Shimmy when hitting bumps/dips

[NCLife]

NCLife What is your caster set at?

I’m at -1 at the hole on either side of the diff…..so my caster is 7.

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[RodRecket]

That seems WAY to much... I had a terrible DW issue with my daughter's JK. I installed the correction brackets and "turned it up to 11" (3rd hole in the UCA bracket). I measured her caster at 7.3 and her wobble was worse... turned it back to 6, which doesn't seem like much, but it made a world of difference.

That is too much caster. My point was to show how much geometry correction brackets with the mopar lift (longer) LCAs moves the axle. However, my JT did not demonstrate any signs of death wobble with this combination.

My final iteration combined AEV geometry correction brackets and stock LCAs which gave me 5.4 and 5.3. Driving wise I don't feel much of a difference. It drives well and I know I'm within spec for piece of mind.

I did eventually get a little shake over certain expansion joints which came down the stock tie rod getting loose. Decided to upgrade the tie rod and drag link and have not had any DW issues. Drives very well for a lifted solid axle vehicle.

Summary of suspension parts:
Mopar 2", TF 1" spacer, AEV geo correction brackets, stock LCAs (all CAs are stock), TF track bar, tie rod, ad drag link, Fox TS stabilizer flipped, EVO mfg rear track bar.

 

[OHJeeper]

That is too much caster. My point was to show how much geometry correction brackets with the mopar lift (longer) LCAs moves the axle. However, my JT did not demonstrate any signs of death wobble with this combination.

My final iteration combined AEV geometry correction brackets and stock LCAs which gave me 5.4 and 5.3. Driving wise I don't feel much of a difference. It drives well and I know I'm within spec for piece of mind.

I did eventually get a little shake over certain expansion joints which came down the stock tie rod getting loose. Decided to upgrade the tie rod and drag link and have not had any DW issues. Drives very well for a lifted solid axle vehicle.

Summary of suspension parts:
Mopar 2", TF 1" spacer, AEV geo correction brackets, stock LCAs (all CAs are stock), TF track bar, tie rod, ad drag link, Fox TS stabilizer flipped, EVO mfg rear track bar.

I like your final build... seems solid. When you say "stock LCAs" do you mean the ones that came with the MOPAR kit, or the original ones from the factory?

Is just the stabilizer flipped or the draglink?

 

[RodRecket]

I like your final build... seems solid. When you say "stock LCAs" do you mean the ones that came with the MOPAR kit, or the original ones from the factory?

Is just the stabilizer flipped or the draglink?

Stock LCAs like what came on my Sport S from the factory. The Mopar kit has extended arms which, in combination with the geo correction brackets, caused the high caster numbers.

The stabilizer is relocated above the drag link.

 

[NCLife]

That is too much caster. My point was to show how much geometry correction brackets with the mopar lift (longer) LCAs moves the axle. However, my JT did not demonstrate any signs of death wobble with this combination.

My final iteration combined AEV geometry correction brackets and stock LCAs which gave me 5.4 and 5.3. Driving wise I don't feel much of a difference. It drives well and I know I'm within spec for piece of mind.

I did eventually get a little shake over certain expansion joints which came down the stock tie rod getting loose. Decided to upgrade the tie rod and drag link and have not had any DW issues. Drives very well for a lifted solid axle vehicle.

Summary of suspension parts:
Mopar 2", TF 1" spacer, AEV geo correction brackets, stock LCAs (all CAs are stock), TF track bar, tie rod, ad drag link, Fox TS stabilizer flipped, EVO mfg rear track bar.

Is the general consensus that every setup on a Jeep is different and therefore the amount of caster that will feel right is different? I've seen the statement in here that 7 or higher is too much, but is that some proven data point, or what was right for one persons rig? Also, what we be the indication your caster is too high?

 

[ShadowsPapa]

Is the general consensus that every setup on a Jeep is different and therefore the amount of caster that will feel right is different? I've seen the statement in here that 7 or higher is too much, but is that some proven data point, or what was right for one persons rig? Also, what we be the indication your caster is too high?

Too much can actually cause wear when turning, and can CAUSE wobble.
It's called, literally, caster shimmy or wobble.
A wheel is also less stable if out of balance AND too much caster. That's because now it's trailing and any lateral forces can move it back and forth - there's nothing but road force to keep it in line.
What may be a sign it's too high? Shimmy, wobble, tire wear. I've got the tire wear bit saved in the house and will try to remember to grab it later.

It's going to vary - geometry matters, it rules.
I was taught that in college auto suspension/steering classes and it's "out there" on pro sites as well these days.
Bigger tires with too much caster and/or too much toe is going to cause, not resolve, DW or shimmy in general.
This bunk of "more is better" is what may be causing some of the DW out there.
Iv'e got a great explanation I need to post - from a steering expert, how it works with toe, caster and SCRUB RADIUS - any being off, or being off in combination where each alone might be "ok" can cause DW or shimmies.
The IH truck people say it, auto/truck sites say it, and yet in forums, it's naw, more is better!

