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Old 03-25-2007, 04:09 AM   #1
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Question Track bar and DPA Geometry...

Gentlemen, I just installed a Fabtech 4" suspension lift and I have been learning a lot about the subject title. I read about TJ's not needing a DPA with up to 6" of lift. If this is the case, then why manufacturers such as Fabtech include one with their kits? My kit had me drill another hole 3/4 of an inch towards the driver's side and relocate the track bar. Ssome kits come with a relocation bracket...to me, drilling a hole and relocating it looks cheesy. I'm thinking about buying a heavy duty adjustable track bar and mounting it in the original location hole. I have not experinced the so called "bump steer", but I do experience severe steering wheel vibrations at speeds of over 40mph on uneven roads. My jeep is a 2006 SE with 33X12.5 on 15" rims. I'm stationed in Okinawa so I have "limited" off-road tech support. Your help is greatly appreciated.

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Old 03-25-2007, 09:32 AM   #2
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The general idea is to keep the track bar and drag link parallel. If you relocate or drop the track bar, you generally use a DPA in conjunction to keep the two parallel to minimize bump steer. However if you use an adjustable track bar, generally a DPA is not used. I've got 4" lift, no DPA and a JKS adjustable track bar and the bump steer is fine. Anything above 6" lift often uses a DPA because the angle of the TRE on the drag link becomes too geat.

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Old 03-25-2007, 08:04 PM   #3
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However at full articulation a lift of 4" will bind up at the stock pitman arm because it is outside of its range of movement. For 4" lifts I suggest a stock XJ pitman arm. It is right in between your stocker and the pitman arm they include.

You will read a lot on this board about this idea of not using a dpa with anything under 6". It's bad advice. Give Fabtech, or any other company that has engineered a suspension a call, and they will explain it.
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Old 03-26-2007, 12:39 PM   #4
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I'll side with those saying a DPA is not recommended for standard height lifts without a dropped upper trackbar mount also being installed. Fabtech would NOT be a company I'd call for advice on any Jeep lift, they're barely a second-tier player in the Jeep marketplace. And having worked for the parent company that owned ProComp, admittedly a crappy lift maker for Jeeps, I met a couple of their engineers at their Chula Vista that knew next to nothing about when TJs needed DPAs and when they did not. They just assumed it was similar to Ford, Chevy, Dodge, etc. since they had to be jack-of-all brands. Few really understand the changes made to Jeep steering with the TJ.
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Old 03-26-2007, 05:36 PM   #5
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My kit had me drill another hole 3/4 of an inch towards the driver's side and relocate the track bar. Ssome kits come with a relocation bracket...to me, drilling a hole and relocating it looks cheesy.
Just to echo Jerry's statement on this subject. I really wouldn't trust any lift manufacturer that would just tell you to drill a new hole in your trac-bar bracket and move it over to center the axle. I would bet that probably half of all lifted jeeps that develop death wobble have a stock trac bar that has been relocated and the hole that was drilled is wallowing out or cracking the bracket.
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Old 03-26-2007, 08:43 PM   #6
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Originally Posted by RedRubiTJ View Post
However if you use an adjustable track bar, generally a DPA is not used.

you were doing well in your advie unp to this point. no length of tracbar or adjustability in a tracbar will correct the steering geometry after a lift.

my advice, and the best advice, is to do both.
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Old 03-26-2007, 09:02 PM   #7
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you were doing well in your advie unp to this point. no length of tracbar or adjustability in a tracbar will correct the steering geometry after a lift.

my advice, and the best advice, is to do both.
I think you missed my point entirely. IMHO, there is no problem on the steering geometry with a 4" lift. If you want to go ahead and use a DPA, feel free. However the point is if you use a DPA you must also relocate the TB in order to keep the drag link and DPA parallel to prevent bumpsteer. If you want to use an adjustable TB as well, go right ahead as that's not the issue.
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Old 03-27-2007, 10:53 PM   #8
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Thumbs up

Gentlemen, thank you all for the vast and controversial advice. My vibrations were due mostly to unbalanced tires. I have BFG Mud Terrains and the placed that installed them told me they did not need balancing because they were "too big." Anyhow, the tires were so badly balanced that it took 225 grams of weights for the worst one and 85 grams for the best one. I still have the OEM track bar (drilled over 3/4" towards the driver side) and the DPA provided with the lift kit. Not for long though. I have decided to go with a heavy duty adjustable track bar and put it back in its original location. I have also purchased a better steering dampner and a skyjacker heavy duty steering tie rod. Last question, and I think I'll get mixed replies again, should I used the stock DPA when I install the new adjustable track bar in its original location? Or should I use the OEM DPA? Is there anyway to test steering geometry other than on the road? Thanks again for all the suggestions and help.
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Old 03-27-2007, 10:56 PM   #9
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If you are not installing a drop trac bar bracket on the frame side then you do not need a drop pitman arm. The stock pitman arm will be perfectly fine for you.
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Old 03-27-2007, 11:31 PM   #10
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If you are not installing a drop trac bar bracket on the frame side then you do not need a drop pitman arm. The stock pitman arm will be perfectly fine for you.
Ditto all that 100%. Even more, installing the DPA on your rig set up as it is would just cause bumpsteer.
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Old 03-28-2007, 01:34 AM   #11
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Last question, and I think I'll get mixed replies again, should I used the stock DPA when I install the new adjustable track bar in its original location? Or should I use the OEM DPA? Is there anyway to test steering geometry other than on the road? Thanks again for all the suggestions and help.
Rather than listening to all of us I would suggest you call one of the numerous companies that employ engineers who design suspensions rather than listening to a bunch of backyard mechanics giving advice based on their limited experience and knowledge on what they believe to be true. Unless you believe they are all in on the dpa conspiracy.

