Car suspension and chassis maintenance. Chassis maintenance

Chassis maintenance. Malfunctions of the chassis elements (frames, axle suspensions and wheels) mainly occur when operating vehicles with a load exceeding the maximum load capacity, as well as when operating in difficult conditions on unprofiled roads. The main malfunctions of the front axle include the deflection of the front axle beam, the wear of the pivots and pivot bushings, the development of seats for the wheel bearing cages, the violation of their installation angles, resulting in poor vehicle handling and increased tire wear. Broken springs or sagging of suspension springs, as well as failure of shock absorbers, ultimately cause increased tire wear. The malfunction of the units and components of the chassis is partially detected by inspection during the EO. The scope of work of TO-1 includes checking the condition and fastening of the front and rear suspensions and shock absorbers, measuring the play in the wheel bearings and pivot pins, as well as assessing the condition of the frame and front axle beam. According to the schedule, in accordance with the lubrication map, the pivot bearings or pivot pin bearings are lubricated. Check the condition of the tires and the air pressure in them, which, if necessary, is brought to normal.

During TO-2, in addition to the above works, they check and, if necessary, adjust the correct installation of the front and rear axles, the installation angles of the front wheels, fix the clamps, ladders and pins of the front and rear springs, spring cushions and shock absorbers, set the minimum clearances in the wheel bearings. Inspection of the frame allows you to establish changes in its geometric shape and dimensions, the presence of cracks, the curvature of the side members and cross members, the condition of the fastenings to the frame of the brackets of the springs, springs and shock absorbers.

Checking the geometric shape of the frame can be done by measuring the width of the frame in front and behind along the outer planes of the side members.

The difference in width should be no more than 4 mm for GAZ vehicles. The longitudinal displacement of the frame spars from their original position can be determined by measuring the diagonals between the frame cross members in its individual sections.

The length of the diagonals in each section must be the same. A minimum deviation of no more than 5 mm is allowed. The condition of the suspensions is checked during maintenance by external inspection, and their fastening is checked by applying force.

When inspecting the springs, broken or cracked sheets are revealed. The spring must not show visible longitudinal displacement, which may occur due to shearing of the central bolt. When checking the reliability of the fastening of the springs, it is necessary to turn Special attention on the degree of tightening of the nuts of the step-ladders and the absence of wear on the bushings of the hinged springs. If the springs are attached to the ends in rubber cushions, pay attention to their integrity, as well as to the correct position in the support. The nuts for fastening the ladders and clamps of the springs are tightened evenly, first the front ones (along the direction of the car), and then the rear ones.

Maintenance of shock absorbers consists in checking their fastenings, timely replacement of worn rubber bushings. Particular attention is paid to tightness control. If the shock absorber has liquid streaks on the surface and has lost its shock-absorbing properties, it is repaired, tested after repair and installed on the car. Wheel failures are the result of improper use.

These include the development of holes for studs or fastening nuts, cracks in the wheel disks, damage and curvature of the flanges and rims, bead and lock rings, wheel runout as a result of inept mounting of the tire on the rim, wheel imbalance, corrosion and violation of the paintwork of the wheel rim. These faults are detected during an external examination, and the runout is checked by rotating the suspended wheel. Tires with minor tire damage or tube punctures are repaired under ATP conditions. For this purpose, electric vulcanizers and raw rubber patches are used.

Tires with a worn out tread, but a suitable carcass, are handed over to a tire repair company for restoration of the projector. For uniform wear of the tire tread, it is recommended to periodically rearrange the wheels from the rear to the front axle after 6-8 thousand km according to the rearrangement scheme, including the spare wheel. When rearranging the wheels, the tread pattern (if it is directional) should be taken into account, which is indicated by an arrow on the sidewall of the tire.

When the wheel is correctly installed, the arrow and the predominant direction of rotation when moving forward must match. Tire mounting is carried out only on a serviceable rim. Before mounting, always check the condition of the rim. It must have a regular round shape, the edges and landing shelves must also not have damage, nicks and bends, paintwork violations. Dismantling and installation of tires of passenger cars is carried out on a stationary stand Sh-501M. It consists of a support disk (table) with a wire from a reversible electric motor, a pneumatic pressure device, a dismantling lever stand and an equipment cabinet.

The working bodies of the stand are the support table, where the wheel is attached, two levers driven by a pneumatic cylinder and swinging in a vertical plane on a common axis. The end of each lever is equipped with a horizontal disk that serves to press the tire bead from the rim. The levers move in a vertical plane by the force of a pneumatic cylinder, the air supply to which is carried out by a pedal that simultaneously controls the switching on of the electric motor.

After assembly, the wheels of cars and trucks must be balanced. Wheel balancing is carried out to eliminate their imbalance (imbalance), which is a consequence of the uneven distribution of the mass of the wheel relative to the axis or the vertical plane of symmetry. Imbalance in the rotation of the wheel causes it to beat and uneven increased tire wear. To reduce the influence of unbalance, the wheels are subjected to static and dynamic balancing.

Static balancing can be done directly on the vehicle at the front wheel hub. To do this, hang the wheel, loosen the tightening and attach the wheel to be checked to it. The wheel is brought into rotation clockwise and allowed to stop on its own, marking with chalk on the sidewall of the tire the upper stop position on the vertical passing through the axis of rotation.

Repeat the same when rotating counterclockwise, marking with chalk after stopping the second upper mark. The distance between the two marks is divided in half and a new middle mark is marked, which will indicate the heaviest place on the wheel, located diametrically opposite the received mark. To balance the heavier part of the wheel, near the middle mark, on both sides of it at a distance of about half the radius of the rim, balance weights of equal mass are hung on the edge of the rim and again give impetus to the rotation of the wheel, watching where it stops.

