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Discussion Starter · #1 · (Edited)
Hi,

Two years ago I added to my JK;
- Dynatrac axles (front with extra caster angle)
- Teraflex 4" lift (shortarm) with elka shocks
- 37" BFgoodrich Tires on 17" Mickey thompson wheels

I experienced bumpsteer and death wobble since then, so I;
- Had everything aligned (twice)
- searched the internet for the cause (planman's youtube movies etc.)
- added a high steer kit
- raised my trackbar
- played with different air settings in the tires
- changed the steering stabilizer
- Gave the wheels more toe out


My conclusion;
- Lowering the air in my tires helps, but with the 3.8 it makes the Jeep to slow.
- I think the angle (see pic) of my trackbar and draglink is correct
- As far as I know there is no play at the bushings or anything else
- the steering stabilizers makes sure death wobble doesn't occur, but it's still there. It only works as a bandage.
- The toe out on the wheels made the tires wear out excessivly

I know bumpsteer and death wobble are two seperate things, but I experience both in my JK.

Who can help me out fixing this, because there is no decent shop over here which can cure my problem.

I'm actually debating on putting a full hydro kit on my JK if I can't solve my problem.


Please help.
 

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I never saw you mention weight distribution. I fought it as well. Getting your track bar and drag link parallel is a big deal. When I did that (Teraflex frame side drop for the track bar) it helped a lot. The other piece of the puzzle for me was changing the weight distribution. I added some spacers in the front to level the ride and it made a world of difference. Keep in mind that your axles have to shift as your springs compress. If you have a heavy rig and are front heavy (weight distribution too much toward the front) then it will play havoc with steering. It amazed me how much 1 inch on the driver and 1.5 inches on the passenger did for my ride (leveled gas tank at 1/2 full).
 

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I even have slight bump-steer with a hyrdro assisted ram setup, and I agree that it is due to my heavy front/light rear setup. I run no bumper,tire, or backseat so my ass end is a good .33" higher than my 10.5 recon/xrc bumper front.
 

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Does your steering wheel actually move ?My light weight 2 door fights the road/ruts but steering wheel is still.

Do you or a friend have a Gopro ?
Mount to the front cross member and see what's going on. http://youtu.be/DGVbULgCP14



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With your added caster with the Dynatrac you should not be feeling bumpsteer. Your angles dont look correct on your track bar but the picture cuts off the bump part up to the frame. Put a strait edge across it then take an angle reading. Eyeballing it can be missleading and burned me. Take a look at attached picture this will give you an idea. After the front is done the rear needs to match or you will get a loose feeling from the rear. Kind of feels like it is crab walking. I am taking for granted here that everything is tight in the front since you have a new front end also. I would still check your ball joints by jacking each wheel up a hair off ground then try rocking the wheels. Helps to have a second set of eyes here! Then have a buddy shake the front end from side to side while you crawl around under the front end and check all the other connections for movement. Just a tiny bit will get modified as it travels out especially with big tires and lifts!

Vehicle Car Automotive tire Wheel Auto part
 

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Hi,

Two years ago I added to my JK;

I experienced bumpsteer and death wobble since then, so I;
- Had everything aligned (twice)
- searched the internet for the cause (planman's youtube movies etc.)
- added a high steer kit
- raised my trackbar
- played with different air settings in the tires
- changed the steering stabilizer
- Gave the wheels more toe out
Why did you toe it out? How much?


With your added caster with the Dynatrac you should not be feeling bumpsteer.

What does caster and bump steer have to do with each other on a solid axle? Usually it's as simple as drag link and track bar arc lengths.

--


OP, are we talking a mechanical bump steer or someones interpretation of "i hit a bump and it sometimes wanders"? Bump steer is mechanical, unintentional turning of the wheels. As in the drag link and track bar aren't swinging in the same arc, therefore causing unintended steering as the suspension cycles. A test for this could be as simple as supporting the frame by jackstands, pulling the springs and cycling the suspension up/down while someone watches the steering wheel. As mentioned, it's easy enough to check that the drag link and track bar are in fact at the same angle, "eyeballing" it is not recommended.

This is the first time I've seen weight distribution and "bump steer" related, perhaps I've just been missing out on this. Perhaps we're talking about two different things as well.

Is your front axle centered?
 

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In my case aftermarket drive shafts and vib's forced me to take my caster back to about 0 degrees! Now when I hit a bump it does feed back to the wheel. Bump steer is always there to some degree and caster helps to negate it. Lifts and bigger tires amplify all of it. The sweet spot with caster is around 4 degees stock and around 6 degrees with a lift and or bigger tires. All of our modifications are a give and take world and sometime more take then give! You just need to find the Happy Happy Happy spot you can live with!
 