Anyway, call around and make up your own mind, and don't listen to any of us.
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Old 03-28-2007, 01:46 AM   #12
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Rather than listening to all of us I would suggest you call one of the numerous companies that employ engineers who design suspensions rather than listening to a bunch of backyard mechanics giving advice based on their limited experience and knowledge on what they believe to be true. Unless you believe they are all in on the dpa conspiracy.

Anyway, call around and make up your own mind, and don't listen to any of us.

You and I both know that the individuals that design most of the lifts at the companies we support are not engineers. Steering on a solid axle is not that complicated. Also if said people at the lift companies were such valuable purveyors or information then why on earth would they want someone to use the stock trac bar and drill a new hole in the bracket?
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Old 03-28-2007, 07:07 PM   #13
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Not saying every company does. However, when we at MOABJEEPER Magazine are researching or testing products we deal with engineers and employ an engineer ourselves. Otherwise it's like doing seat dyno's on product... worthless!
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Old 03-29-2007, 11:09 AM   #14
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Rather than listening to all of us I would suggest you call one of the numerous companies that employ engineers who design suspensions rather than listening to a bunch of backyard mechanics giving advice based on their limited experience and knowledge on what they believe to be true. Unless you believe they are all in on the dpa conspiracy.

Anyway, call around and make up your own mind, and don't listen to any of us.
You're pretty tough to reason with on this subject. But what we're saying about dropped Pitman arms wasn't born out of the rumor mill as ten years of TJs has produced a lot of experience with this issue.

If you have access to back issues of Jp magazine, check out page 61 of the May 2005 issue that I just stumbled across last night where even it says in an article for TJ owners: "Don't run a dropped Pitman arm unless your lift kit drops the trackbar the same amount, or you'll end up with bumpsteer."

We're not making this stuff up, perhaps you should just accept the collective experience of a lot of Jeepers? Heck even Jp magazine is saying exactly the same thing as we are... and what I've been saying for 8-9 years now since I finally fully understood the geometry issue.
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Old 03-29-2007, 09:19 PM   #15
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I really think that everyone can benefit from Jerry's knowledge. IMO, he has more jeep knowledge and experience than anyone else. Also, he is very gracious with sharing his knowledge and never talks down to anyone. He shows respect to everyone and he has all of my respect.

Take a look around the forum at some of Jerry's posts. You will learn.
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Old 03-29-2007, 10:41 PM   #16
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I really think that everyone can benefit from Jerry's knowledge. IMO, he has more jeep knowledge and experience than anyone else. Also, he is very gracious with sharing his knowledge and never talks down to anyone. He shows respect to everyone and he has all of my respect.

Take a look around the forum at some of Jerry's posts. You will learn.
x2. i agree. this guy knows a ton and i love to say "Jerry has seen 17 dana 35's break"
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Old 03-29-2007, 10:41 PM   #17
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Quote:
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"Don't run a dropped Pitman arm unless your lift kit drops the trackbar the same amount, or you'll end up with bumpsteer."


exactly ... thats what i was trying to say in my posts .... and from previous experience with Moab Man, he knows this better than anyone

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Old 03-30-2007, 01:54 AM   #18
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exactly ... thats what i was trying to say in my posts .... and from previous experience with Moab Man, he knows this better than anyone

Exactly.


Quote:
You're pretty tough to reason with on this subject.
When information is not correct I don't throw in the towel. What affende said above is correct. To just say, as you do, that a drop pitman arm causes bumpsteer is no more correct than saying the new wheels I put on a set of tires caused them to bounce if I didn't get them balanced. Address the whole of the topic and I wouldn't be difficult, but to just say a drop pitman arm causes bumpsteer is incorrect.

Additionally, a stock pitman arms ball joint does not have the range of movement to accomodate a 4" lift flexing out. This not only strains the joint but the gear box as well.
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Old 03-30-2007, 05:03 AM   #19
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.....

Additionally, a stock pitman arms ball joint does not have the range of movement to accomodate a 4" lift flexing out. This not only strains the joint but the gear box as well.
I thought it used a tie rod end not a ball joint?
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Old 03-30-2007, 10:46 AM   #20
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Exactly.