If the wheel stops in a position in which the weights are below the axis of rotation, then their mass is sufficient to balance the wheel. Otherwise, weights of a larger mass are selected. After selecting the weights, successively pushing them apart from the middle mark and checking by rotation, they find the position of indifferent equilibrium, i.e. the ability to stop after the rotation stops in any position. 1.2.2.

End of work -

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Chassis of the car

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Crawler includes assembly units, which are bogies and caterpillar chains.

Chassis of machines operate in conditions of high pollution and significant shock loads. This causes intense wear and destruction of their components.

The main causes of failures and malfunctions of caterpillar trucks are due to wear and damage to track and support rollers, tension wheels, and elements of delivery mechanisms. Track chains fail due to wear, breakage, cracks in links, shoes, pins and bushings.

Faulty track units make it difficult to drive machines.

With significant wear of the caterpillar chains, there is a possibility of their jumping off when the machines turn due to a mismatch between the steps of the caterpillar links and the teeth of the drive wheels, and the loads on the assembly units of the bogie and transmission increase.

Track tension has a significant impact on the wear rate of propulsors, power and fuel efficiency of machines. If they are incorrectly tensioned, the power consumption of engines for the movement of machines increases by 7 ... 9%.

To eliminate jerks when turning on and reversing the stroke, as well as jumping off the caterpillar chains when the machines are moving, especially on turns, their tension is required to be adjusted. However, with excessive tension, the values ​​​​of traction indicators decrease, there is increased wear of bearings, articulated joints and other parts of the chassis.

Maintenance caterpillar track includes the following work.

Daily maintenance and TO-1 of the undercarriage of tracked vehicles consists in carrying out harvesting operations, monitoring the condition of track links and bogie components.

At TO-2 and TO-3, the tension of the caterpillar chains, radial clearances in the bearings of idler wheels and road wheels, axial clearances in the bearings of the supporting rollers and suspension carriages, fixing, adjustment and lubrication operations are checked.

The degree of wear and the pitch of the caterpillar links are determined by a special template according to the total length of several links in the tensioned state.

How the tension is controlled depends on the track design. So, for a multi-support frame caterpillar installed on excavators and tractors, the tension is checked by measuring the height of the lift above the rear support roller or chain slack in the area between the axles of the support rollers. The values ​​of the measured distances, which are in the range of 30 ... 50 mm, indicate the correct tension of the caterpillar chains.

For frameless tracks, the tension is determined from the bar applied to the bottom edges of the supporting rollers to the tracks. The distance should be 130...150 mm.

Increasing and easing the tension of the track chains is done by moving the wheels with the help of tensioner screws, adding or removing excess lubricant from the hydraulic tensioner, and in other ways, depending on the designs of the machines.

To evenly distribute the tension of the track chains, the machines move back and forth. Then the tensioners are re-checked and fastened.

If, after several adjustments, the idler wheel is in its most forward position, the track chain is disengaged to remove the link.

At current repair running gear failures are often eliminated by replacing parts directly on the machines. If deviations from the standard stroke parameters are not eliminated by adjustment, the mechanisms are disassembled.

Some parts with one-sided wear are rearranged or turned over. For example, as the rims of the road wheels wear out, the suspension carriages are rearranged in places in a cross pattern, and when the teeth are worn up to 4 mm, the drive wheels are removed and installed on the other side of the bogies.

The guide wheels are dismantled when the bushings of the supports and the surfaces of the crank axles mating with them are worn out, and the threads of the fixing bolts are broken. When the wheel rims are worn, they are replaced. During assembly, the axial clearance in the bearings is adjusted.

Track rollers wear out along the outer diameter. This distorts their geometric shape and leads to jamming, crushing of protective caps, wear of mounting holes and surfaces for seals. The shapes and dimensions of the rollers are restored by surfacing or pressing steel bandages, followed by welding and processing. If it is impossible to carry out these operations, the rollers are replaced. Damaged seals are also replaced.

The support rollers wear along the rims. As a result, they jam on the axles and the lubricant leaks through the gaps of the sealing rings. Defective rollers are replaced.

The repaired wheels, when assembled, must turn freely on the axles. The axial run must not exceed 2 mm. When installing the wheels, the deviation of the shoulders from a straight line should be no more than 2.5 mm.

In the event of cracks, deformation of springs and rods, the delivery mechanisms are replaced.

For screws of tension mechanisms, no more than two extreme threads are allowed to be torn off.

Suspension carriage failures occur due to wear of trunnion seals, bushings and balancer axles, and track roller bearings.

To remove the complete carriages, the machines are placed on stands and the caterpillar chains are disconnected. Dismantling and assembly of carriages is carried out on special stands. After repair, the free rotation of the carriages on the trunnions of the frames is controlled.

Track chains wear links and pins. To remove the tracks, the fingers are pressed out in areas close to the drive wheels. Removed tracks are reeled onto drums for easy transportation and storage.

Wear and cracks in the soles of the links and partial breakage of the folded edges are repaired by welding. Through cracks are welded with the installation of an overlay on the sole, surface cracks are only welded.

Worn pins and bushings can be flipped 180° and run on the non-worn side or replaced.

When assembling caterpillar chains, their straightness and reliability of link fastening are controlled.

Chassis and suspension of wheeled vehicles wear out during operation, and their elements (springs, leaf springs, wheel hubs and discs, tires) are damaged.

As a result of wear, the control of machines becomes more difficult, the straightness of the course is lost, and difficulties arise when performing certain works (for example, profiling the subgrade).

The causes of hub malfunctions are the wear of the bearing seats, the threads in the holes for the studs of the axle flanges and wheel rims, as well as cracks.

Violation of disc performance occurs due to bending of the attachment plane, rims and edges, cracks, wear of holes for wheel studs.

