Light steering shimmy

broken scope

broken scope

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Dec 28, 2018
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Tennessee
I have a 06 Jeep rubicon that has a 4in rc lift with rc fixed control arms that has a steering shimmy at 50 to 60 mph. I had two sets of new at tires put on and balanced and road force balanced. Put all new parts and Zj upgrade. Only thing I know left to do is change out the control arms and get adjustable to change the caster. The alignment shop showed I have a 6.3 caster. Do you think this could be my problem? Thanks by the way it has never been off road.
 
Pinion angle is more important then Castor!!!!!!
Rough Country a lot of times will include a drop pitman arm. Do you have that installed?
Also I would try swapping the fronts to the Rears because shimmies are almost always caused buy out of balance tires. And tire shops never take the time to balance tires perfectly and jeeps require perfectly balanced tires.
 
Have you check tie rod ends and drag link ends? Loose control arm bolts? Those can also lead to a shimmy.

More often than not though its a balance issue.

alignment01.jpg
 
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No dropped pitman arm. Rotated and all that. Two new sets of tires also. First set got replaced because dealer thought tires were bad because shimmy wouldn’t go away. Also tried road force balance at discount tire. So balanced a total of four times all together. Tires are 33in toyos.
 
Yes Tworley I checked and replaced all that. I replaced hub bearings all tie rod ends upper control arm bushings,track bar bushing and ball stud on adjustable track bar,tie rod zj upgrade and new drag link. Fixed lower control arm bushings look goos as does ball joints.
 
broken scope said:
No dropped pitman arm. Rotated and all that. Two new sets of tires also. First set got replaced because dealer thought tires were bad because shimmy wouldn’t go away. Also tried road force balance at discount tire. So balanced a total of four times all together. Tires are 33in toyos.
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I'm in the same boat, Multiple balances and rotations. Another brand new set of tires (swapped Coopers for BFG's). ZJ steering upgrade. Ball joints and unit bearing seem fine. Still have a shimmy around 45mph.
I almost wonder if my lug bolt holes are wallowed out on the wheels. Don't they balance them with a tapered adapter thru the center hole? I do need to replace my control arms, as the bushings look pretty worn.
 
broken scope said:
Fixed lower control arm bushings look good as does ball joints.
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Look good or are good? Two different things...

A failing ujoint can also cause a slight shimmy/wobble but that would be more noticeable on long sweeping turns.
 
Can you describe your shimmy more? Is it like a vibration, or...

How new is the lift? Did this start happening soon as you lifted or did it start later?

6.3 seems really specific, but that is close to what it is stock I believe, so I am not sure caster is your issue. Although as you said, it isn't adjustable, but I am not sure that even if you had adjustables it would make that much of a difference.

Try measuring the squareness of your front axle. You want to make sure it is centered, and the same with the rear. If your rear is not centered it can cause a walking situation. Although not really a shimmy, so we need more clarification on what you are actually feeling.

Measure from the front of your axle tube to the center of your skid plate bolt. In the sameish spot on all 4 corners and make sure your axles are centered. Also make sure they are not too far left or right under the vehicle too. I am not sure if they check for that at the alignment shop.

What shocks are you running on it?

If you did just get the lift, and you ran to the alignment shop. Maybe give it a month for everything to settle in. Your springs will settle, and it may calm down on its own.
 
Ball joints and control arm bushings are good. I bought the Jeep already lifted about 3 Year’s ago. Lift has about 4000 miles on it is all. Had some mickey Baja tires on it when I got it and the cupped really bad but rode ok. So it didn’t start unti about 3000 miles after the lift. The shimmy I feel in the steering goes back and forth like a 1/4 inch and I can see the passenger seat moving or vibrating. The shocks are stiff rc shocks that were in kit.
 
I am not convinced of the tires yet. I have had all of that done too at Discount tires like 6 times then went to 4 wheel parts, and they fixed it first try. The road force balance is only as good as the tech doing it. And 4 wheel parts didn't have a road force balancer, and still did a better job than Discount tire which had.

A good test of the tires is rotate them front to back and see if the shimmy goes with it. Or changes.

Also a bad ujoint can cause what you are saying too. I would look at the front and rear drivelines and make sure they are timed correctly, and that the ujoints are free and not stiff. Maybe pull the front driveline completely out and driver it around.
 
I put new joints in the front axles but not the drive shafts. I looked for play and didn’t see any. Pulling the front out sounds like a good idea. I already rotated the tires around even throwing in the spare with no noticeable changes.
 
May not be your case, but I'll throw out some causes for my shimmy I was fighting years ago.
I had almost death wobble twice on two different occasions. I say almost because I did not let it get that far. I slowed way down till it stopped, then took the backroads home slowly. But, it would of happened. A dry steering test identified the problem. Both times it turned out to be the frame side track bar mount had loosened. Even with the cotter pin installed, things loosened up a bit. After the second tightening, it never did it again.
But, I always had the slightest shimmy at around 45mph that I hated. Tires were 33" Toyos on cheapo steel wheels. Re-balancing would make it better, but not go away completely. It got worse again after wheeling aired down until I went back for a re-balance. When I would swap on my old Rubicon alloy wheels for the winter, there was never any shimmy whatsoever. I blame it more on the steel wheels than the heavy a$$ Toyos. I run Toyo MTs on my pickup with alloy wheels and they run true.
When I went to 35's (Pro-Crap), at the same time I did the rear Dana 44 swap, I mounted them on a new set of alloy wheels. I have never had a shimmy since. After many many years of wheeling aired down, I never needed a balance until the ProComps wore out and I had my current MTRs installed. Still wobble free.
I am not sure what kind of wheels you are running, and that may not be your problem. Just throwing my experience out there because I know how frustrating it can be. I have had other TJ buddies go through the same thing.
 
broken scope said:
I have steel black rock rims that are lug centric. I may have to change them out if l can’t find the problem.
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Most aftermarket wheels, all of mine included, are lug-centric and that's not your problem. No need to go to hub-centric.

Steel wheels are easy to bend/dent while offroading, are yours either of those? I had nothing but dented/bent/out of balance conditions when I stupidly switched to steel wheels 15 or so years ago. It was maybe a year later I went back to aluminum wheels.

And don't believe for an instant that your speed-sensitive shimmy may not still be tire balance related. Not many tire shops are good at getting big Jeep-size tires balanced so there are no speed-sensitive shimmies. Even after two sets of tires being balanced multiple times.
 
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Ive brought my MTRs in six or 7 different times before I finally saw the machine 0 everything out. I told them "I am not in a hurry, take your time and make sure its correct, this is the upteenth time Ive been in here".
 
My shimmy/wobble was caused by the tire not being round. The machanic that diagnosed my problem told me that it is not an uncommen issue with bigger tires. He recommends have new tires checked for true after a 50 mile break in. Ive bought tires 3 times and had at least one out of round each time.
 
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