The angles of the wheels play a big role in the operation of the car - if properly observed, they can increase the service life of various components, as well as improve driving comfort. But at the same time, many do not understand how to comply with them and why this is necessary.
What does this affect?
Ideally, the wheel should always be installed strictly perpendicular to the roadway, and such wheel angles allow maximum stability as well as minimum resistance. In addition, compliance with this rule can reduce 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 the wheels are constantly changing in the process of changing road conditions, loads or at various turns, so the designers put in the car several dozen different parameters that determine the most optimal position under different conditions. Most of these parameters are set as constant values, while other angles of installation of the wheels can be adjusted during the operation of the vehicle.
In modern foreign cars, it is completely envisaged to adjust only such a parameter as the convergence of the wheels, but this seemingly positive side has disadvantages. For example, if the geometry of the body or chassis is violated due to physical damage, then the wheel alignment angle can be adjusted, but if only the toe is adjusted, it is necessary to completely replace the damaged parts, which quite often are not so cheap.
Tilt angle
It is measured between the vertical and the line that passes through the center of rotation of the ball joint, as well as the bearing of the telescopic support in a plane parallel to the longitudinal axis. It helps to stabilize the steered wheels, that is, it provides an opportunity for the car to move straight if the driver is not holding the wheel. For a clear understanding of the caster, remember a motorcycle or a bicycle in which the steering column always tilts back, which is why during the movement, if the angle of the wheels is not adjusted, they constantly tend to return to the straight position.
It is at the expense of the caster, if the driver does not hold the steering wheel, the car goes straight, and after turning it starts to automatically return the wheels to their standard position. If you change the installation angles of the front wheels, then in this case it will be more difficult to drive a car, since you need to constantly steer, and this is a rather tedious task not only for the driver, but also for his tires, which wear out quite quickly. If you increase the caster, the car will begin to ride along the road, as if on tracks, and the rotation of the steering wheel will require extremely heavy physical effort. Of course, all of the above applies more to rear-wheel drive cars, in which the angles of installation of the front wheels are regulated slightly differently, because in front-wheel drives a slight positive value of the caster is made in order to stabilize the wheels during coasting, as well as when sudden side loads or braking occur.
If the installation angles of the steered wheels are not set correctly, the car will start to move sideways while driving, and the driver will have to make significant efforts to turn his vehicle to the left and right sides.
Camber angle
It is measured between the vertical and the plane of rotation of the wheel. In other words, regardless of how the racks and levers tilt during the movement or change of loads, the installation angles of the steered wheels relative to the road should remain within the specified limits. In the event that the upper part of the wheel deviates outward, the camber is usually called positive, and if it is tilted inward - negative. If there are any deviations from what the recommended wheel alignment data are, the car gradually starts to move to the side, and uneven tread wear is also observed.
Convergence
It is the angle between the longitudinal axis of the car and the plane of rotation of the wheel. Setting the convergence angles of the wheels allows you to achieve the correct position at any speed and regardless of the angle of rotation of the car. If there is increased convergence, then this causes a sawtooth wear on the outer part of the tread, while a negative angle affects the inside in the same way. It is worth noting that when such problems occur, tires can start screeching in corners, the car's handling is significantly reduced, and fuel consumption is also significantly increased, since there is increased rolling resistance of the front wheels, which negatively affects the car's mileage.
In addition to these, there are also angles whose occurrence is undesirable - these are the angles of movement, as well as displacements in one or more axes. If the motorist is faced with such problems, you need to send the car to a car service, where the angles of the wheels will be checked by professionals. Nissan and other high-quality foreign cars also face similar problems, and if they are available, they often have to repair the suspension or restore the car body.
When and why is the adjustment done?
In most cars of Nissan, VAZ and other brands that are not equipped with McPherson suspension, the camber for the front wheels often has a small positive value (from 0 about to 45 about ), which reduces the effort on the steered wheel and also reduces gear on the steering of all kinds of jerks. If the car uses McPherson suspension, then the wheels have a small or zero negative camber.
During operation, various parts of the suspension are subject to natural wear and tear, as a result of which installation angles are violated. That is why from time to time (in accordance with the instructions) it is necessary to measure the installation angles of the rear wheels and, if necessary, to engage in their adjustment.
Most often, “unscheduled” adjustment is required for modern vehicles after hitting various 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 service station.
Among other things, it also happens that you have to go to the "breakers" after the suspension and steering parts have been replaced, affecting the position of the wheels.
If you have not encountered any of the above cases, but you think that you have impaired wheel alignment, then try to analyze the current situation and understand what could have preceded a change in the nature of the ride. For example, if you previously had other wheels, then if they are unbalanced, vibration and uneven tread wear may appear. It is also worth noting that with insufficient tightening of the wheel bolts, the car may occasionally 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 leads away, this often happens due to the braking of a wheel, as well as due to malfunctions in the brake mechanism, while broken shock absorbers negatively affect the behavior of your car on the road. Heavy rotation of the steering wheel occurs due to malfunctions in the hydraulic booster, and a decrease in the stick out is the cause of the wheel bearings.
Thus, it is far from always worthwhile to “sin” on the angles of the wheels. VAZ and other domestic cars are especially prone to such malfunctions, so it is best to start checking with them.
Where to carry out repairs?