Leaf springs are repaired due to wear in thickness, fractures, cracks, bending, loss of elasticity, shift of sheets (gaps between them), breakage and shift of clamps, shear and breaks of central bolts.

Cylindrical helical springs are subject to kinks and settling (height reduction).

The undercarriage largely determines the safety of machines, and improper operation can lead to accidents. Therefore, it is necessary to timely control the technical condition of the assembly units of the chassis, their maintenance and repair.

Maintenance chassis and suspension of wheeled vehicles consists in carrying out the following work.

Every shift maintenance and TO-1 running gear consists of cleaning, external inspection, checking the wheel fasteners; springs.

At TO-2, the braking distance is controlled, lubrication operations are carried out in accordance with the instructions of the manufacturers.

At TO-3, it is provided to control the installation parameters of the front wheels and axial clearances in the hub bearings.

The wheel alignment control ensures the normal operation of the front axles, improves the controllability of the machines, reduces fuel consumption, and eliminates accelerated tire wear.

Checking the installation of the wheels consists in determining the angles of their convergence (convergence) (Fig. 5.11) and camber, as well as the transverse and longitudinal inclinations of the pivot pins of the front axles.

Toe-in is characterized by the difference in the distances between the middles of the wheels in the front and rear parts. The convergence value is set by the manufacturers and, for example, for the DZ-122 motor grader is 5...8 mm.

Camber, determined by the center distance of the fork holes, should be +3 mm. The angle of convergence of the wheels is regulated by the rotation of the transverse link, the camber - by turning the forks.

To adjust the front bearings, the wheels of the machine are hung out, the hub caps are removed, the lock washers are released, the adjusting nuts are screwed in until the play in the bearings is eliminated, and then unscrewed by 1/6 of a turn. In this case, the wheel should rotate freely, with some braking. Assembly is carried out in reverse order.

When adjusting the rear wheel bearings, after removing the covers, the axle shafts are removed, the lock nuts are unscrewed, washers and lock rings are removed. The fully screwed adjusting nuts are released 1/12 of a turn. Then the removed parts are installed.

Maintenance may include the following.

When repairing the chassis of wheeled vehicles, the seals and bearings of the front wheel hubs and other parts are replaced.

Hubs with cracks, worn bearing seats over 0.05 mm are replaced. Breakage or wear of the thread in the bolt holes of the axle flanges is eliminated by threading repair dimensions.

Disc cracks that do not come out of the hub holes and do not pass through the entire disc or rim are welded. If there are other cracks, the discs are replaced. The bends of the mounting planes, rims and edges are eliminated by editing.

Repair of springs consists in disassembly, replacement of defective parts, assembly, control operations. Dismantling and assembly work is carried out on stands or screw fixtures.

Before assembly, the leaf springs are lubricated with graphite grease. When assembling, the sheets should fit snugly against each other and the clamps. A probe 0.5 mm thick and 20 mm wide should not pass between the sheets at the clamps. In the middle part of the springs, the permissible clearance without load is 1 mm. It is not allowed to shift the sheets relative to the clamps by more than 5 mm.

Tire service

The technical operation of tires has a significant impact on the safety and economy of machine operation.

A pneumatic tube tire includes a tire, a tube and a rim tape, a tubeless tire includes only a tire.

Tire elements are carcass, belt, tread, sidewall, bead.

The main causes of tire failures and malfunctions include wear, chipping, tread peeling, tread and sidewall cuts, through damage, rupture and fracture of the carcass, beads and bead rings.

In most cases, these damages occur due to non-compliance with the established tire operating conditions, the main indicators of which include load, internal pressure, speed, as well as ambient temperature and road surface condition.

Excess load reduces the resource of tires (Fig. 5.12).

During tire operation, the most significant technical parameter that determines the resource is air pressure, the decrease of which causes overload and deformation of the sidewalls, an increase in temperature, fatigue stresses in the carcass, thread breakage, and an increase in tread wear (Fig. 5.13). At the same time, fuel consumption increases by up to 15%.

Tire wear is affected by speed. So, at a speed of 60 km/h, tire wear is 2 times less than at a speed of 100 km/h.

The optimal temperature regime of the tire is 70...75 °C. When heated to 100 °C, the wear resistance of rubber, as well as the bond strength between rubber and cord, decrease by 1.5–2 times. Tire heating is largely determined by the ambient temperature.

The deterioration of the road surface reduces tire life by up to 25% on gravel and gravel roads and up to 50% on rocky and broken roads.

The technical condition of the machines (wheel alignment angles, steering play, oil leakage through the hub seals, incorrect tightening of nuts, lateral wheel runout) has a significant impact on tire wear.

Maintenance allows you to maintain tires in good condition, reduce wear, identify and repair damage.

When EO is performed external examination, foreign objects located between the dual tires and in the treads are removed, the presence of damage and oil products on the tires is checked.

The work carried out during TO-1 includes monitoring the condition of spools, caps, outer surfaces of tires, and air pressure. Pumping is necessary if the pressure deviates by more than 0.01 MPa (0.1 kfs / cm 2) from the norm.

The work carried out during TO-2 includes checking the disks and balancing the wheels. In case of detection of dents, cracks, ovality of holes and other malfunctions of the discs after disassembly of the wheels, the damage is eliminated or the discs are replaced.

When carrying out TO-3, the height of the protectors is determined. Tractor tires are recommended to be replaced or retreaded at 80% tread wear. Untimely replacement of tires leads to an increase in the likelihood of external damage and a significant decrease in traction performance.

Repair Tires can extend their lifespan. Tires are reusable products. Up to 70% of failed tires are completely and partially suitable for restoration.

Tire failures are divided into four groups.

The first and second groups - local damage: through cuts up to 110 x 20 mm in size, tears up to 50 x 40 mm in size, punctures, scratches.