Get beyond the point where it steers decent - taking it beyond that is sort of silly - why? Especially when you don't "need it". If it works with 5.5 degrees I've never understood the desire to take it to 6 because that's better. No......... not necessarily.

I think this is another one of those areas where what the YT certified master techs say ends up being fact because it's said in 100 places and they make fancy YT videos that are attention grabbers as proof. You need MORE caster!
No, you don't. If it's got a problem, there are several other things that can cause that problem that too little caster can cause. But the answer, the rallying cry is always MORE CASTER.

If the truck goes straight - why try for more? If it doesn't - why not look for all of the other likely causes?

 

[Darkspeed]

Mine caster is 7.3 using the factory arms and the middle hole on the rancho geo brackets on a 3” lift. Drives /steers great now. I wonder if I should move up a hole in the Rancho to reduce the caster.

 

[mdyucca]

With front end drivability concerns and you can’t Identify any specific worn or loose component this has helped me. Install EVO Geometry correction brackets, MetalCloak Duroflex lower control arms and set caster to 6.5.

 

[notoriousms33]

Updating my last post after installing the terafelx drag link and tie rod. The steering has definitely improved and the shimmy is gone. I had a specific spot that I would would get a little wobble and it's gone now after the upgrades.

FYI Teraflex track bar, drag link, tie rod, MOPAR 2", AEV geo brackets, EVO rear track bar

My 21 Mojave stock height on 35s I have noticed has started with a slight wobble. Although Mojave comes slightly lifted, with it being stock- do you think this aev geo brackets will help support lateral moving pieces and improve the trucks driving?

 

[notoriousms33]

My 21 Mojave stock height on 35s I have noticed has started with a slight wobble. Although Mojave comes slightly lifted, with it being stock- do you think this aev geo brackets will help support lateral moving pieces and improve the trucks driving?

Took my gladiator to an off road shop, apparently when they did an alignment, the tow was off, causing the front track bar bushings to wear.

 

[RodRecket]

My 21 Mojave stock height on 35s I have noticed has started with a slight wobble. Although Mojave comes slightly lifted, with it being stock- do you think this aev geo brackets will help support lateral moving pieces and improve the trucks driving?

They are meant to realign the CA geometry after lifting so I don't think they'll do much for you on a stock suspension. I'd be more concerned with looking for worn stock steering components. My drag link and tie rod had some play in them within 30k miles (had some tough trail miles on them too)

 

[notoriousms33]

They are meant to realign the CA geometry after lifting so I don't think they'll do much for you on a stock suspension. I'd be more concerned with looking for worn stock steering components. My drag link and tie rod had some play in them within 30k miles (had some tough trail miles on them too)

I have about 34k on mine so that makes sense.

I took it in to an off road shop, and they said my track bar bushings are worn. Whats your recommendation on brands for new track bar?

 

[notoriousms33]

I have about 34k on mine so that makes sense.

I took it in to an off road shop, and they said my track bar bushings are worn. Whats your recommendation on brands for new track bar?

Also after getting a report from an alignment they noted my casters were off by -3.9 on each side. But they said that wouldn’t disturb the ride. Would aligning a track bar help get that straightened out?

 

[RodRecket]

I have about 34k on mine so that makes sense.

I took it in to an off road shop, and they said my track bar bushings are worn. Whats your recommendation on brands for new track bar?

So I'm on my second JT now, and though I liked my teraflex bars this time around I'm going with synergy. My rational is simply the design of their adjustment sleeve. I didn't care for the jam nut style tie rod of the TF bar and had them loosen up on me twice.

Though I'm not a huge brand loyalist the big advantage to staying with one manufacturer having parts work with each other. I frankenlifted my last JT and it rode nice but I had some headaches in between figuring out which brands worked together and which didn't.

That being said I have an AEV lift and they don't make steering components for the JT. For the additional components I plan on adding I'll stay with synergy.

 

[IzzyO]

So I'm on my second JT now, and though I liked my teraflex bars this time around I'm going with synergy. My rational is simply the design of their adjustment sleeve. I didn't care for the jam nut style tie rod of the TF bar and had them loosen up on me twice.

Though I'm not a huge brand loyalist the big advantage to staying with one manufacturer having parts work with each other. I frankenlifted my last JT and it rode nice but I had some headaches in between figuring out which brands worked together and which didn't.

That being said I have an AEV lift and they don't make steering components for the JT. For the additional components I plan on adding I'll stay with synergy.

Just wondering if you're using the full AEV dualsport lift kit (2.5/3 ~ High capacity?) and how you like it?

I've got a constant load from tent/rack & gear that I need to do something different asap because stock springs/lift just isn't cutting it weight wise anymore. I still do enough off road that I'm also wondering how the lift will perform over rocks etc.

I have been seriously considering doing a teraflex lift with AEV High Capacity springs or going with clayton 2.5 overland plus. But still open to going AEV dualsport and just saw your comment/hoping for some input.

Which steering components are you going to put on from synergy?


Thank you,

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