Premature tread wear
A tire is one of the most important elements that influences traffic safety and the service life of the entire vehicle. A tire is quite an expensive thing, and its price is a convincing argument expressing the complexity of the design and the conditions in which the tire has to work. Everyone who drives a car should remember that the tire experiences heavy loads during movement, which increase during acceleration, braking and turns. In order for a car to move at a speed of 100 km/h, the wheels must rotate at over 900 rpm. How difficult it is for a tire can be estimated by remembering that only a small part of the tire, i.e. its contact patch with the road, takes on all the loads.
These are the so-called objective, natural conditions of tire operation. However, there are also subjective reasons that affect their service life. These are: driving style, cruising speed, frequency of brake use, wheel alignment angles, tire balancing and pressure.
To use tires wisely and economically, you need at least a minimum of information about them.
Depending on the vehicle's purpose and operating conditions, tires with four types of tread patterns are used (Fig. 63): road, all-purpose, winter, and high-cross-country.
It is not easy for a car enthusiast when he has to drive a city car to places where the asphalt ends, or to drive in winter. It is no better for the car owner VAZ-2121 "Niva", if it mainly drives on city highways. A good option is to have two sets of tires, but not everyone can afford it. When buying a new set of tires, it is necessary to analyze the conditions of the upcoming operation, weigh all the pros and cons, and also study the capabilities and features of each type of tire-
Tyre makers strive to design a tread in each new model that would have: increased wear resistance, reliable grip on the road surface; improved shock-absorbing properties that could weaken the impacts and shocks transmitted to the tire carcass, protect the tube and carcass from mechanical damage, and reduce vibrations transmitted to the transmission.
The name of the tread pattern itself is a kind of tire passport. To have something to compare with, we will take as a starting point a tire with a tread that has a road pattern (see fig. 63, a). The main advantage of this type of pattern is a very dense cluster of elements separated by narrow grooves and furrows. Such density provides the tire with reliable grip on any hard dry or wet surface. A serious disadvantage of these tires is their unsuitability for driving on dirty and snowy roads. Mud and snow instantly fill the narrow grooves, and the tire turns into a smooth skating rink.
For driving on flat dirt roads, tires with a universal pattern are most suitable (fig. 63, b). The tread elements are not tightly arranged. Sufficiently wide transverse and longitudinal grooves allow dirt that has accumulated in them to be removed without much difficulty. It should be remembered that a loose pattern reduces the contact area, and therefore increases specific loads. This leads to increased wear of tires with a universal tread pattern by 10-15% when driving on asphalt compared to tires with a road pattern.
Considering that most modern passenger cars are all-weather, there is a need for wide-profile tires (in a figurative sense), capable of replacing tires with road and universal patterns in inclement, snowy weather. To provide such a compromise solution, the tread of tires with a winter pattern (fig. 63, in) it is made up of separately located blocks, the area of which is 30-35% smaller than the area of contact between the tires and the road surface.
Even such relative universality of tires with a winter tread pattern does not exclude increased wear of these tires when used on hard-surface roads compared to tires with a road pattern. This is especially noticeable with increasing air temperature. Tires produce increased noise and, most importantly, fuel consumption increases.
The best option for using winter tires is to use them in winter with studs. Use tires with increased cross-country ability (see fig. 63, g) it is only advisable to use them for their intended purpose. They are not suitable for driving on hard-surface roads, either from an economic or traffic safety point of view. The tires wear out very quickly, and you have to drive twice as slowly as on tires with a road tread pattern. Constant vibrations have a negative effect on the general condition of the car and its components. The tires create increased noise and cause significant fuel consumption.
In order to freely understand the data indicated on the sides of tires of different models, you need to know what information each letter and number, cast or applied to the tire, carries. First, the tire size is indicated, and then all the other data: model; "Steel" marking for tires with a steel belt and "Radial" marking for radial tires; maximum permissible speed of movement; "M-S" sign on tires with winter tread pattern; load index; "Tubeless" inscription on tubeless tires; direction of rotation with a strictly directional tread pattern. In addition to the listed data, the tire can be marked with the letter E — the certification mark in accordance with the Rules of the UN Economic Commission for Europe (ECE). And that's not all. A group of numbers and letters applied without any intervals, for example, 114Y200133, will tell you that the tire No.200133 was made in Yaroslavl in the 11th week of 1984.