Damages of the first group (small scratches, cuts) initially do not have a significant impact on the performance of tires, but further contribute to their destruction. Tires are delivered to the place of repair without removal from the car. Damage to the second group requires the removal of the wheels.

The repair sequence for tires with local damage includes an inspection from the outside and inner sides using a hand expander, removing stuck foreign objects and dirt, rounding the edges of cuts and tears to prevent their growth. The contours of damage are processed to the full depth, smeared with glue, lined with special rubber, the free space is filled with a rubber compound. Tires are installed on a double-sided heating vulcanizer (Fig. 5.14).

To ensure strength, self-vulcanizing patches are glued to the internal cavities of the tires.

In the process of self-vulcanization, the tire is kept for 1-3 days in a room at a temperature not lower than 18 °C.

The final stage of tire repair is their finishing, which consists in removing rubber deposits, bumps, burrs, and control operations.

When the chambers are accepted for repair, they are filled with air and at a pressure of 0.03 ... 0.05 MPa (0.3 ... 0.5 kgf / cm 2) are immersed in water. Rising air bubbles indicate the location of damage, which is repaired by applying patches of vulcanized or raw rubber. Vulcanization is carried out by electric vulcanizers for 15...20 minutes at a temperature of (150±5) °C. Repaired chambers are tested for leaks in a bath of water.

In road conditions, self-vulcanizing patches are used to repair the chambers. They eliminate gaps up to 100 mm. Curing time is 3...5 minutes. When damaged by round objects with a diameter of up to 10 mm, the tires are repaired with self-vulcanizing rubber inserts. Otherwise, when driving on a wet road, water gets into the damaged area. This can cause corrosion of the steel cord and delamination of the frame.

Tubeless tires are not structurally designed for multiple disassembly-mounting, as in this case the sealing layer of the beads is broken. Therefore, punctures up to 7 mm are eliminated without removing the tires from the rims. With the help of a special awl, rubber bands coated with a self-vulcanizing compound are installed.

The third group of faults includes complete wear of the tread with local damage. Tires with such defects can be restored at specialized repair shops.

Restoration of worn tread is carried out by hot and cold methods. The repair sequence includes washing and drying tires, fault detection, cutting off the old tread and “roughening” the surface.

In hot retreading, an adhesive solution is sprayed onto the roughened surface and an intermediate thin layer of interlayer rubber is applied. The new tread is applied with a single layer of thick, uncorrugated and unvulcanized tape or by winding a tow of unvulcanized rubber.

The main recovery operation is vulcanization - the production of rubber by heating rubber with sulfur. Hot vulcanization is carried out on a vulcanizing machine. Its inner shell is a metal shape with a relief tread pattern that will be imprinted on the tire.

In the cold method, a finished tread is applied to the treated surface, the tire is placed in an elastic shell that compresses the tread and is placed in a special chamber, the pressure and temperature in which do not exceed the standard operating parameters. Thus, the original strength properties of the tires are not violated.

During the final control, static balancing of tires is performed by applying an adhesive solution to the lightest part of the inner cavity of the tire.

The fourth group includes tires with large through damage, carcass delaminations. In these cases, they are discarded and disposed of. Ultrasonic flaw detectors are used to detect internal defects (laminations in the carcass, between the carcass and the tread).

The most responsible technological operations are installation and dismantling. Failure to do so can result in bursting of pressurized tires, rupture of circlips, and reduced safety when operating machines. The dismantling and mounting of tires is carried out mechanized on special stands (Fig. 5.15).

At transportation and storage tires are guided by the requirements of manufacturers.

During storage, tires should not be exposed to moisture, light, heat, lubricants, fuels, acids, alkalis, prolonged contact with copper and corrosive substances, prolonged one-sided loading, kinks, piles on top of each other, and contact with sharply protruding bumps.

Tires are stored upright and rotated periodically every 3 months. It is not recommended to store them in stacks. This leads to loss of shape, collapse of the tire walls and, in operation, contributes to the occurrence of cracks and ruptures.

The chambers are stored in an inflated state in tires or on brackets with a semicircular surface. Every 3 months in order to avoid wrinkling, it is recommended to turn them over on the brackets. Cameras may be stored in packages or on pallets stacked or rolled. When rolled up, the camera can be stored for no more than 3 months.

Rim tapes are stored on brackets or in packs on pallets.

Similar information.

TECHNICAL MAINTENANCE AND CURRENT REPAIR OF THE RUNNING GEAR OF THE VEHICLE.

During the operation of the car, failures of the elements of the chassis occur, the share of which is about 15% of their total number.

As a result of malfunctions, the installation angles of the front wheels change, and accordingly, driving becomes difficult, tire wear increases, fuel consumption increases due to increased rolling resistance of the wheels, and the likelihood of a traffic accident increases.

To maintain the working condition of the running gear of the car, visual running diagnostics are carried out and maintenance and TR work is performed.

They include checking the condition of the tires and creating normal internal air pressure in them; periodic control and adjustment of the angles of installation of the front wheels; checking clearances in wheel hub bearings and pivot joints; checking the condition of the frame and suspension; checking the fastening and lubrication of the running gear parts.

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Possible malfunctions of the chassis of the car and their causes.

High noise level and knocking when driving.

The reasons:

1. Loosening of fasteners of suspension parts (shock absorber strut, shock absorber, anti-roll bar, stretch marks, torque rods, wheel nuts). Eliminated by tightening their fasteners.

2. Wear or destruction of rubber-metal joints, rubber pads, bushings and buffers. Defective parts are replaced.

3. Damage to wheel bearings. Defective parts are replaced.

4. Worn front suspension arm ball joints, strut or shock absorber failure, spring settling, and spring settling or failure. Defective parts are replaced.

Leakage of fluid from the shock absorber or shock absorber, increased swaying of the car body when driving on rough roads.

