It is common for heavy truck tires to eat tires. Most of them eat tires on the inner and outer sides of tires, that is, eat tires on the edge of tires, and eat tires in the middle of tires is rare of tires wear.
The straight travel positioning adjustment is not in place, and the tire is not in the straight travel position when the steering wheel returns to the zero position and the steering gear returns to the zero position.
The toe in adjustment is not in place, the toe in value of radial tire is plus or minus 0mm, and that of bias tire is plus or minus 3mm.
Due to the accumulation of various tolerances, the wheelbase on both sides of the frame is unequal.
The quality problem of the tire or steel ring itself causes the tire to be seriously elliptical, and the contact force between the tire and the ground during rolling is uneven, accelerating wear.
Ideally, there is only rolling friction between the tire and the ground. However, due to the quality problems of the tire or steel ring itself, or the loosening of fastening nuts, leaf springs and riding bolts, the tire can not roll forward in a straight line, but swing left and right, resulting in sliding friction between the tire and the ground and accelerating wear.
Note: the inspection and adjustment methods listed below use simple tools. If there are professional tools, professional tools should be used to check and adjust more accurately.
Return the steering wheel, return the steering gear to the zero position, and keep the steering gear at the zero position until the whole adjustment is completed.
Note: if the steering machine is at zero position and the steering wheel does not return completely, it indicates that the steering wheel is not correct. After the whole adjustment, adjust the steering wheel again. The mark of correct zero return of the steering machine is that the output shaft of the steering machine is aligned with the scale mark on the housing of the steering machine. The mark on the housing is the middle of the three protrusions.
Jack up the front axle with a jack so that the front tire can rotate freely off the ground. Select any point on the front of the tire. In order to accurately mark the point, make a mark“ ×” Number“ ×” The intersection of No. is used as the measurement point.
Measure the distance from the point to the leaf spring and record the value a; Turn the tire 180 °, turn the measuring point to the rear, then measure the distance from the point to the leaf spring, and record the value B.
If | A-B | ≥ 2mm, the error is large, indicating that the front wheel is not straight and needs to be adjusted. The adjustment method is as follows:
Remove the spline nut connection between the steering tie rod and the steering gear rocker arm, adjust the tire position, measure the values of a and B again until a = B, then loosen the clamps at both ends of the steering tie rod, rotate the ball joint, adjust the length of the tie rod, and then assemble the tie rod to the rocker arm. At this time, in order to ensure that the following tightening operation will not cause the tire to swing again, drop the jack to make the tire land, Then tighten the connection between the pull rod and the rocker arm and tighten the clamp. At this time, the tire has been adjusted to the straight ahead position.
Note: before toe in inspection and adjustment, ensure that the front wheels have been aligned.
Keep the front wheel in the straight ahead position, jack up the front axle with a jack, so that the front tire can rotate freely off the ground. Select any point on the front of the tire. In order to accurately mark the point, make a mark“ ×” Number“ ×” The intersection of No. is used as the measurement point.
Measure the distance between the two front wheels and record the value a; Turn the tire 180 °, turn the measuring point to the rear, measure the distance of the measuring point, and record the value B.
The value of B-A is the toe in value. If it does not meet the standard requirements, it needs to be adjusted. The adjustment method is as follows:
Remove the connection between one end of the ball joint on the steering tie rod of the front axle and the spline nut of the front axle, so that the right front tire can swing freely. Adjust the right front wheel, measure a and B again until B-A meets the standard requirements. After adjustment, loosen the clamp of the tie rod, rotate the ball joint, adjust the length of the tie rod and loosely install it on the front axle. In order to ensure that the subsequent tightening operation will not affect the position of the front wheel again, drop the jack to ground the front wheel, and then tighten the spline nut connection between the tie rod ball joint and the front axle, Tighten the clamp bolts.
Take the 6×4 model as an example. Select one measuring point at the left and right symmetrical positions on the front wheel, middle wheel and rear wheel respectively, and then measure the data a, B, C and d according to the figure below.
The measurement results are analyzed as follows:
If a ≠ B, it indicates that the center distance of the two middle and rear leaf springs on the left and right sides is not equal and needs to be adjusted.
If C ≠ D, it indicates that the distance between the two rear wheels on the left and right sides and the center of the rear half yellow is different, which needs to be adjusted.
Take C > D as an example to illustrate the adjustment method: select the side with a short distance from the center of the rear leaf spring, that is, the right side of the vehicle (d), loosen the connection between the lower thrust rod and the thrust rod support on the rear axle, install 1-2 2mm thick washers according to the actual situation to make the tire on the right move backward, increase D, make C ≈ D, and finally tighten the connecting bolts between the lower thrust rod and the thrust rod support.
Use the measuring tool to add a benchmark to the base, as shown in the figure below. Because the tool is relatively simple, it can be made by yourself.
The runout inspection method is as follows: jack up a bridge with a jack so that the tire can rotate freely. Place the tool on one side of the tire tread, rotate the tire, find the point on the tire closest to the ejector rod, push the ejector rod to the point, and fix the tool; Turn the tire, find the farthest point on the tire from the ejector rod, and measure the distance from the ejector rod to this point, that is, the runout of the tire.
The measurement of shimmy is similar to the measurement of runout, except that the ejector rod shall be placed on the end face of one side of the tire for measurement, as shown in the following figure:
If the jump or swing is greater than 2mm, replace and adjust the tire or steel ring if there are quality problems on the premise that the connecting nuts, leaf springs, riding bolts and other parts are not loosened.
Method to quickly check whether the fetus is still eaten: after the adjustment, it is necessary to check whether the fetus is still eaten. The simple method is as follows:
The tire surface shall be evenly sprayed with self spraying paint or automobile finish paint. After the paint is dry, select a flat and dry road for road test. When the driving distance is more than 2km, stop and observe the painting. If the paint is worn evenly, especially the outer edge of the tire under no-load, it indicates that the tire is no longer eaten.
Note: the tire pressure is specified at 8.6bar. According to the actual use of Chinese users, it is generally about 11bar to meet the use requirements. However, most vehicles are in the need of overload. The actual inflation pressure reaches more than 13bar, resulting in the bulging of the tire crown. When the vehicle is unloaded, the two outer sides of the tire do not contact the ground. When it is overloaded, the tire crown is pressed down, The outer side of the tire is in contact with the ground from time to time, so it can not form rolling friction, resulting in the phenomenon of “edge rubbing”, which also causes rapid wear on the outer side of the tire to a certain extent, resulting in tire eating on both inner and outer sides of the tire. This problem should be explained clearly to the user.