Correct wheel alignment angles. Effect on the car's handling

The angles of wheel installation play a big role in the operation of the car - with proper observance they allow to increase the service life of various components, and also improve the comfort of driving. But at the same time, many do not understand how to comply with them and for what it is needed.

What does it influence?

Ideally, the wheel should always be installed strictly perpendicular to the roadway, and such wheel alignment angles allow maximum stability, and also provide minimum resistance. In addition, compliance with this rule reduces tire wear and fuel consumption, which also has a very positive effect on the operation of the car. But, unfortunately, such an ideal is impossible to achieve.

The angles of wheel installation are constantly changing in the process of changing road conditions, load or at various turns; therefore, several dozens of different parameters are placed in the car, which determine the most optimal position under different conditions. Most of these parameters are set as constant values, while other wheel alignment angles can be adjusted throughout the operation of the vehicle.

In modern foreign cars, the adjustment of only such a parameter as the convergence of the wheels, but with such a seemingly positive side, there are minuses. For example, if due to physical damage the geometry of the body or the chassis is disturbed, adjustment of the wheel alignment angles can be carried out, and if only the convergence is adjusted, a complete replacement of the affected parts must be made, which are often not so cheap.

Angle of slope

Measured between the vertical and the line that passes through the center of rotation of the ball bearing, as well as the bearing of the support of the telescopic pillar in a plane parallel to the longitudinal axis. It helps to stabilize the steering wheels, that is, it allows the car to move straight, if the driver does not hold onto the steering wheel. For a clear understanding of the caster, remember a motorcycle or a bicycle, in which the steering column always tilts backwards, which means that when driving, if the angle of the wheels is not adjusted, they constantly try to return to the forward position.

It is due to the caster, if the driver does not hold onto the steering wheel, the car goes straight, and after the turn it automatically returns the wheels to the standard position. If you change the angles of the installation of the front wheels, then the car will be more difficult to control, because you need to steer constantly, and this is quite a tedious task not only for the driver, but also for his tires, which wear out quickly enough. If you increase the caster, the car will start to travel along the road, as if on caterpillars, and the rotation of the rudder will require extremely heavy physical effort. Of course, all of the above applies more to rear-wheel drive vehicles in which the angles of the front wheels are adjusted slightly differently, because in the front-wheel drive a slight positive value of the caster is done in order to stabilize the wheels during coasting, as well as sudden side loads or braking.

If the angles of setting the steered wheels are not set correctly, the car will start to sidewise when driving, and the driver will have to apply considerable effort to turn his vehicle into the left and right sides.

Wheel camber angle

Measured between the vertical and the plane of rotation of the wheel. In other words, regardless of how the struts and levers are tilted during the movement or changing loads, the angles of setting the steered wheels in relation to the road must remain within the specified limits. In the event that the upper part of the wheel deviates outwards, the collapse is called positive, and if it is tilted inward, it is negative. If there are any deviations from the recommended angle of the wheel installation, the car starts to gradually move aside, and there is also an uneven wear of the tread.

Convergence

It is the angle between the longitudinal axis of the car and the plane of rotation of the wheel. Setting the angles of convergence of the wheels allows you to achieve the correct position at any speed and regardless of the angles of the car. If there is an increased convergence, then this causes a sawtooth wear of the outer part of the tread, while a negative angle affects the internal one in exactly the same way. It should be noted that if such problems occur, the tires can start to squeal in the bends, the handling of the car is significantly reduced, and fuel consumption is significantly increased, since there is an increased resistance to rolling of the front wheels, which also has a negative effect on the car's run-out.

In addition to the above, there are also angles, the occurrence of which is undesirable - these are the angles of motion, and also the displacements in one or several axes. If the motorist faces such problems, you need to send the car to the car service, where the professionals will check the corners of the wheels. "Nissan" and other high-quality foreign cars are also subject to similar problems, and if they are available, it is often necessary to repair the suspension or to restore the car body.

When and why is the adjustment carried out?

In most Nissan, VAZ and other cars that are not equipped with the McPherson suspension, camber for the front wheels often has a small positive value (0 to 45 ^degrees ), which reduces the effort on the steering wheel, as well as reduced gearing On the steering of all kinds of jerks. If the car uses the McPherson suspension, the wheels have a small or zero negative camber.

During operation, various parts of the suspension are exposed to natural wear, which is why the corners of the installation are violated. That is why from time to time (in accordance with the instruction) you need to measure the angles of installing the rear wheels and, if necessary, to adjust them.

Most often, "unplanned" adjustment is required for modern vehicles after hitting all kinds of pits or obstacles, as well as after participating in an accident that led to damage to the body. If you notice any changes in the behavior of the machine due to such cases, you should immediately send it to the SRT.

Among other things, it also happens that you have to go to the "razvalchikam" after the replacement parts of the suspension and steering, affecting the position of the wheels.

If you have not encountered any of the above cases, but you think that you have violated the parameters of the wheel alignment angles, then try to analyze the current situation and understand what could have preceded the change in the nature of the ride. For example, if you previously had other wheels, then in case of their imbalance, there may be vibration and uneven wear of the tread. It is also worth noting that, if the wheel bolts are not tightened sufficiently, the car can periodically shake, and in addition, tires with defects, different sizes, patterns and even the degree of pumping can also lead to abnormal behavior of your car on the road.

If the car takes you to the side, it often happens due to the braking of some wheel, as well as due to malfunctions in the brake mechanism, while broken shock absorbers have a negative effect on the behavior of your car on the road. A heavy rotation of the rudder is due to malfunctions in the hydraulic booster, and a reduction in run-out causes hub bearings.

Thus, it is far from always worth "sinning" at the corners of the installation of wheels. VAZ and other domestic cars are particularly prone to such faults, so it's best to begin checking with them.

