How to Solve Uneven Tire Wear of Semi-trailer?
The uneven wear of tires of heavy vehicles such as semi-trailers is relatively common. Most of the tires are severely worn on the inner and outer sides, that is, the tire edges are easily worn. The wear of the middle of the tire is relatively rare. The main reasons for the wear of the semi-trailer tire are as follows:
1. The front wheel (steering wheel) of the semi-trailer is worn
The straight travel positioning adjustment is not in place, and the tires are not in the straight travel position when the steering wheel is returned to the position and the steering gear is returned to the zero position.
2. Inspection and adjustment of straight positioning of semi-trailer
Return the steering wheel to return the steering gear to the zero position, and keep the steering gear in the zero position until the entire adjustment is completed.
Note: If the steering wheel is in the zero position and the steering wheel is not fully returned, it indicates that the steering wheel is not straight, and the steering wheel should be adjusted after the entire adjustment is completed. The logos are aligned, and the logo on the case is the middle one of the three bumps.
Use a jack to jack up the front axle so that the front tire can turn freely off the ground. Select a point on the front of the semi-trailer tire, in order to accurately mark the point, mark a "X", and the intersection of the "X" is used as the measurement point.
Measure the distance from the point to the semi leaf springs, and record the value A; turn the tire 180° to make the measurement point turn to the front, and 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 connection between the steering tie rod and the spline nut of 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, turn the ball head, and 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 does not cause the tire to swing again, drop the jack to make the tire touch the ground, then tighten the connection between the tie rod and the rocker arm, and tighten the clamp. At this point, the tires had been adjusted to the straight position.
3. Inspection and adjustment of semi-trailer toe-in
Note: Before toe-in inspection and adjustment, make sure that the front wheel has been adjusted.
With the front wheel in the straight position, use a jack to lift the front axle so that the front tire can rotate freely when off the ground. Choose a point at the front of the tire, in order to accurately mark the point, mark a "X", and the intersection of the "X" is used as the measurement point.
Measure the distance between the points on the two front wheels and record the value A; turn the tires 180° to turn the measurement point to the front, and then measure the distance between the measurement points 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 one end of the ball head on the steering tie rod of the front axle to connect with the spline nut of the front axle, so that the right front tire of the semi-trailer can swing freely. Adjust the right front wheel, and measure A and B again until B-A meets the specification requirements. After the adjustment, loosen the clamp of the steering tie rod, turn the ball head, adjust the length of the tie rod, and loosely install it on the front axle. If the tightening operation does not affect the position of the front wheel again, drop the jack to make the front wheel touch the ground, then tighten the connection between the ball head of the tie rod and the spline nut of the front axle, and tighten the clamp bolt.
4. Inspection and adjustment of the wheelbase of the semi-trailer
Take the 6X4 model as an example. Select 1 measurement point on the left and right symmetrical positions on the front wheel, middle wheel and rear wheel, and then measure the data A, B, C, and D as shown in the figure below.
Analyze the measurement results as follows:
If A≠B, indicate that the distance between the two middle wheels on the left and right sides to the center of the rear leaf spring is unequal and needs to be adjusted.
If C≠D, indicate that the two rear wheels on the left and right sides are not spaced from the center to the rear half of the yellow center, which needs to be adjusted.
Take C>D as an example to illustrate the adjustment method: select the side with the short center interval 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, according to the actual situation, Install 1-2 washers with a thickness of 2mm to make the right tire move backwards, increase D to make C≈D, and finally tighten the connecting bolts of the lower thrust rod and the thrust rod support.
5. Inspection and adjustment of semi-trailer tire runout and swing
Use the measuring tool to add a benchmark to the base, as shown in the figure below. Since the tool is relatively simple, it can be self-made.
The method of jump check is as follows: use a jack to jack up a bridge so that the tire can rotate freely. Put the tool on the side of the tire tread, turn the tire, find the point on the tire that is closest to the ejector bar, make the ejector bar push against this point, and fix the tool; turn the tire to find the point on the tire that is farthest from the ejector bar , measure the distance from the ejector rod to this point, which is the runout of the semi-trailer tire.
If the amount of runout or swing is greater than 2mm, on the premise that the joint nuts, leaf spring riding bolts and other components are not loosely connected and tightened, there is a quality problem in the tire or steel ring, and it can be changed and adjusted.
A quick way to check whether the tire is unevenly worn: The method after the adjustment is as follows:
Spray the surface of the tire with self-spraying paint or brush the car topcoat. After the paint is dry, choose a flat and dry road to stop the road test. The driving interval is more than 2 kilometers. Stop and check the spray paint. If the paint wear is even, especially the outer edge of the tire under no load No paint peeling at all, indicating that the tires are no longer worn.
Note: The air pressure of semi-trailer tires is 8.6bar, but most vehicles actually inflate the air pressure above 13bar due to overloading requirements, causing the crown to bulge. When the vehicle is empty, the two outer sides of the tires do not touch the ground. Under heavy load, the tire crown is pressed down, and the outer side of the tire is in contact with the ground sometimes but not, which cannot form rolling friction, resulting in the phenomenon of "rubbing". This also creates rapid wear on the outside of the tire to a certain level, causing wear on both the inside and outside of the tire.