Each new tire model is naturally more advanced than its predecessor. The well-proven MI-166 tire has been replaced by the universal IN-251 tire from the Bobruisk Association, designed for cars VAZ-2105 and VAZ-2107, and therefore for all other VAZs. This is the first domestic model in which the ratio of the tire profile height to its width is 70%. The marking of this tire is: 175/70 13. Official tests have confirmed that the mileage of IN-251 tires is within 56-58 thousand km, which is 25% higher than the mileage of MI-166 tires. In addition, fuel consumption when installing these tires is reduced by 2%.
Considering that radial tires are the most widely used, let us dwell in more detail on the issues of operating such tires. The radial design is, first of all, highly flexible sidewalls. Due to this quality of the sidewalls, the contact patch of the tire with the road increases, which ensures good grip on the surface and increased stability of the car when driving. However, radial tires have one very vulnerable spot - the same sidewalls. When the wheel hits, the weakest spot - the sidewall - is destroyed. Therefore, driving on radial tires on stones and potholes is an unwise activity. To overcome such areas, you need to reduce the speed to a minimum and be especially careful.
When using radial tires, you need to learn to approach sidewalks carefully, remembering that even on a good asphalt city road you can damage a tire in an instant by unsuccessfully hitting a curbstone.
It has long been known that low tire pressure is one of the reasons for premature tread wear. On diagonal tires, the pressure drop is immediately noticeable. Radial tires often mislead motorists. The fact is that, thanks to the elastic frame, a tire inflated to the norm seems to be deflated. This phenomenon lulls motorists' vigilance, since a decrease in pressure from 0.19 to 0.12 MPa is practically not noticeable to the eye, and at this time the tires wear out intensively. Do not be lazy, when leaving, check the tire pressure once again. The attention paid to them pays off a hundredfold.
And the last thing. There are cases when, for unknown reasons, it is not possible to fix a puncture in the tube on your own. The secret is that radial tires are often equipped with tubes made of butyl rubber. Such rubber is used to minimize air penetration through the walls of the tube, and therefore eliminate the need for periodic inflation of the tires. Repair of a butyl rubber tube must be done with raw butyl rubber. Different materials are incompatible. Distinguishing features of these tubes are a yellow BK stamp or a yellow stripe applied to the side facing the wheel disk.
In order for the tread to wear naturally, without accelerating causes, you should know for sure what the main factors affect wear are. These are primarily: wheel alignment angles, imbalance and air pressure in the tires.
Wheels of VAZ cars require a comprehensive and precise check. This can be done qualitatively only on stands that are subject to regular calibration. If the wear is uniform and does not cause concern, there is no point in driving the car for a check. If the need to check the wheel alignment angles has arisen (an accidental wheel impact, driving on a bumpy road, etc.), it is advisable to carry out an express check, as they say, "on the fly". For this purpose, it is advisable to have simple devices with which you can check the wheel alignment at any time.
The toe-in is usually checked with traditional sliding rulers. They are available for sale, and making them yourself is not particularly difficult. To check the wheel alignment at home, it is more convenient and accurate to use levels. A simple design of such a device (Fig. 64) was suggested by one of the car enthusiasts.
A rotary bar 4 is attached to the base 3, and a level 6, installed in frame 5, is attached to it. A scale 2 with a division value of 1 mm is also fixed to it. The main condition in manufacturing the device is to ensure a distance of 142 mm from the axis of bolt 7, which secures the device, to the edge of the scale. If this size is observed, moving the scale by one division (1 mm) will correspond to turning the bar by an angle of 24'.
