly line, its body is completely symmetrical, that is, it has the correct geometry. It allows to arrange also symmetrically and all details and elements of a car, attached to the car carrier frame.

As operation, details, which form the skeleton of the car, though, that they are at first rigidly bound together, gradually shifted. It happens, not a little, when there is significant mechanical damage to the car as a result of an accident. In any case, the geometry of the body of the "old" car to a greater or lesser extent is usually violated.

The broken symmetry of a automobile framework is shown in what, starting from the formation of non-standard gaps between the door and the body, to serious problems with the controllability of the car while driving. You can imagine, to what it can eventually lead. Therefore, checking the geometry of the body is important, and not only when buying an old car, but also in the operation of their own.

Check the geometry of the body

There are several ways to determine the presence of body shifts. There are less accurate methods, which are used at home, and more informative, used at high-tech service stations. But, before determining the degree of displacement of body parts, should be considered in more detail, which carries the definition of the geometry of the car body.

What is the essence of body symmetry and the main reasons for its violation

A section can be found in the technical support for each car, where the distances between certain points on the body. That is, the manufacturer provides, that these indicators must be constant for the normal operation of the same door mechanisms, adjustment of disorder-convergence, tight fit of the hood and rear doors.

Basic dimensions, changes which directly indicate a violation of body geometry are as follows:

  • width of front and rear tracks;
  • wheelbase length (wheelbase);
  • the distance between the spars and their length;
  • the sizes of certain diagonals of apertures of windows and doors, motor department, trunk and cabin.

But the most important are always the distances between the mounting points on the base of the car (spars) its chassis elements, such, like glasses. Side members are the basis for mounting many automotive components and mechanisms, the work of which may be disrupted by the displacement of the main load-bearing elements of the car frame.

Longerons

Of course, the main reason for the violation of the geometry of the body are usually mechanical actions. Of course, that at a frontal blow first of all the sizes of an engine compartment considerably change. However, with, although to a lesser extent, the distances between other checkpoints will also change, even such, as the back track. That is, at considerable mechanical damages practically all control distances change, but to varying degrees.

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The second main reason for the shift of body parts, this is often far from ideal pavement. In this case, the control points are shifted gradually, slightly and much more evenly.

Signs of broken geometry, are determined without measurements

It is wrong to think, that small skews of the car frame can be ignored. After all, it is better to correct body deformations earlier, than to wait, when significantly mishandled car parts can lead to poor handling, which can cause very deplorable situations on the road. What can indicate that, that with the car frame there were spatial changes? The initial signs are as follows:

  • the door does not close clearly (it is necessary to exclude their possible sagging on loops);
  • worse and slamming hood and trunk.

These "symptoms", especially if they appeared at the same time without the involvement of significant damaging factors, should make the motorist think, that the body for some reason led. Moreover, the degree of violation of the body shape will progress, if you do not eliminate the cause in time and do not restore the proper symmetry of the car.

Violation of body geometry

If you do not intervene in time, the following symptoms will appear, which indicate that, that the geometry of the body is not changing for the better. The car will start to lose control at first at high speeds, and then on average with a perfectly working chassis. This will indicate the curvature of the glasses, side members and other structural elements of the car body.

If the motorist is not indifferent to his car, as well as for their own safety, noticing the first signs of deformation of the frame, it is necessary to carry out measurements of control sizes, which can be done less accurately, but on their own, or with a high degree of accuracy, however at the WTO.

Check the body geometry yourself

As mentioned above, in the technical support you can find the section, where checkpoints are specified, changing the distances between which signal the violation of the desired shape. Now it is even easier for motorists, because the layout of control labels for any car model can be found on the Internet, if the "book" is missing for some reason.

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Used as a measuring device:

  • special scale rail;
  • caliper;
  • roulette.

Measurement of body geometry

Measurements with the first two instruments are more accurate. However, they are not always available, therefore more often in house conditions apply a usual roulette.

Door openings and interior dimensions, the trunk and bonnet space of the car usually cannot be measured. Here the deformation is determined by the visual conformity of the fit of the body parts.

It is much more important in terms of diagnostics to measure the distances between the control points of the base of the car body. Before, how to check the geometry of the body, the car should be placed above the manhole, to facilitate access to the desired points. This should be taken into account, that to measure some control distances it is necessary to remove some interfering details. Here it is important to measure and evaluate the difference:

  • wheelbases on both sides;
  • diagonals between control points;
  • transverse distances between the wheels of one axle.

Differences between the obtained data and those sizes, which are specified in technical support to a car, indicate the presence of body deformations, and to their degree. Based on the results of such measurements, we can conclude that the body needs to be repaired, as well as the urgency of such an event.

Often such measurements are practiced when buying old cars, to evaluate, whether there were serious injuries before. If the car was in an accident, even after repairs, there is usually a mismatch of the basic dimensions. Although, with, visually inconsistencies of body parts are not revealed.