Help with bump steer

[roaniecowpony]

Im fighting this battle now jeep was good then threw in the mopar lift then all hell broke loose so i did adjustable track bars front and rear tiny bit better my next though is lower control arms as ive been told the jl likes 6 degrees of caster my alignment sheet shows mine at 4.7. I have an fca case open they are on my third steering damper and have been told to be patient by 4 different jeep cares people i think they believe i am ghandi which i am not but if the new adjustable lca’s dont fix it im going to the steersmarts church and getting the drag link with the griffin attenuator and their tie rod. After that. If no luck. Trading it in

I don't think caster is the problem. 4.7 should be enough. The issue with putting more caster in is that it changes the pinion/driveshaft angle, probably in a direction that reduces U-joint life. The U-join angle increased with a lift. That angle could get bad enough to really cut the life of the U-joints if you increase the caster by rotating the pinion down. The only way to change one without affecting the other is by cutting the axle tubes and re-welding or buying a custom housing.

My opinion is that the tires have a natural frequency to oscillate, related to their size and weight, speed, and yes caster, etc., and if the steering system has enough flexibility, a bump can "excite" the system so it oscillates the tires (a.k.a. steering vibration, death wobble, etc.). If you change any of the components that contribute to the oscillation, you affect it. So, a change in weight and size of the tire/wheel increased the forces and your stock steering system flexibility was not up to the job of preventing oscillation.

Stiffening the steering system would be my approach. That includes a good aftermarket steering damper/stabilizer, stiffer track bar (including stiffer bushings) and possibly the drag link and tie rod, in that order.

http://www.fourwheeler.com/how-to/154-1307-do-the-harlem-shake-death-wobble/

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[Brooklynjlu2018]

I don't think caster is the problem. 4.7 should be enough. The issue with putting more caster in is that it changes the pinion/driveshaft angle, probably in a direction that reduces U-joint life. The U-join angle increased with a lift. That angle could get bad enough to really cut the life of the U-joints if you increase the caster by rotating the pinion down.

My opinion is that the tires have a natural frequency to oscillate, related to their size and weight, speed, etc., and if the steering system has enough flexibility, a bump can "excite" the system so it oscillates the tires (a.k.a. steering vibration, death wobble, etc.). If you change any of the components that contribute to the oscillation, you affect it. So, a change in weight and size of the tire/wheel increased the forces and your stock steering system flexibility was not up to the job of preventing oscillation.

Stiffening the steering system would be my approach. That includes a good aftermarket steering damper/stabilizer, stiffer track bar (including stiffer bushings) and possibly the drag link and tie rod, in that order.

I have this problem with the factory wheels as well but also it looks as if my drag link is making contact at some point dont know when with the splash shield seems if i added length to the control arms it would roll it back. No? Ill include a pic i was only thinking caster because i have the rancho hd track bars and the jeep drove fine last summer with the bigger wheels this problem has only appeared after the lift. The wandering problem was day one but the wheel shakes over every imperfection in the road

 

[roaniecowpony]

I have this problem with the factory wheels as well but also it looks as if my drag link is making contact at some point dont know when with the splash shield seems if i added length to the control arms it would roll it back. No? Ill include a pic i was only thinking caster because i have the rancho hd track bars and the jeep drove fine last summer with the bigger wheels this problem has only appeared after the lift. The wandering problem was day one but the wheel shakes over every imperfection in the road

If you add length to the upper, the draglink will roll forward & down, if you add length to the bottom, the draglink would roll forward and upward. If it were me, I'd just clearance the flange of the swaybar skidplate. I'd try to get at least 1/2" clearance. Then paint everything and check it from time to time to see if it is still making contact.

When you lift, it changes the track bar angle as well as the draglink angle. Did you do anything to correct these?

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