The reasons:

1. Shock absorber or shock absorber failure.

Roll to knot.

The reasons:

1. Uneven settlement of springs or suspension springs, breakage of spring sheets.

Taking the vehicle out of a straight line.

The reasons:

1. Incorrect adjustment of wheel bearings;

2. Curvature of a beam, rotary levers;

3. Wear of the seat for the kingpin, the kingpins themselves and their bushings, seats for the bearings of the pivot pins;

4. Violation of the installation angles of the wheel

With;

5. Rdestruction of one of the upper supports of the telescopic struts;

6. Hequal elasticity of suspension springs;

7. Rdifferent pressure or different tire wear;

Increased heating of wheel disks.

The reasons:

1. Constrictions or destruction of wheel bearings;

2 . Lack of lubricant (due to leakage through a damaged sealing collar or untimely maintenance);

3. Malfunction of the brake mechanism (when the brake cylinders are jammed);

Vibration of the car while driving.

The reasons:

1. Ddeformation of wheel disks, tires;

2. wheel imbalance;

3. Pdisc curvature;

4. Rupture of steel cord threads of tires. When the steel cord threads of the tires are broken, the vibration is stronger when the car is moving at low speed (wagging of the front or rear of the body).

Running gear diagnostics

Convergence angle wheels most affects the rate of tire wear.

With a positive value of the toe angle on both front tires, one-sided sawtooth wear occurs along the outer tread tracks.

With a negative toe angle, one-sided sawtooth wear occurs along the inner tracks.

Camber angle wheels affects the rate of tire wear. There is a smooth one-sided wear. Significant deviations in the camber angle, typical for cars with a one-piece front beam, require their mandatory correction, otherwise there will be a lot of tire wear.

Pivot angle in the longitudinal plane affects tread wear if it is not equal to the angle of inclination on the other wheel. In this case, one-sided wear of one tire occurs. At the same time, on straight section the road the car pulls to the side. For the angle of inclination of the king pin in the transverse plane (axis of rotation), adjustment is not provided. In a passenger car with linkage suspension, it changes simultaneously with the camber angle.

Steering angle ratio affects front tire wear when the vehicle is not driven in a straight line, such as in big city or on mountain roads. characteristic feature deviations of this parameter is the wear of one extreme track, which is especially noticeable for tires with a road tread pattern.

Rear axle tilt leads to the fact that the car is located at an angle to the trajectory of movement. One-sided sawtooth wear occurs on the rear tires: along the inner tracks of the tire tread on one side of the car and along the outer tracks on the other. If the cause of uneven wear is not eliminated immediately, then after 15-20 thousand km of the car's run, the tread can be worn out in waves over the entire surface.

For trucks and buses, only the toe angle is adjusted, for cars (in most cases) - the camber angles, the longitudinal inclination of the steering axis, the ratio of the steering angles and the toe angles of the wheels (this sequence is required).

Adjustment of the ratio of the angles of rotation is usually achieved by ensuring the equality of the linear values ​​of both steering rods. In order not to change the angle of convergence of the wheels, one rod is shortened, the other is lengthened by the same amount.

The steering angle ratio cannot be a constant value, since this parameter is related to the toe angle. When adjusting, it is necessary to ensure that the angle of non-rotation of the outer (to the center of rotation) wheel relative to the inner wheel turned by 20 ° is equal to the angle of non-rotation of the other wheel when it becomes outer.

Adjusting the toe angle for trucks is carried out by changing the length of the tie rod, for cars with a worm gear - one of the two side rods, for cars with a rack and pinion steering mechanism, it is necessary to adjust the toe angle of each wheel separately from the steering rod. The normative values ​​​​of the angle of installation of the wheels (UUK) are set by the vehicle manufacturer.

When rear-wheel drive vehicles move under the action of road resistance forces, the front wheels diverge, while in front-wheel drive vehicles in traction mode, as a rule, they converge by the size of the existing gaps in the steering linkage. The wheels must be parallel to each other. The standard value of the toe angle does not always provide this condition. The reason is the technical condition of the car, especially with independent front wheel suspension.

The adjustment of the toe angle of the wheels of passenger cars must be carried out when the suspension is loaded, simulating driving conditions: the force on the front axle is 500–600 N, the expansion force on the front wheels is 400–500 N, created by a special load bar when it is installed between the sidewalls of the front tires at the level of the wheel centers . The toe angle is 0 ± 5 "(this position will be taken by the wheels when the car is moving). More precisely, the value of the expanding force is determined by a special nomogram, which takes into account the actual value of the camber angle, the most commonly used vehicle speed and other factors.

Stands for checking and adjusting steered wheels.

The control and installation of the steered wheels of passenger cars is carried out at special posts, on wide-type inspection ditches equipped with a lift for hanging bridges, or on four-column lifts with track-type lifting frames. In any case, they are equipped with appropriate instrumentation and various accessories.

Equipment for measuring wheel alignment when diagnosing the front axle of a car is divided into two groups:

stationary - stands

Portable - appliances.

According to the principle of operation, stands are divided into mechanical, optical, opto-electric and electrical, portable devices - into mechanical, liquid and opto-electric.

The simplest device for measuring the toe-in of the front wheels is a telescopic ruler, which expands under the action of a spring.

When measuring the toe-in of the wheels, the ruler is installed in front of the wheels so that the tips rest against the tires near the edge of the rim, and the ends of the chains touch the floor. Then the scale of the ruler is moved until the zero division is aligned with the fixed pointer and its position is fixed with a screw. The car is rolled forward until the ruler takes a symmetrical position behind the front axle. The amount of movement of the scale relative to the pointer determines the amount of toe-in, which is controlled by changing the length of the tie rod.

On cars with a split front axle (with independent front suspension), the toe-in is adjusted by changing the length of the right and left steering rods by the same amount at the same time, since the asymmetrical trapezoid causes intensive wear of the tire tread even with the correct toe-in value.

