Reasons for abnormal wear of truck tires and four-wheel alignment

Definition of four-wheel alignment

When performing a truck four-wheel alignment, you need to follow the following steps: Drive the vehicle to the alignment lift, and the front wheels need to be parked in the center of the loading tray for pre-alignment testing, including tire pressure, suspension, and chassis testing. Then perform data detection, install sensors on the four wheels, fix the steering wheel and brake pedal, lift the vehicle, and set the parameters for testing. Finally, based on the data, adjust the four-wheel alignment data of each tire according to the degree of deviation.

Common abnormal wear and tear include the following:

Tire wear is mainly caused by the friction between the tire and the ground. The driving conditions of the car, such as starting, turning and braking, are constantly changing. If the turning speed is too fast, the starting is too hasty, and the braking is too strong, the tire will wear quickly. If the tire is used improperly or the front wheel is not aligned correctly, it will cause abnormal wear. Common abnormal wear includes the following:

1. Early wear of the central part (crown) of the tire: The main reason is excessive inflation. Properly increasing the inflation of the tire can reduce the rolling resistance of the tire and save fuel. However, when the inflation is too large, it will not only affect the vibration reduction performance of the tire, but also cause excessive deformation of the tire, reduce the contact area with the ground, and normal wear can only be borne by the central part of the tread, resulting in early wear.
2. Excessive wear on both sides of the tire (shoulder): The main reason is insufficient inflation or long-term overload driving. When the inflation volume is small or the load is heavy, the contact area between the tire and the ground is large, so that both sides of the tire contact the ground and participate in work, resulting in early wear. When the tire pressure is 20% higher or lower than the rated value, the mileage loss is 20% to 25%.
3. Excessive wear on one side of the tire: The main reason is misalignment of the front wheel. When the camber angle of the front wheel is too large, the outer side of the tire forms early wear, and when the camber angle is too small or there is no camber angle, the inner side of the tire forms early wear.
4. The shoulders of the left and right front tires are worn in a wavy manner, and the inner side of the left rear wheel and the outer side of the right rear wheel are worn abnormally and seriously. The main reason is that the front and rear axles are not parallel, and the wheelbase on the right side is larger than the left side, which exceeds the standard. The maximum difference between the left and right wheelbase standards (measured at the front and rear axle leaf spring seats) is 4mm. The solution is: the leaf spring car can be solved by screening and adjusting the leaf spring length. The air suspension car adjusts the thrust rod length.
5. The shoulders of the left and right front tires are worn in a wavy manner, and the inner side of the right rear wheel and the outer side of the left rear wheel are worn abnormally and seriously. The reason is that the front and rear axles are not parallel, and the wheelbase on the left side is larger than the right side, which exceeds the standard.
6. The shoulders of the left and right front tires are worn in a wavy manner, and the rear wheels are normal (sometimes abnormal wear of the shoulders of individual rear tires can be seen, but they are replaced from the front wheels). The main reasons are incorrect toe-in value, serious wear and tear of the steering straight tie rod ball head, looseness, slight wheelbase error exceeding the standard, and the front wheel has a tendency to shimmy. The radial tire is 0-2mm, and a 1mm toe-in value error can lead to a 7% mileage loss. Vehicles with a tendency to shimmy on the front wheels are caused by poor front wheel caster angle, offset value, etc. The front axle kingpin thrust bearing can be replaced with a damping bearing or the kingpin caster angle can be increased by 1 degree.
7. The right front wheel shoulder is severely worn in a wavy manner, the left front wheel is often slightly worn, and the other wheels are normal. The main reason is that the steering tie rod ball head is loose.
8. The outer shoulder of the right front wheel is severely worn in a wavy manner. The outer side of the left rear wheel is abnormally worn. Or the outer shoulder of the left front wheel is severely worn in a wavy manner. The outer side of the right rear wheel is abnormally worn. The front and rear axles are parallel, but the center lines are inconsistent. The wheelbase error is not large, but the diagonal error is large. Wheelbase diagonal standard (measured at the front and rear axle leaf spring seats): the maximum difference is 5mm.
9. The tires are evenly worn but the wear is large, and there is no eccentric wear or wave wear.