Where to carry out repairs?

First of all, try to find a truly professional master, and do not try to find people with better equipment and stands. Service should be chosen in accordance with their needs, because otherwise you will overpay for what you really do not really need.

For example, if the machine is in good condition, and you just want to test and adjust the toe, you do not need to use the 3D wheel alignment set. A competent specialist will cope with such problems using a measuring rod and a standard lift, and with the same result will offer a much lower cost. If you want to test all geometry, then you really need specialized equipment.

What is the equipment like?

The stands on which the angles of wheel alignment are checked and their adjustment are divided into two main types - computer and optical. Each of the options is different for its features and benefits.

Optical

These stands are divided into two categories - laser and beam. In the latter, the incandescent lamp serves as a source of light. Two sources are fixed on wheels, and on the side and front of the car, measuring screens are installed, onto which a light beam is projected. When the corners of the car's wheels are adjusted, the beams are directed to the measuring rod in front of the machine. Laser, however, are more accurate, and it is more convenient for them to work for the master himself. On the sides of the elevator or pit, measuring screens are installed, in the center of which holes are made, through which the lasers are directed at each other. On the wheels are installed mirrors, with which the rays are reflected on the screens.

The advantage of optical stands is their simplicity, as well as reliability in use and a relatively small cost, but their shortcomings are quite significant. First of all, they are less accurate than computer ones, they can work simultaneously only with a certain axis of the car, and also do not provide for the possibility of using a special database of models in their work. Among other things, they do not have the ability to measure certain parameters that characterize the overall "geometry" of the car. Thus, if a multi-link suspension is used in a car, it is counter-indicative for checking and adjusting the angles of wheel mounting on optical stands.

Computer

This type of stands also has two subspecies - 3D and CCD (sensor). In the latter on each wheel fixed measuring heads, the data from which will be processed by a computer. According to the method used, connections between the heads of stands can be cord, as well as infrared wired or wireless. The latter type is currently the most common, but with the choice, one should also take into account the fact that to this day computer stands with an open loop are sometimes used, which are much worse in their functionality, in comparison with devices with a closed loop.

The advantages of computer stands are obvious: multitasking, extremely high accuracy, the ability to measure much more characteristics, and the use of a continuously updated database. It is also worth noting that in such equipment a specialized program is used that tells the mechanics the sequence of actions. But such stands are not without drawbacks - they have rather fragile sensors installed, and also they depend on the illumination and temperature conditions.

With the advent of computer 3D-stands there was literally a revolution in the field of checking and adjusting the angles of wheel installation. On the rack in front of the car a special camera is fixed, which allows to fix the position of plastic reflective targets on wheels with perfect accuracy. To measure the angles, it is enough just to roll the car back and forth literally for 20-30 centimeters, and then turn the steering wheel in different directions. After that, the information received from the cameras is carefully processed by a computer that gives out in real time all the necessary geometric parameters. This technology is called "machine vision" today.

Special attention should be paid to the fact that modern 3D-stands, unlike the others, do not require the car to be placed on a perfectly flat surface.

Subtleties of work

You can go to the alignment-convergence only if you have a faultless steering and chassis, and before the adjustment is carried out, the master must check these parameters. The machine rises on the lift, and then the specialist examines and moves the wheels, levers, traction springs and performs many other necessary actions.

The measurement is mandatory and, if necessary, the tire pressure is adjusted to the norm. If there is too much backlash or any physical damage to the parts, the specialist must necessarily stop the procedure and refuse the customer to carry out the adjustment if there is no way to fix the problem on the spot.

If, however, no deviations were found, the car is installed on a horizontal platform, and then loaded in full compliance with the manufacturer's recommendations. In other words, if the factory has specified the angles for a particular load, it will be a direct violation to try to adjust them on an absolutely empty machine. To install the suspension parts in the working position, first it will be pushed with effort, pressing down the rear and front part of the car. To avoid serious errors in the measurement process, pre-compensate for the runout of the discs is carried out, regardless of which stand is adjusted. To carry out this procedure, the master hangs an axle, the measuring devices are fixed to the wheels, and then they scroll. On modern 3D-stands compensation is carried out without hanging by rolling the machine in different directions for 20-30 cm.

How is the adjustment carried out?

Since all the corners of the installation are interconnected, when they are adjusted, professionals try to follow an extremely clear sequence. First, the castor is adjusted, and then the camber and convergence are changed. In the majority of modern foreign cars, only the last parameter is tuned.

The adjustment of the castor involves changing the number of washers, while the wheels of the car are braked by the working braking system (but not by the hand) - for this purpose, a specialized pedal lock is used in the workshops. In principle, the castor adjustment procedure is one of the most laborious for the "razvalchiki", it takes a lot of time, and so many do not like it. Some experts may even chop pucks with a chisel, while others just do not focus on the castor or try to convince their customers that this angle is in order, so it's always worthwhile to be watchful.

Adjustment of camber on the two-arm suspension is exactly the same as in the case of a castor. On the McPherson suspension, in most cases, the camber is changed by rotating a special eccentric bolt, with which the post is fixed to the pivot, but other options may be used. For example, on some models, instead of this bolt, a special slide mechanism is installed or the adjusting element can be placed in the base of the lever. There are also such structures in which the adjustment of camber is carried out by moving the ball joint.

Before adjusting the toe, the technician must pre-set the steering rack in the middle position , the handlebar should stand straight and fixed with a special lock. Adjustment is carried out by rotating the adjustment sleeve of the tips on each side (in any case not with one). One of the signs of a correctly performed operation is the direct position of the rudder without any distortions in the process of rectilinear motion. At least on this basis, you can always determine how well the adjustment was made and whether it really helped you to cope with the problems while driving.