The disadvantage of measuring wheel toe with a ruler is its low accuracy due to the small size difference when the car rolls. The accuracy of wheel alignment depends on the accuracy of the ruler scale.

More precisely, this parameter is determined by the angle of convergence of the wheels between the diameters in the horizontal plane. The convergence is considered positive if the distance between the wheels in front is less than in the rear. The angle of convergence is from 5 to 30°. Wheel alignment is only maintained when the vehicle is moving in a straight line. When turning the car, the steered wheels turn at different angles, the angle of rotation of the inner wheel is always greater than the angle of rotation of the outer wheel.

More accurate results are obtained by a ruler equipped with an electric sensor, the readings of which are recorded on the galvanometer scale.

To assess the controllability of the car, you need to know the ratio of the angles of rotation of the wheels. The angle of divergence of the wheels reaches the greatest value at large values ​​of the angles of rotation of the wheels, therefore the ratio of the angles of rotation of the wheels is most often determined when one of the wheels is turned at an angle close to the maximum (20–25 °).

To measure the angles of the wheels, stationary stands are most often used, where the angles of camber, toe-in, longitudinal inclination of the kingpin and the ratio of the angles of rotation of the wheels are measured by the optical method, and the angle of the transverse inclination of the kingpin is measured by level.

Vehicle chassis maintenance.

EO

They inspect the frame and other components and parts of the chassis, check the condition of the springs and shock absorbers.

TO-1

Check the clearances of the steering wheel and levers, wheel bearings, the condition of the pivot connection, fastening and cottering of nuts.

TO-2

Taking into account the scope of work TO-1, the condition of the springs, springs, shock absorbers, front axle beam assemblies, wheel alignment angles, wheel imbalance, condition and fastening of the driveshaft, fasteners are checked.

Checking the technical condition of the suspension.

It is carried out both when signs of its malfunction appear, and for prevention during the next maintenance of the car, since traffic safety depends on the technical condition of the suspension.

Checking the condition of the front suspension consists in examining its elements to detect damage (deformations, cracks, wear), tightening the fastenings of its elements, determining the condition of the ball joints and upper supports of the telescopic shock absorber struts, the settlement of springs, shock absorbers (shock absorber struts) and setting the wheel alignment angles .

With increased heating of the wheel, it is necessary to add lubricant to the hub or replace it, change the worn sealing collar (partial disassembly of the hub), adjust the tightening of the bearings, or replace the failed bearings (complete disassembly of the hub).

Current suspension repair.

consists in checking its technical condition, disassembling, replacing or repairing parts, assembling and adjusting the angles of the front wheels, as a rule, the shock absorber strut or shock absorbers are repaired, and the silent blocks of the suspension arms are repressed.

Changes in the camber and caster angles of the kingpin of a truck can be caused by the deformation of the beam.

If the beam cannot be straightened, it is replaced with a new one.

The inner cavity of the hub after repair and when performing TO-2 is filled with refractory grease.

Adjustment of the rolling bearings of the wheel hubs is carried out with a freely rotating brake drum (there should be no contact between the brake pads).

The front axles are dismantled on special stands or stands.

Pullers are used to press out ball pins, outer and inner rings of rolling bearings; for pressing the pivots - portable hydraulic presses.

The deformation of the front axle beam is determined using various devices, templates, rulers, squares. The beams are straightened under cold pressure.

Worn steering rod joints and kingpin bushings are replaced with new ones: first, one new bushing is pressed in, the second is the base for the reamer shank, which is used to machine a new bushing to the required diameter. When pressing bushings, lubrication holes must be aligned. The treated surface is cleaned of chips, lubricated.

The car every time you travel is under a huge load. It is the chassis that first takes on the blows of our off-road, so it is the most vulnerable element of the car.

Diagnostics and repair of the chassis of the car must be periodically carried out for each car.

It is recommended to carry out suspension every time after 10-15 thousand kilometers, and even more often in the case of off-road operation of the car. Given our "good" roads, running gear repairs have to be done more often than oil changes.

Any car owner understands that safety on the road and only careful attitude depend on the condition of the chassis of the car, timely diagnosis and the car will help increase its performance and driver confidence on the road.

During the diagnosis, a visual and instrumental examination is performed:

1. ball;
2. Silent blocks;
3. Shrusov;
4. steering tips;
5. shock absorbers;
6. toek;
7. shock absorber springs;
8. Wheel alignment;
9. wheel bearings;

Running gear repair

Replacing ball and silent blocks is a regular procedure that is performed on every car. The replacement interval depends on the driving style and the reliability and durability of the assembly. When the silent block is worn, distinct metallic ringing is heard in the suspension when driving through bumps.

The CV joint is used to transmit torque. Its replacement is done in cases where a crunch is heard when turning the steering wheel. At the same time, it is easy to determine which CV joint is to be replaced, just turn to the left - a crunch is heard, which means replacement or repair is necessary and vice versa.

When as a rule, the pads on the axle are changed.

A well-maintained running gear of a car means comfort and safety on the road. After all, it is a complex system, the task of which is to evenly distribute the loads on the supporting parts of the car.

The undercarriage of the car can be hard and soft. The stiffer, the less comfortable the car, but the better the handling. To balance the machine, shock absorbers of the same type are installed.

As already mentioned, the suspension of the car plays a very important role in driving the car, so repairs to the undercarriage of the car that are not done on time can lead to undesirable consequences.

For example, if repairs are not carried out in time, this can lead to consequences, and if you make a sharp turn at high speed, you can even roll over. So, because of such minor faults, it will be necessary to make more significant repairs to the car.

The main causes of suspension failure can be the following: poor quality road surface, poor parts, lack of professionalism among workers performing suspension repairs.