First of all, try to find a truly professional craftsman, and do not try to look for people with the best equipment and stands. The service should be chosen in accordance with your needs, because otherwise you will overpay for what you really don’t really need.
For example, if the car is in good condition, and you just want to check and adjust the toe, you do not have to use a 3D-stand for setting the wheel angles for this. A competent specialist will completely 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 check all the geometry, then you really need specialized equipment.
What is the equipment?
The stands where the wheels are checked for angles and their adjustment are divided into two main varieties - computer and optical. Each of the options differs in its features and advantages.
Optical
These stands are divided into two categories - laser and beam. In the latter, an incandescent lamp acts as a light source. Two sources are mounted on wheels, and measuring screens are projected on the side and front of the car onto which a light beam is projected. When the angles of the wheels of the car are adjusted, the rays are sent to the measuring rod located in front of the machine. Laser ones are more accurate, and it’s more convenient for the master to work on them. Measuring screens are installed on the sides of the elevator or pit, in the center of which holes are made, through them the lasers are directed at each other. Mirrors are installed on the wheels, with which the rays are reflected on the screens.
The advantage of optical stands is their simplicity, as well as reliability in use and relatively low cost, but their disadvantages are quite significant. First of all, they are less accurate, in comparison with computer ones, they can work simultaneously only with any specific axis of the car, and also do not provide for the possibility of using a special database of models in the work. Among other things, in them there is no way to measure some parameters that characterize the general "geometry" of the car. Thus, if a multi-link suspension is used in a car , checking and adjusting the wheel alignment angles on optical stands is contraindicated.
Computer
This type of stands also has two subspecies - these are 3D and CCD (sensor). In the latter, measuring heads are attached to each wheel, the data from which will be processed by a computer. According to the method of connection between the heads, the stands can be cordless, as well as infrared wired or wireless. The latter type is currently the most common, but when choosing, you should also take into account the fact that to this day computer stands with an open loop are sometimes used, which in their functionality are much worse compared to devices with a closed loop.
The advantages of computer stands are obvious: multitasking, extremely high accuracy, the ability to measure much more characteristics, as well as the use of a continuously updated database. It is also worth noting that such equipment uses a specialized program that tells the mechanics the sequence of actions. But such stands are not without drawbacks - rather fragile sensors are installed in them, and they also depend on lighting and temperature conditions.
With the advent of 3D computer stands, there has literally been a revolution in the field of checking and adjusting wheel alignment angles. A special camera is mounted on the rack in front of the car, which allows you to fix the position of plastic reflective targets on wheels with perfect accuracy. To measure the angles, it’s enough just to drive the car back and forth literally 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 provides in real time all the necessary geometric parameters. This technology is today called "machine vision."
Special attention should be paid to the fact that modern 3D-stands, unlike the others, do not provide for the need to place the car on a perfectly flat surface.
Subtleties of work
It is possible to go to the wheel alignment only if you have a working steering and running gear, and before the adjustment is made, the master must check these parameters. The machine rises on a lift, and then a specialist inspects and moves the wheels, levers, traction, springs and performs many other necessary actions.
The measurement is mandatory and, if necessary, the tire pressure is brought to normal. If there are too large backlashes or any physical damage to the parts, the specialist must stop the procedure and refuse to make adjustments to the client if it is not possible to fix the problem on the spot.
If, nevertheless, no deviations were found, the car is installed on a horizontal platform, and then loaded in full accordance with the manufacturer's recommendations. In other words, if the angle values for a specific load were indicated at the factory, then it would be a direct violation to try to regulate them on a completely empty machine. To install the suspension parts in the working position, they first squeeze it with effort, pressing the back and front of the car. In order to avoid serious errors in the measurement process, preliminary compensation of the runout of the disks is carried out, regardless of which stand is being adjusted. To carry out this procedure, the axle is hung by the master, measuring instruments 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 by 20-30 cm.
How is the adjustment done?
Since all installation angles are interconnected, when they are adjusted, professionals try to follow an extremely clear sequence. First, the castor is adjusted, and then the camber and toe are changed. In the overwhelming majority of modern foreign cars, only the last parameter is set up.
Castor adjustment involves changing the number of washers, while the wheels of the car are braked by the working brake system (but not by the handbrake) - for this, the workshops use a specialized pedal lock. In principle, the procedure for adjusting the castor is one of the most time-consuming for "breakers", it takes a lot of time, and therefore many do not like it. Some experts can even cut the pucks with a chisel, while others simply do not focus on the castor or try to convince their clients that this corner is in order, so you should always be vigilant.
The camber adjustment on double wishbones is carried out in exactly the same way as in the case of the castor. On a McPherson-type suspension, in most cases, the camber is changed by rotating a special eccentric bolt, with which the rack is fixed to the steering knuckle, but other options can be used. For example, on some models, instead of such a bolt, a special slide mechanism is installed or the adjustment element can be located at the base of the lever. There are also such designs in which the camber is adjusted by moving the ball joint.
Before adjusting the toe, the specialist must first put the steering rack in the middle position , with the steering wheel standing up straight and securing it using a special lock. Adjustment is carried out by rotating the adjusting clutch of the tips on each side (in no case on one side). One of the signs of a correctly conducted operation is the direct position of the steering wheel without any distortions in the process of rectilinear movement. At least on this basis, you can always determine how well the adjustment was carried out and whether it really helped you cope with problems during the ride.