When information is not correct I don't throw in the towel. What affende said above is correct. To just say, as you do, that a drop pitman arm causes bumpsteer is no more correct than saying the new wheels I put on a set of tires caused them to bounce if I didn't get them balanced. Address the whole of the topic and I wouldn't be difficult, but to just say a drop pitman arm causes bumpsteer is incorrect.
Dude you are friggin' impossible. Go back through this thread and show me where I did not explain when a DPA will cause bumpsteer and when one should be installed to avoid bumpsteer.

I NEVER made a flat statement that installing a DPA always causes bumpsteer and you know it. WTF is your issue with trying to twist what someone has repeatedly said into something they did NOT say?
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Old 03-30-2007, 09:33 PM   #21
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I thought it used a tie rod end not a ball joint?

the only difference, really, is a TRE is aballjoint with a threaded shank on it
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Old 03-30-2007, 09:37 PM   #22
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I NEVER made a flat statement that installing a DPA always causes bumpsteer and you know it. WTF is your issue with trying to twist what someone has repeatedly said into something they did NOT say?

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Ditto all that 100%. Even more, installing the DPA on your rig set up as it is would just cause bumpsteer.
moab man and i arent saying that it wont cause bump steer, what we are saying is that a DPA and a lengthened / adjustable trackbar should both be installed on any lifted jeep in order to correct 1) the incorrect steering geometry and 2) the lateral axle placement

if you do one or the other, then you will get bumpsteer as the dragrod and the trackbar will no longer be parallel.

if you dont install either, then the steering is working out of its angle range is being stressed and the tracbar is acutally pulling the axle to the driver side (towards the frame mount)

if you install both, as we both have extensive experience with and as we are both saying, they all of the potential, and realistic problem, are fixed.
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Old 03-31-2007, 12:29 AM   #23
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Quote:
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I NEVER made a flat statement that installing a DPA always causes bumpsteer and you know it. WTF is your issue with trying to twist what someone has repeatedly said into something they did NOT say?



Quote:
Originally Posted by Jerry Bransford
Ditto all that 100%. Even more, installing the DPA on your rig set up as it is would just cause bumpsteer.


The second quote answers your first quote.
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Old 03-31-2007, 12:35 AM   #24
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If you are not installing a drop trac bar bracket on the frame side then you do not need a drop pitman arm. The stock pitman arm will be perfectly fine for you.
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Ditto all that 100%. Even more, installing the DPA on your rig set up as it is would just cause bumpsteer.
If you are going to quote someone out of context you might as well get it right and put both statements there instead of just trying to make someone look dumb, since Jerry was quoting my post with his reply and agreeing to what I had said.
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Old 03-31-2007, 12:57 AM   #25
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Jerry did not say installing a DPA causes bumpsteer. he stated that installing one " on your rig set up as it is" would. He is correct. If you don't add a TB drop bracket as well, a DPA will cause bumpsteer.

If you take two parallel lines drop one end of one line 1" you must also drop the same end of the other line 1" to keep them parallel. You guys keep talking about geometry but don't understand that?

If the DL and TB are not parallel, the cycling of the suspension causes the axle/steering to shift hence bumpsteer.
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Old 03-31-2007, 03:33 AM   #26
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I thought it used a tie rod end not a ball joint?
It is a tie rod end. What I was getting at is the actual joint itself is a ball joint that does not articulate far enough for up to 6" of lift with a stock setup.


It is amazing how mind numbing this is. I have learned from reading it here, and hearing it directly from others on this board, that you don't argue with certain people because if they say it then it must be true.

So I give, on this forum dpa are crap and suspensions are not hindered by running a stock pitman arm with up to 6" of lift. To think of all the time we've wasted. Silly engineers thinking they know what they are doing.

Respond if you want, but I'm done beating my head against this wall. For those that warned me... I'm a slow learner but in the end you all were right.
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Old 03-31-2007, 09:28 AM   #27
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I think there seems to be a communication problem here. No one is saying that DPA's are crap. I stated that "anything above 6" usually uses a DPA." Some manufacturers do at anything above 4". Most do not at 4" or below. The OP is at 4". Is a DPA necessary in his instance? I don't feel it is. Can he use one? Absolutely. As long as he does a drop TB bracket as well. I think DPA's are great. They are just not necessary in many instances and often do more harm then good if you don't take into consideration the changes that have been made by lowering the drag link and accounting for it by dropping the TB as well.

I don't think you're views on a DPA are necessarily wrong, I was arguing because you keep misinterpreting/misrepresenting what people have been saying.
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Old 03-31-2007, 09:36 AM   #28
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Obviously you are both very experienced and have different opinions. Both of you guys know more about jeeps than most of us ever will and yall are both greatly appreciated here

Both of you are respected here and the rest just don't matter.
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Old 03-31-2007, 10:48 AM   #29
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i believe this is what you want to see, (buddy in washington new steering setup) correct if im wrong please.


my steering looks like this and i have no issues and no DPA.
mines a little off.
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Old 03-31-2007, 11:37 AM   #30
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"Jerry has seen 17 dana 35's break"
Whats with the smily face you're suppose to be sad when stuff needed brakes lol

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