You can determine the malfunction by the following signs: the car starts to divert to the side, the car sways when cornering, vibration, various knocks, uneven tire wear occur during movement.

The car includes restoration of the front and rear suspension. The quality check of the repair work performed is carried out according to a specialized technique using electronic wheel alignment - convergence in a vicious circle.

Encyclopedia of a novice driver Khannikov Alexander Alexandrovich

Running gear maintenance

The technical condition of the car is significantly worsened by various malfunctions and failures of the chassis. So, in the front suspension, bends of the beam, upper and lower levers, wear of the upper and lower ball pins, crackers, liners, rubber bushings are possible. All this leads to a change in the angles of the steered wheels, causing a deterioration in vehicle handling, excessive fuel consumption, and tire wear. Malfunctions of the suspension elements affect the smoothness of the ride, the stability of the car while driving.

The most frequent malfunctions of the running gear are: deviation and partial deviation of the car from the direction of rectilinear movement, the so-called "wobble", in the speed range from 50 to 90 km/h; rocking of the front of the car when driving on rough roads; knocking in the front suspension; a weak knock transmitted to the steering wheel; knocking in the rear suspension; increased wear on the inside of the tire tread; increased wear of the extreme parts of the tire tread; uneven tread wear; sawtooth wear of the tire tread in the transverse direction; one-sided tire tread wear; wheel beating; wheel alignment angles cannot be adjusted; the car tosses from side to side on the road with longitudinal wave bulges and depressions.

The reasons for the deviation of the car from the direction of rectilinear movement are: different angles of longitudinal and transverse inclination of the axes of rotation of the left and right wheels; different camber of the left and right wheels; uneven air pressure in the tires of the left and right wheels; one of the front wheel bearings may be pulled, which leads to an increase in resistance; deformation of the lower and upper arms of the front suspension; violation of the parallelism of the axes of the front and rear axles; braking of one of the wheels of the car on the move due to the lack of a gap between the brake drum and the friction lining; increased imbalance of the front wheels; uneven elasticity of suspension springs.

The reasons for the partial deviation of the car from the direction of rectilinear motion - "wobble" in the speed range from 50 to 90 km / h are: large gaps in the bushings of silent blocks, steering rod joints, in the front wheel bearings; increased clearances between ball pins and liners, pins and bearings; loosening of fastening in the steering; wear of the pendulum arm bushings.

The main reason for the swaying of the front of the car when driving on rough roads is the poor performance of the front shock absorbers.

The causes of knocking in the front suspension are: high wear of the elements of the articulated joints; lack of lubrication in swivel joints; loosening of mounting bolts; sediment, breaks, exfoliation of rubber from the rack support housing; wear of the rubber bushings of the shock absorber antennae; loosening the shock absorber reservoir nut; increased clearance in the wheel bearings; increased wheel imbalance; deformation of the rim or wheel; sediment or breakage of the spring; destruction of compression stroke buffers; malfunction of the suspension struts (for vehicles with front-wheel drive); loosening of the bolts of the brackets of the stretch marks or the bolts that secure the bar of the anti-roll bar to the body; wear of rubber pads stretch marks or rods (for cars with front-wheel drive); loosening of the upper support of the suspension strut to the body (for vehicles with front-wheel drive).

The causes of a weak knock transmitted to the steering wheel may be the deformation of the front wheel discs and a large imbalance of one or two front wheels.

The reason for knocking in the rear suspension lies in the overload of the rear axle; wear of shock absorber bushings; weakening of attachment points.

Wear on the inside of the tire tread can occur due to excess air pressure in the tire;

increased wear of the extreme parts of the tire tread - due to insufficient tire pressure; uneven wear - due to large gaps in the swivel joints of the steering gear and front suspension, malfunction and shock absorbers, large residual unbalance of the wheels; sawtooth wear of the tire tread in the transverse direction - due to improper wheel alignment, and the cause of one-sided wear of the tire tread is the deviation of the camber angle from the nominal value. The main cause of wheel wobble is imbalance.

The reasons for the impossibility of adjusting the angles of the wheels are: deformation of the axis of the lower arm; deformation of the suspension cross member in the area of ​​the front bolts of the lower arm axles; deformation of the steering knuckle, suspension arms or elements of the front of the body; wear of rubber-metal hinges.

The consequence of throwing the car from side to side on the road, which has longitudinal bulges and depressions, is: wear of the bushings or loose tightening of the nuts of the pendulum arm axis; large backlash in the steering trapezium swivel joints and front wheel bearings.

When servicing the technical condition of the chassis of the car, element by element check the tightness of the bearings, the backlash of the front suspension and steering. To do this, with the help of a lift or a jack, the wheel is hung out, taken by the edges from above and below and swayed along the vertical axis, reducing the bearing play. The backlash value should be close to zero. After determining the vertical play, the wheel is taken by the edges in its upper part located in the horizontal plane, applying variable efforts, the play is reduced before the steering wheel starts to rotate. The amount of play along the vertical characterizes the bearing preload, and with a greater force applied to the wheel, shows the wear of the upper and lower hinge joints, horizontally in the middle part of the wheel - the degree of bearing preload, with an increased force applied to the wheel, shows the wear of the steering joints .

Wheel braking is also used to determine the cause of the front wheel play. If play is felt at the same time, then it is the cause of steering wear.

For the rear wheels, the vertical and horizontal backlashes are approximately the same, and a change in their values ​​characterizes the degree of bearing wear. If the front wheel has no vertical play, it is necessary to give the wheel rotation and, by the time it stops, determine the resistance that occurs when scrolling. When quick stop wheels should loosen the bearing preload.

Checks on the amount and nature of tire wear, skidding of the car while driving, noise and knocking, vibration, and heating make it possible to judge the technical condition of the vehicle's running gear.