The general reason is that the road condition is poor, the mountain road is winding, and the tire pattern is not suitable for special roads. Concrete pavement and anti-skid asphalt pavement wear tires faster than ordinary asphalt pavement, so choose the right tire pattern.

Improper maintenance by users, mixed tires, and no timely tire replacement can increase mileage by 20%.

Severe overloading causes tire overload, and the tire load rate is reduced under harsh conditions.

The higher the ambient temperature, the lower the tire life. The tire tread life can be 4 times higher under 4-degree temperature conditions than under 32-degree temperature conditions.

10. Alopecia areata wear on tires: The reason for alopecia areata wear on individual parts of the tire is poor tire balance. When an unbalanced wheel rotates at high speed, individual parts are subjected to great force, wear is accelerated, and steering shakes, and handling performance deteriorates. If a slight shake is found in a certain speed direction during driving, the wheel should be balanced to prevent alopecia areata wear.

In order to avoid the above abnormal wear and tear, we should pay attention to the following matters:

1. Pay attention to tire pressure: Air pressure is the lifeline of tires. Too high or too low pressure will shorten its service life. If the air pressure is too low, the tire body will be deformed, cracks will easily appear on the sidewalls, and flexion will occur, resulting in excessive heat generation, rubber aging, tire layer fatigue, and cord breakage. If the air pressure is too low, the tire contact area will increase and accelerate the wear of the shoulder. If the air pressure is too high, the tire cord will be stretched and deformed excessively, the elasticity of the tire body will decrease, and the load on the car during driving will increase. If it encounters an impact, it will cause internal cracks and explosions. At the same time, too high air pressure will accelerate the wear of the crown and reduce the rolling resistance.
2. Check the front wheel alignment regularly: The front wheel alignment has a great impact on the service life of the tire, especially the front wheel toe and front wheel camber. The front wheel camber mainly accelerates the wear of the shoulder, that is, eccentric wear; too small or too large front wheel toe mainly accelerates the wear of the inside and outside of the tire.
3. Pay attention to your driving style: In addition to handling the situation, drivers should choose the road to drive on, avoid sharp stones, glass, metal and other objects that may puncture and scratch the tires, and avoid chemical spills that adhere to and corrode the tires. When driving on a road with a large camber, try to drive in the middle to reduce the increase in the load on one side of the tire and cause uneven tire wear.
4. Avoid overloading: Under normal circumstances, overloading by 20% will reduce the tire life by 30%, and overloading by 40% will reduce the tire life by 50%;
5. Rapid turns, emergency braking, high-speed starting and rapid acceleration will all affect the damage of the tires, which are what drivers should avoid while driving.

(I) Possible impacts and consequences of various angles

1. Toe angle. Too much positive toe will cause the tire to wear out quickly. The wear form is sawtooth shape. For radial tires, there will be a similar wear form caused by too much positive camber. When you touch the inner side of the tire from the inside to the outside, you will feel the sharp inner edge of the tread. The steering is unstable, the straightness is poor, and the wheel shakes. Too much negative toe will cause the inner side of the tire to wear out quickly. The wear form is sawtooth or block shape. For radial tires, there will be a similar wear form caused by too much negative camber. When you touch the outer camber of the tire and touch the inner edge of the tread from the inside to the inside, you will feel the sharp inner edge of the tread. The steering is unstable, the straightness is poor, and the wheel shakes.
2. Kingpin caster angle. Too small caster angle will cause instability, lack of steering wheel automatic return ability, and drifting when the speed is too high. Pay special attention on the highway. Asymmetric kingpin caster angle will cause deviation. The kingpin caster angle of the left and right wheels differs by 0.5 degrees, and the vehicle will deviate.
3. Wheel camber angle. Too much positive camber angle will cause unilateral wear on the outer side of the tire, accelerate the wear of the suspension system, and the vehicle will deviate to the side with a larger positive camber angle. Too much negative camber angle will cause unilateral wear on the inner side of the tire, accelerate the wear of the suspension system, and the vehicle will deviate to the side with a larger positive camber angle.
4. Steering angle. If the steering front angle exceeds 1.5 degrees, the vehicle will deviate, and the deviation direction will be toward the side with a smaller wheelbase.
5. Setback angle. When the setback angle reaches a certain level, the vehicle will deviate, and the deviation direction will exceed the side with a smaller wheelbase.
6. Thrust angle. The thrust angle will cause tire wear, steering misalignment, steering wheel deflection, deviation, and the body of the vehicle will go straight at a crooked angle.