To check the wheel alignment angles, a horizontal, level surface is required. The check sequence is as follows:
- set the car wheels to the straight-ahead position;
- ensure the tire pressure is adjusted according to the instructions, taking into account the type of tires;
- press the front of the car from top to bottom several times to ensure the suspension parts are in the correct position;
- secure the device using the wheel mounting bolt, which is currently in the upper position I;
- by turning the bar 4 up or down, set the air bubble to the middle of the level and note its position relative to the mark on the base;
- move the vehicle forward or backward to position II, when the device is at the bottom;
- re-install the bubble level to the middle and determine how much the scale has shifted relative to the first position. This value, divided by 2 and converted to degrees (remember, 1 mm equals 24') will give the camber angle. Do the same with the other wheel.
The camber is considered positive if, in the second case, the bar with the level has to be turned upward to set the bubble to the middle position.
The camber angles are adjusted by removing or installing additional washers between the lever axis and the cross member. To increase the angle, remove the same number of washers from both bolts. To decrease it, add more. The adjusting washers have part of the (slightly larger than the diameter of the bolt), therefore, when removing or installing washers, it is only necessary to unscrew the bolts a few turns.
Unbalanced, unbalanced tires cause a lot of trouble. Firstly, imbalance is a violation of the wheel mass, which leads to its intensive wear. Secondly, imbalance causes vibration of the car in certain driving modes, and thirdly, the stability and controllability of the car worsen. Wheel imbalance can consist of imbalance of the tire, disk, uneven density of the tube and tire material and a number of other factors.
To eliminate imbalance, wheels are subjected to static and dynamic balancing, i.e. processes that first determine the magnitude and direction of unbalanced forces and then eliminate them. The most advanced balancing method is dynamic, but it requires fairly complex equipment, so dynamic balancing must be performed at a station.
However, operating experience confirms the opinion that when driving at speeds not exceeding 90 km/h, static balancing alone is sufficient.
Static imbalance is, simply put, the presence of a heavy spot in the wheel. When the car is moving and the wheel speed increases, this heavy spot creates sharp impacts of the tire on the road. There is no need to comment on the results of such impacts.
To statically balance a wheel, proceed as follows:
- a wheel mounted on a device simulating an axle is mounted on two prisms;
- having provided the wheel with rotation, they give it the opportunity to stop on its own. The presence of a heavy spot will make the wheel stop in a position where the heavy spot is at the bottom. Having repeated the experiment several times, they are convinced of the stable position of the heavy spot;
- after the wheel stops, a weight is placed on the top of the rim and the wheel is spun again. When the weight of the weight is chosen correctly, the wheel will stop in different positions.
To ensure the most uniform placement of weights at home, you need to remember that:
- if the weight of the weight does not exceed 80 g, it is divided in half and each half is installed on the inner and outer edges of the rim, respectively;
- if the weight of the sinker exceeds 120 g, then most of it (80 g) is installed on the inner edge.
Vehicle deviation from straight-line motion
The appearance of this defect should alert the driver, as the car loses its maneuverability, resists the driver, and all together affects traffic safety.
What causes a car to pull away? There are several reasons. The most common ones are: different air pressure in the left and right tires; front wheel alignment angles incorrect; deformation (as a result of the blow) suspension arms; incomplete release of one of the wheels; loss of elasticity of one of the front suspension springs; displacement of the rear axle from the vehicle axis due to deformation of the rear suspension rods.
Check the tire pressure after they have cooled down to the ambient temperature. The right and left tires should have the same pressure.
The correctness of the front wheel alignment angles must be regularly checked on special stands, which are available at every service station. When the alignment angles cannot be adjusted, the "culprit" is deformed front suspension arms. The lower arms are most often deformed. If you find a deformed arm, it must be replaced.
[The text is copied from the online portal: VazBook.ru]
Incomplete release of one of the wheels can be determined by touch. The disk of the suspected wheel should be hot. If this is indeed the case, it is necessary to find out the reason for the braking, i.e. disassemble the wheel cylinder and eliminate the defect.
If one of the springs has lost its former strength, it will immediately give itself away - it will compress more than its partner and skew the car. Replacing the spring, the front suspension arm and eliminating such faults as the displacement of the rear axle, violation of the installation angles of the front wheels, must be done at a service station, since in these cases you cannot do without special devices and stands.