Death jitter occurs in vehicles with integral bridge (hard bridge) suspension. Generally, when the vehicle speed reaches 40KM and above, the front wheel vibrates strongly (rolling pits) or brakes, the steering wheel starts to shake from side to side, and then high frequency Violent swings, the body also shakes left and right, and the chassis is also accompanied by rattling sounds. This state will become more intense as the speed increases, and will ease or disappear when the speed decreases.
An object will change its state when it is moving, and vibration will occur at this time, so various vibrations will appear when the car is running. When these vibrations are maintained at a certain frequency, there is no effect. When the vibration frequency changes and reaches a certain At the critical point, it will resonate, and when the vibration frequency is completely out of balance, violent vibration may occur, which is why the death vibration is formed. The Wrangler is a typical front and rear 5-link (4 control arms + 1 thrust rod) integral bridge + coil spring hardcore off-road vehicle. This structure is very suitable for modification and makes it have outstanding off-road performance. The movement of the tire will affect the other tire on the same axis, so its comfort and tracking are not as good as independent suspension, and the vibration will be greater.
Since it is a multi-link structure, it means that there are more fixed points for suspension connection. Each link is assembled between the girder and the bridge. The function of the control arm is to position the bridge forward and backward, and the thrust rod is to position the bridge left and right. , we can imagine what it would be like if the front and rear axles and springs carry the girder and the vehicle body while walking without parts to position the bridge. In theory, if they can achieve perfect balance, they can move forward by inertia. The extra wobbling will definitely start to vibrate abnormally immediately until it falls apart, because there is no fixed connection between the front and rear axles.
The relative position, angle and length of the connecting parts of the front and rear axles constitute the important parameters of the four-wheel alignment. Their status is extremely important and must be controlled within a reasonable range, otherwise there will be a series of control problems such as directional deviation. Most of the weight of the vehicle is supported by the coil springs of the front and rear axles. When the vehicle is driving normally on a flat road, the working state of all suspension components is relatively flat. When the vehicle is undulating, the springs and shock absorbers will be compressed more intensely. And stretching, in this state the angle and position of each control arm will change accordingly.
When the vehicle bumps, the tires first receive the impact, then transmit it to the bridge, and finally distribute it to the girder through each control arm. Cushioning, the control arm is cushioned by the rubber sleeve at the connection end, and the joint ball head can also perform force relief and cushioning by changing the angle. Of course, the cushioning effect of the spring and shock absorber cannot be ignored. Only when these components are combined together can they work efficiently Let the vehicle maintain good comfort and handling.
Through the above analysis, we believe that the cause of death vibration is vibration, so as long as the vibration of the chassis can be effectively suppressed, it can be solved. First check the dynamic balance of the tires. The deviation of the dynamic balance is caused by debris sticking to the wheel hub, falling off lead weights, aging tires and deformation of the wheel hub. Generally, the steering wheel vibrates slightly when driving. When the imbalance is serious, it will aggravate. The entire suspension forms a resonance, and once the resonance frequency is destroyed due to additional jitter, death jitter may occur.
We know that the vehicle will keep shaking up and down when the shock absorption fails. This is because the up and down buffering of the vehicle is all borne by the spring when the shock absorption fails, and the contact surface between the upper and lower ends of the spring and the beam is very small. Deformation in any direction, the damping limit spring without shock absorption can be compressed and stretched without restraint, the free shaking of the spring will aggravate the vibration of the vehicle, the failure of the shock absorption and the weakness of the spring are also one of the reasons for the death jitter. The steering rod and steering knuckle system are also the focus of inspection. The movement of the ball joint or the bearing will increase the steering gap, which is also a kind of abnormal vibration. During bumps, these vibrations will drive the front axle to swing. When it reaches a certain level, it may appear Death shakes. It is mentioned above that the function of the five-linkage is to position the bridge front, rear, left, and right. If the mounting end of the control arm moves, the bridge will move, which will cause instantaneous changes in the four-wheel alignment data and severe vibration. Each control arm The angle of the control arm will also change accordingly. The movement of the control arm is due to the aging and damage of the rubber sleeve or the wear of the joint ball head (fish eye), which can be solved by replacing the rubber sleeve or fish eye.
When the death shake occurs, the state of the front wheels is violently swinging left and right. Here we need to emphasize the thrust rod, which limits the left and right of the bridge. When the chassis is raised, the original vehicle thrust rod will make the front and rear axles shift to one side. In layman’s terms, the front and rear axles are not centered with the girder. At this time, the relationship between the front and rear axles and the girder is asymmetrical. Keeping this state for a long time will accelerate the loss of chassis components, such as rubber sleeves. The bridge will move left and right and cause death tremors. This probability is very high.
Many friends said that installing or replacing the modified version of the steering shock absorber can solve the death shake. This is a serious misunderstanding. This work is only to increase the steering damping to relieve the normal shaking of the steering wheel during bumps. It will have some effect, even if it is a palliative, not a permanent cure.
