How critical is drag link geometry

[oldiron]

How important is keeping the drag link parallel to the track bar, OR what are the driving issues that will come from this? I've installed the drop track bar bracket without a drop pitman arm, and the two are not on a parallel plane. Steering is ok but feels a little off/twitchy. Is that a symptom?
I'm still on the '72 with 3.5"lift, power steering, new everything.
Greg

 

[73azbronco]

Off twitchy could be simple like toe in, tire pressure, or shocks.

Unparallel adds variable issues during flex or cornering/turning. Takes more or less to turn or variable amounts as suspension is flexed.

 

[AZ73]

Death Wobble. Take it up to speed and see what happens.

 

[ohpoo2]

They need to be parallel or will be twitchy. DirtDonk helped me out with mine very helpful. Good luck.

 

[B RON CO]

Hi, when the two bars are parallel the suspension travel is supposed to cause the drag link and trac bar to travel in similar arcs as the spring compresses and rebounds. If the arcs are way different because the two bars are not parallel the drag link will yank and pull tires away from where you are steering. This is called bump steer. That is why it is so important to plan and set up your front end properly. You are making big changes to the way Ford designed it. You should plan the bar angles and the castor angle so your new design has good manners. Good luck

 

[oldiron]

Death Wobble. Take it up to speed and see what happens.

Took it out and ran it up to 70...no wobble at all.
Alignment was done earlier today.

 

[B RON CO]

Hi, if you can post the alignment numbers you will get a lot more information. Good luck

 

[oldiron]

I didnt get a printout of the alignment specs.

 

[Broncobowsher]

Not necessarily parallel, but the arc of travel has to match. Being a shallow angle can fix things that being parallel can't (track bar riser, steering over, drop bracket, drop pitman arm).

If you lock the tie rod to the axle (scrap metal, vice grips, C-clamp, whatever it takes) and bounce the front suspension (remove front shocks helps). Watch the steering wheel. If you see if cycling back and forth, you have bump steer. Changing the angles can fix this.

But that isn't all of it. Even without bumpsteer you can still have a funky front suspension. If the angles are steep you will get a weird body yaw action when the front suspension cycles. The axle shifting side to side will actually go in a straight line and the body will be what is shifting. The softer the springs, the more sensitive this will be.

 

[oldiron]

Well I've done some more driving and maybe I have a more accurate description of what I'm talking about. At highway speeds it seems fine, no wobble, tracks straight, etc. At low speeds on windy country roads it feels a little loose. (not wandering all over the place but not tight either) And it seems slow to recenter after a turn. I had a concern with this steering box when I bought the bronco (p.o. had run the "adjusting" screw all the way in)
Maybe I'm looking in the wrong place? But I wanted to see what you guys thought about the drag link not being parallel.
Greg

 

[nvrstuk]

Knowing what your caster was on the recent alignment would be helpful in diagnosing your steering issue.

 

[DirtDonk]

Yes, you need them as parallel and as close to the same length as you can get them. Period.

It's how Ford designed it, and how you should try to keep it after other modifications have changed the relationship.
I'm wondering why you would make a change that is not recommended in the first place? It sounds like you're at least somewhat aware of the issue, because you asked about the need for keeping them parallel.

By that I mean you are going against all the recommendations by using a trackbar drop and not a pitman arm to match it. You've added part to bring one link back closer to factory spec (the drop bracket) but have left the draglink in a completely non-stock orientation.
With it's new higher angle you have very likely also pushed the steering box off-center. That last bit alone will often contribute to funky steering. Add to it the steeper angle and you have a real recipe. Then add the out-of-parallel aspect, and at least on paper you have a poor handling Ford.

If you bought the bracket from us and nobody mentioned it, I apologize for the lapse. Even though when someone buys just one of those items it's usually because they only need to replace one and already have the other, or don't need one because of other modifications. But we should still ask.

Is the steering setup custom? Or is there a reason you did not want to use a dropped pitman arm?
One of the few exceptions to the general rule of using both items together, or not at all, is if you've custom modified your steering system. Non-stock steering box that relocates the pitman arm, or non-stock tie-rod location (such as TRO) or other mod that changes where things sit in relation to each other.

Things that help achieve better steering are:
1. Trackbar and draglink parallel.
2. Trackbar and draglink same length.
3. Keeping the overall angles as low as possible.
4. Making sure that the steering box is in it's on-center position when at ride-height.
5. Air pressures in the tires. Don't go by the sidewall rating. Go by testing.
6. Tire age, condition and style.
7. Alignment. Here's another area that can benefit you from changing the original specifications.
8. Something loose. Trackbar bushings and/or mounting points, cracked frames behind the box, worn or improperly adjusted wheel bearings, loose wheels, cracked wheels, etc.

If not using a dropped arm was just a cost savings thing, I would recommend saving it elsewhere and adding a pitman arm.

Paul

 

[oldiron]

That's the definitive answer I was looking for. I have read (somewhere) that the drop pitman was a "maybe" item based on need. I.E. some will need it, some wont. It appears that I fall into the will category. Everything else is new on the front, wheels,tires,bearings,bushings,seals,tie rod,drag link, etc. I'll order the pitman arm and go from there.
Thanks for the replies. Project "daily driver" is coming together nicely.
Greg

 

[DirtDonk]

Ok, I see what happened. The "some need it, some don't" thing is based on the amount of lift. But not whether to use only one or both items.
So your 2.5" could have gone either way by those standards, but in the "both or neither" category.
Whenever you drop one, you need to drop the other the same amount. That part does not change under normal conditions.
As mentioned, there are exceptions, but they are rare and dependent mostly on other modifications to make up for it.

The 2.5" lifts seem to be the cutoff for dropping them, nor not dropping them. But you are still hurting your angles even with that low of a lift.
My opinion differs, in that I say if you're finicky at all about how your EB handles and steers on the street, you need to correct the steering linkage for anything over 2" of lift. Or if you're into fabrication for the fun of it, you could build drop brackets and pitman arms for just 1" of lift if you wanted to. Overkill? A little maybe, but not without precedent.
If you drive your rig regularly, and have most other things pretty well dialed in, you can definitely feel the difference between stock and 2.5" of lift without the steering correction.
If you have other issues going on at the same time though, you might not feel the slight change in steering angles due to all the other dynamics at play.
And even though the drops are sort of designed around 3" of lift, they're not going to harm anything by over-compensating slightly. Might even make it better than original by keeping the angles low.

Even lower than stock is not automatically bad. Perfectly parallel to the ground is one optimum, on paper at least. But in the real world if you have it perfectly level (parallel to the tie-rod and ground) you could have interference issues with tie-rod deflection under load bringing it too close for comfort to the draglink and pitman arm. So slightly up, like Ford designed, is what we typically keep.

I believe that at least part of the reason for the 3-inch and higher recommendation is historically just trying to save some money and time. And back then too, not as many cared about how their slightly higher than stock Bronco with small tires handled anyway.
After all, it wasn't "that bad" anyway.

Paul

 

[oldiron]

Thanks Paul:
Since this build is aimed toward being a daily driver, street manners are high on the priority list. I'll install the drop pitman as suggested, since I have around 3.5 inches of lift. You mentioned other dynamics being involved in the mix.....I certainly have those, but am wading through them and making corrections as I find them, i.e. '72 EB w/ '73 power steering, lots of p.o. scary modifications...you get the idea.
Thanks again for the replies.
Greg