During each maintenance check the condition of the protective covers of the ball joints of the suspension, paying particular attention to mechanical damage; it is necessary to find out if there are any cracks on the suspension parts or traces of rubbing against road obstacles, deformation of the steering knuckle, lower arm axle, suspension arms and body front elements, and also check the clearance in the upper ball joint and the condition of the lower ball joint. The deformation of the lower arm is determined by inspection.

Analysis of the state of rubber-metal joints has its own sequence. If there is no deformation of the suspension arms and the axis of the lower arm, hang the front wheels of the car; visually determine the radial displacement of the outer sleeve relative to the inner sleeve and appearance hinge. In case of swelling, ruptures and cracking, the hinge is replaced. Rubber-metal joints are also replaced if it is impossible to adjust the camber when all the washers are removed from under the axis of the lower arm.

For vehicles with rear-wheel drive, to check the wear of the upper ball joint of the front wheel suspension, it is necessary to unload the wheel, for which a stop is placed under the lower ball joint. The wear of the upper hinge is determined by rocking the wheel in a vertical plane, while the clearance in the hinge should not exceed 0.8 mm.

On front-wheel drive vehicles, the condition (draft) of the upper support of the suspension strut is checked as follows: a car with a static load of 320, evenly distributed over the body, is installed on a flat area; turning the steering wheel, set approximately the same gap between the compression stroke limiter and the rubber part around the entire circumference; this gap is measured with a template or caliper. It should not exceed 10 mm. If the gap is larger, remove the rack, check the condition of its parts and replace the defective parts.

When servicing and checking the condition of suspension parts removed from the vehicle, it is necessary to carefully inspect and make sure that the suspension arms, cross member, steering knuckles and springs are not deformed or cracked. If any, replace the parts.

When checking the technical condition of ball joints, first of all, you need to make sure that the hinge covers are intact. Breaks, cracks, delamination of rubber from metal fittings, traces of lubricant leakage are unacceptable. Then it is necessary to check if there is any wear on the working surfaces of the ball joints by manually turning the ball pin. Free, without resistance, the course of the finger and its jamming are unacceptable.

The stabilizer bar is checked for deformation and flatness. With a slight deformation, the bar is straightened, with a significant one, it is replaced.

Check the safety of the pillows in the mounting brackets to the body and to the lower suspension arms and replace them if worn.

When servicing the telescopic rack, all parts are checked and dried. They must meet the following requirements: the working surfaces of the piston, piston ring, guide sleeve, rod, cylinder, recoil buffer and valve parts must be free of scoring, dents and wear marks; the disks of the compression and recoil valves, as well as the bypass valve plate, must not be deformed; non-flatness of the bypass valve plate is allowed no more than 0.05 mm (check with a probe on the plate); the working edges of the stuffing box must be free of damage and wear; risks, scuffing and delamination of the fluoroplastic layer on the rod guide sleeve are not allowed; the springs of the recoil and compression valves, as well as the recoil buffer, must be intact and sufficiently elastic; the inner surface of the rack housing must be clean, without scratches and damage, the threads must be in good condition; the tightness of the rack housing is checked with air under pressure; the strut body, bracket, spring cup, swing arm, compression stroke buffer and protective cover must not be damaged or deformed. It is impossible to carry out welding work on the rack, as this may affect the change in the angles of the wheels and the performance of the rack itself.

Carefully inspect the suspension springs. If cracks or deformation of the coils are found, the spring is replaced. To check the settlement of the spring, it is compressed three times until the coils touch. Then a load of 325 is applied to it. The spring is compressed along its axis. The support surfaces must match the support cup surfaces on the telescopic pole.

Check the condition and flatness of the stabilizer bar. If the deformation is insignificant, the bar is straightened, with a significant deformation it is replaced. Pay attention to the condition and safety of the pillows in the boom brackets; if the pads are worn or damaged, they are replaced. If the fingers do not go into the holes of the rack, it is replaced.

Analyze the characteristics of the upper support of the telescopic rack. Rubber delamination, gusts, cracks and large settlement of the support are unacceptable.

When performing maintenance of the chassis, every day before leaving, it is necessary to monitor the condition of the wheels and tires: are there any damages, foreign objects stuck in the tire tread, are there any caps on the valves. In addition, check the pressure in the tires. After every 1000 km of run, the air pressure should be checked with a tire pressure gauge and, if necessary, brought to normal. After the first 2 thousand kilometers, and then every 10–20 thousand kilometers, as well as after strong impacts on obstacles on the road (getting into pits, hitting stones, etc.), you should check the condition of the front suspension parts by inspecting the car from below after installing it on a lift or viewing hole.

It should be checked for cracks on the suspension parts or traces of rubbing against road obstacles, deformation of the levers, stretch marks, stabilizer bar, its struts and body front elements at the points of attachment of the suspension units and parts. Deformation of suspension parts, primarily braces, torque rods, and parts of the front end of the body, violates the angles of the wheels and can lead to the impossibility of their adjustment. If such problems are found, it is necessary to check the wheel alignment angles.

If the car has tires with a diagonal cord, then every 10 thousand kilometers, to improve the uniformity of tire wear and their service life, the wheels should be rearranged. If the car has tires with a radial cord, the rearrangement is carried out only if increased and uneven wear of the tires of the front wheels is detected as a result of a violation of the wheel alignment angles. In this case, check the wheel alignment and swap the rear and front tires, keeping the direction of their rotation, the front tire is swapped with the rear tire on the same side of the car.

Every 10-15 thousand kilometers, you should check the wheel balance, the condition of the suspension ball joints, check the clearances in the front wheel hubs and, if necessary, add grease to them, and every 20-30 thousand kilometers, replace the grease with disassembly of the hubs and flushing details. After 30 thousand kilometers, it is necessary to check the condition of the anti-roll bar.