steering stabilizer
JK Junkie
Joined: Jul 2009
Posts: 2,343
Likes: 1
From: The San Andreas Fault
There also a few more things to consider.
As you raise the JK, the coupling of suspension and steering becomes larger because of the geometry of the links and rods. High steer kits and dropped Pitman help significantly, but they do not eliminate the coupling completely.
The suspension and steering have some built-in damping which is enough to dampen out most oscillations that occur with stock geometry and components (tires in particular). As the Jeep is lifted the suspension and steering coupling induces larger forces on the steering beyond its ability to dampen.Bump steer results as geometry of the suspension changes significantly more compared to the suspension. As you add more mass in the form of larger tires, it makes the situation even worse.
Every system has a resonant frequency, including the JK suspension/steering. Engineers design the system so that frequency either occurs outside common operating conditions (speed, lateral acceleration, etc) or at transitional conditions such as acceleration.
Adding mass to the system in the form of big wheels (rims + tires) changes the resonant frequency, typically into a common operating condition of the Jeep like 50-60 MPH cruising speed. Lifting the Jeep subjects the steering to larger forces via the suspension/steering coupling. A loose joint (faulty parts including the SS) reduces the effective damping of the system. That's why in some cases removing the SS eliminates the symptoms.
The principles are simple, but troubleshooting is complex because there are so many variables.
As you raise the JK, the coupling of suspension and steering becomes larger because of the geometry of the links and rods. High steer kits and dropped Pitman help significantly, but they do not eliminate the coupling completely.
The suspension and steering have some built-in damping which is enough to dampen out most oscillations that occur with stock geometry and components (tires in particular). As the Jeep is lifted the suspension and steering coupling induces larger forces on the steering beyond its ability to dampen.Bump steer results as geometry of the suspension changes significantly more compared to the suspension. As you add more mass in the form of larger tires, it makes the situation even worse.
Every system has a resonant frequency, including the JK suspension/steering. Engineers design the system so that frequency either occurs outside common operating conditions (speed, lateral acceleration, etc) or at transitional conditions such as acceleration.
Adding mass to the system in the form of big wheels (rims + tires) changes the resonant frequency, typically into a common operating condition of the Jeep like 50-60 MPH cruising speed. Lifting the Jeep subjects the steering to larger forces via the suspension/steering coupling. A loose joint (faulty parts including the SS) reduces the effective damping of the system. That's why in some cases removing the SS eliminates the symptoms.
The principles are simple, but troubleshooting is complex because there are so many variables.