(II) Summary and analysis of various symptoms

1. The front wheel caster angle is asymmetrical, the deviation exceeds 0.5 degrees, and the vehicle deviates to the side with smaller caster angle.
2. The front wheel camber angle is asymmetrical, the deviation exceeds 0.5 degrees, and the vehicle deviates to the side with the largest front wheel camber angle.
3. The rear wheel camber angle is asymmetrical, the deviation exceeds 0.5 degrees, and the vehicle deviates to the side with the smallest rear wheel camber angle.
4. The change of vehicle wheelbase can be observed according to the front and rear axle setback angles. When the sum of the front and rear setback angles exceeds 0.2 degrees, there will be a perceptible deviation, and the deviation will be towards the side with smaller wheelbase. In addition, there are other factors that the four-wheel alignment instrument cannot detect.
5. Side slip, mostly caused by tires.
6. Uneven tire pressure.
7. Asymmetrical brakes, slipping.
8. Unbalanced steering assistance.
9. Wear and misalignment of suspension system parts.

Note

Since the four-wheel alignment instrument cannot detect all the deviation factors, sometimes it is possible that everything seems normal from the alignment instrument, but the vehicle still deviates. This requires item-by-item inspection. In the actual four-wheel alignment service practice, it is often encountered that the vehicle originally did not deviate or deviated slightly, but after adjusting the front wheel toe, it deviates or deviates more. People easily attribute this phenomenon to the adjustment of the toe. In fact, because the vehicle is always in a position where the toe of the left and right wheels is equal when driving straight, the front wheel toe itself will not cause deviation. However, if the front wheel toe is not correct, the friction between the tire and the ground will increase, which can cover up the deviation. In fact, the vehicle has already had a tendency to deviate due to other reasons, but it is just covered up. When the deviation plaque is covered up, it often shows that the tire is more seriously eaten. At this time, if the deviation factors are not comprehensively analyzed and the toe adjustment is blindly performed, the deviation fault that was not serious originally will be highlighted, so it must be comprehensively analyzed and rectified.

(III) Summary of the causes of fetal eating

1. The front wheels eat the inner or outer sides at the same time, and the front wheel toe is incorrect.
2. The front wheel eats the tire alone, and the front wheel camber angle and toe angle are incorrect.
3. The rear wheel eats the tire, and the wheelbase toe angle is incorrect. In addition, there are other factors that the positioning instrument cannot measure.
4. The driver has bad driving habits.
5. The tire pressure is too high, which will eat near the center line of the tire tread.
6. The tire pressure is too low, which will eat both sides of the tire at the same time.
7. It may cause problems with the chassis parts.

(IV) Causes of vehicle drifting:

The castor angle is close to zero or negative.

(V) Causes of the steering wheel becoming heavy:

The castor angle is too large, the camber angle is incorrect, and the suspension parts are deformed after being overloaded.

(VI) The vehicle falls when encountering slight bumps or accelerating,
mainly due to incorrect rear wheel toe angle and wheelbase.