Truck shake may be related to tire radial runout

Of all the shapes, round is the easiest to roll, so round wheels are chosen.

Theoretically the wheel should be perfectly round, but due to manufacturing level, wear and tear, assembly errors and other factors, tires are out of round to varying degrees.

When the out-of-roundness exceeds a certain limit, it will significantly affects the comfort of the vehicle while driving.

A lot of truck shake problems are related to out-of-round tires (also known as: radial runout). So it is necessary to master a correct radial runout measurement method. Radial runout is equal to the difference between the maximum radius and the minimum radius of the tire, and is required to be no more than 3mm, or else it will produce significant shaking problems. Both laser displacement sensor and percentage meter can measure the radial runout, but the former is more accurate.

Measurement methods and precautions are as follows:

▎Use of laser displacement sensors 

Measurement steps:

1. The vehicle to be tested shall be warmed up and driven for a period of not less than 2 km prior to the test in order to eliminate the deformation of the tires at rest. In the case of newly fitted tires, no warm-up driving is required.

2. Park the vehicle on a level surface and release the handbrake, use blocks of wood or other objects to prevent skidding at the front and rear of the wheels.

3. Support the axle corresponding to the wheel to be tested with a jack so that the wheel can rotate freely. It is recommended to use two jacks to support the left and right sides of the axle. A single jack should not be used to support the axle in the center of the vehicle, as this will cause the vehicle to sway from side to side when the wheel is turned, introducing errors into the data.

4. Support the displacement sensor with a tripod or other suitable support. The laser displacement sensor should not be shaken during the measurement process.

5. Move the sensor bracket so that the laser dot falls in the right position. Positioning requirements: the laser beam is parallel to the side of the tire; the beam passes through the center of the tire's circle; the point of light falls on the middle tread of the tire; if the number of treads is even, the middle two treads are measured separately.

6. Turn the tires as evenly as possible without using explosive force or using the engine to drive the wheels, as these practices will cause the vehicle to shake and affect the measurement results. For each measurement, rotate the tires no less than 5 revolutions.

7. Record the maximum value and minimum value during the test, and subtract the two to get the radial runout data.

▎ Use of percentage gauges 

Measurements with laser displacement sensors are fast and accurate, but the cost of the equipment is too high. From the economic and feasibility considerations, the selection of the percentage table can also achieve the measurement of tire radial runout. If the measurement method is correctly mastered, a high measurement accuracy can also be achieved.

Measurement steps:

1. The vehicle shall be preheated and driven for not less than 2km before the test to eliminate deformation of the tires at rest.

2. Release the handbrake after parking the car on a level surface and use blocks of wood or other objects to pad the wheels in front of and behind them to prevent skidding.

3. Support the axle corresponding to the tire to be tested with a jack so that the tire can be freely rotated. It is recommended that two jacks be used to support the left and right sides of the axle. Do not use a single jack to support the center of the front axle and support both wheels at the same time, as this will cause the whole vehicle to sway from side to side when turning the wheels, introducing errors into the data.

4. Place a square iron block with a mass of not less than 5 kg in front of and behind the test tire, requiring good contact with the ground without shaking. Then fix the dial gauge on this iron block through a magnetic base. The dial gauge must not shake during the measurement process.

5. Move the meter so that its measuring rod meets the following position requirements:

The percentage gauge should be parallel to the side of the tire; the extension of the measuring rod should pass through the center of the tire's circle; the front end of the measuring rod of the percentage gauge should be pressed against the middle of the tire's tread, and if the number of treads is even, the two middle treads should be measured separately.

6. Turn the tires at an even speed, do not use explosive force or use the engine to drive the wheels. These will cause the vehicle to wobble and affect the results.

7. Read the radial runout value:

The first one, for new tires that do not have a through-transverse pattern and are not used 

As the tire rotates, the data on the percentage gauge changes. The maximum and minimum values are read during one rotation cycle, and the difference between the two is the radial runout value. The measurement is repeated 3 times and the final result is averaged.

The second, for tires with through-transverse breaks 

When rotating the tire, you only need to record the reading at the middle of each tread. Find the maximum and minimum values among all numbers, and the difference between them is the radial runout value. The runout value measured by this method is slightly less than the actual value.

Precautions for measuring with a percentage meter: When taking continuous readings, if the maximum or minimum value occurs in a position where the value changes drastically, it is necessary to double-check whether such changes are caused by local defects If so, then this section of the data should be discarded directly.

If there is a radial runout of more than 3mm in the whole tire, it is recommended to replace that tire.