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In my case aftermarket drive shafts and vib's forced me to take my caster back to about 0 degrees! Now when I hit a bump it does feed back to the wheel. Bump steer is always there to some degree and caster helps to negate it. Lifts and bigger tires amplify all of it. The sweet spot with caster is around 4 degees stock and around 6 degrees with a lift and or bigger tires. All of our modifications are a give and take world and sometime more take then give! You just need to find the Happy Happy Happy spot you can live with!
How the hell does one deal with 0 caster? :eek:


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In my case aftermarket drive shafts and vib's forced me to take my caster back to about 0 degrees! Now when I hit a bump it does feed back to the wheel. Bump steer is always there to some degree and caster helps to negate it. Lifts and bigger tires amplify all of it. The sweet spot with caster is around 4 degees stock and around 6 degrees with a lift and or bigger tires. All of our modifications are a give and take world and sometime more take then give! You just need to find the Happy Happy Happy spot you can live with!
Hitting a bump and the wheel just "fluttering" or shaking is not bump steer.

Bump steer is when you hit a bump and the Jeep changes lanes.

Increasing caster can mitigate the fluttering affect when hitting bumps, slightly, but is not quite relevant in a discussion about bump steer.
 

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You try and tell my wife it is not bump steer! She will have some kind words for you! I don't think it is bad but when my geometry was off because of the previous owner it was BAD! Life changing bad on top of bad ball joints and I had just stuck the LS in it with never driving it! That was an interesting first run to say the least. The front axle wasn't even centered! Was pushed over to passenger side over and inch! You could see the springs leaning to that side! First jeep Wrangler I have ever owned along with it is modified and I am modifying it also! Was a very steep learning curve but love the JEEP!
 

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You actually did it .... Wow. Did you post a follow up ?


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Just that I had done it and that the uppers are grease-able and seemed stout. The lowers are not grease-able and don't seem like anything special, but I will eventually drill them and add grease fittings. So far they are holding up fine and my shit goes where i point it. Now if I can just figure out where the fucking intermittent shimmy is coming from......
 

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I will add to the to the high jack. I had a 45 to 50 mph vibration that I thought was the drive shaft hence turning my yolk up and negating my caster as previously discussed. This weekend I changed out my complete exhaust that I hay bagged for the LS install. Today no more vibration at 45 to 50? Could it have been a harmonic or drone that felt like a vibration? Maybe a multiple of drive train and exhaust? I have come to learn how intertwined and complex some of these systems have become! Was getting terrible gas mileage and black exhaust that is why I decided to change it out along with I could not find any other problems. Never had problems like this with my old trucks but they were pretty crude compared to all the new stuff!
 

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Bump steer is caused by ONE thing.

Messing with all of that other crap won't help you one little bit in regards to bump steer.

Define the problem. Determine why that problem is occurring. Address the root cause. It's that simple.

If bump steer is truly your problem, it's being caused by the drag link and track bars traveling differing arcs.
 

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Discussion Starter · #17 · (Edited)
Try to get a picture that shows both ends of each the track bar and the drag link. Its hard to tell angles for sure without being able to see the drivers side end of either of them.

RK
Thanks guys for all the replies. A lot to read, hopefully some answers to solving my problem.

Here's a pic to shows the angles. They look pretty parallel to me.
 

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Bump steer is caused by ONE thing.

Messing with all of that other crap won't help you one little bit in regards to bump steer.

Define the problem. Determine why that problem is occurring. Address the root cause. It's that simple.

If bump steer is truly your problem, it's being caused by the drag link and track bars traveling differing arcs.
So what you're saying is when my ball joints were worn out and I'd hit a bump causing my Jeep to steer into another lane without me asking it to or when all the grease blew out of my tie rod ends and I hit a bump and my Jeep steered my off the road and tried to kill me that wasn't bump steer either. It was just going over a bump and my Jeep steering itself, but not bump steer. OK, got it.
 

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So what you're saying is when my ball joints were worn out and I'd hit a bump causing my Jeep to steer into another lane without me asking it to or when all the grease blew out of my tie rod ends and I hit a bump and my Jeep steered my off the road and tried to kill me that wasn't bump steer either. It was just going over a bump and my Jeep steering itself, but not bump steer. OK, got it.
Bump steer has a very explicit definition in this application. You weren't experiencing bump steer, you were experiencing the results of crappy steering components.
 

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Discussion Starter · #20 ·
I never saw you mention weight distribution. I fought it as well. Getting your track bar and drag link parallel is a big deal. When I did that (Teraflex frame side drop for the track bar) it helped a lot. The other piece of the puzzle for me was changing the weight distribution. I added some spacers in the front to level the ride and it made a world of difference. Keep in mind that your axles have to shift as your springs compress. If you have a heavy rig and are front heavy (weight distribution too much toward the front) then it will play havoc with steering. It amazed me how much 1 inch on the driver and 1.5 inches on the passenger did for my ride (leveled gas tank at 1/2 full).
Teraflex bumper front with winch, LOD rear bumper with no rear tire. The Jeep is level. I don't really think this cause the problem, but I could be wrong
 
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