Adjustable Rear Track Bar needed?

[Jms1]

Sorry if this is a simple question, have not been on here in a few years. My 2022 Badlands has Bilstein 6100's with 34.0 tires, just a bit over stock height. I noticed that the rear axle is shifted to the passenger side about 3/4" on flat ground. How close to center should this be? Would it be beneficial to install an adjustable rear track bar and center it up? If so what brand would you recommend? I am not up to speed with recent Bronco parts, some seem very cheap and poor quality. Thank you for any expertise.

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[Brian_B]

Probably just need the trac bar relocation bracket rather than an entire new bar

https://www.bronco6g.com/forum/threads/rear-trac-rod-relocation-bracket-enlighten-me.81416/

 

[Oldhippie]

It should be centered…3/4” is a lot…a relocation bracket may work and a good addition after a lift…but why is it off center?…I just got a Core track bar (along with control arms but haven’t installed yet) because mine has been off a little after lift (have relocation bracket)…probably overkill…

 

[Draughon]

This might help explain things:

 

[Jms1]

It should be centered…3/4” is a lot…a relocation bracket may work and a good addition after a lift…but why is it off center?…I just got a Core track bar (along with control arms but haven’t installed yet) because mine has been off a little after lift (have relocation bracket)…probably overkill…

The part i find out of sorts is the axle is 3/4" to the passenger side direction. The track bar is not at a crazy angle in part because I am only lifted one inch in the rear. I tried a RockJock relocation bracket but it moved the bar up to far. My OEM track bar is 44" center to center. Correct me if I am wrong but I need to shorten that length to center the axle. Does the Badlands Bronco start with the axle shifted to the passenger side from the factory? I have never had any issues, I just happen to notice this.

 

[Oldhippie]

The part i find out of sorts is the axle is 3/4" to the passenger side direction. The track bar is not at a crazy angle in part because I am only lifted one inch in the rear. I tried a RockJock relocation bracket but it moved the bar up to far. My OEM track bar is 44" center to center. Correct me if I am wrong but I need to shorten that length to center the axle. Does the Badlands Bronco start with the axle shifted to the passenger side from the factory? I have never had any issues, I just happen to notice this.


If that is actually the case I would get it checked out by a good frame/alinement shop before throwing money/parts at it…good luck!

 

[Jms1]

Will have it checked tomorrow. Thanks

 

[87-Z28]

Lateral movement from OEM panhbar is fairly small, if setup properly.

For a rear motion ratio of 1.1 and a shock travel of 10” you get a maximum vertical wheel travel of 11”.

lateral movement from Panhard bar can be calculated as:

L - Vt / [ tan(asin(Vt/L)) ]

L is Panhard length
Vt is vertical travel

For a balanced Panhard set up, ie, horizontal bar at ride height with shock equilibrium near mid stroke. Max lateral movement is only, 44-5.5/(tan(asin(5.5/44)))=0.35 inches. Very small number. This would be the desired design criteria.

worst case Panhard set up, ie, all lateral movement in only one direction, rebound. This occurs when bar is level at full jounce and thus has some “large” angle at ride height. Maybe a 5” drop or so, asin(5/44)*(180/3.14)=6.5 degrees. Max lateral movement now becomes, 44-11/(tan(asin(11/44)))=1.4 inches. Much larger than having an optimized panhard angle at ride height.

highly nonlinear behavior due to the circular motion of the Panhard. Lateral movement can be minimized by getting Panhard setup properly.

you can put the rear end on Jack stands and measure the perpendicular vertical distance from passenger side Panhard/axle mount to horizontal reference line from Panhard/frame mount. Drop rear end To ground and do this again at ride height. The difference of those two numbers is the vertical wheel travel in rebound. You can also measure Panhard angle from horizontal at ride height, asin(x/L). Where x is vertical distance to horizontal. You can then determine maximum axle lateral movement you will see at full rebound.

if you are not lifted very high, using typical length coilovers and not using excessive spring preload, then your Panhard angle should be fairly small, <3 degrees. Maybe a two inch drop at most, asin(2/44)*(180/3.14)=2.6 degrees. I doubt your Panhard setup will cause 0.75” lateral axle shift. Likely your axle wasn’t centered to begin with or your links/frame alignment is off.

Either way, I would cycle the rear suspension, in full rebound anyway, and convince yourself the Panhard arc motion is reasonable. Getting the axle centered with an adjustable Panhard is easy enough, but I would also evaluate how the suspension is cycling. An opportunity to learn and think about the kinematics anyway.

keep in mind, the optimal oem Panhard setup produces less than 0.5” lateral movement. Measuring lengths from imaginary lines can be challenging and easily have >0.25” errors.

the easiest starting point is measuring you Panhard angle at ride height.

 

[dgorsett]

Lateral movement from OEM panhbar is fairly small, if setup properly.

For a rear motion ratio of 1.1 and a shock travel of 10” you get a maximum vertical wheel travel of 11”.

lateral movement from Panhard bar can be calculated as:

L - Vt / [ tan(asin(Vt/L)) ]

L is Panhard length
Vt is vertical travel

For a balanced Panhard set up, ie, horizontal bar at ride height with shock equilibrium near mid stroke. Max lateral movement is only, 44-5.5/(tan(asin(5.5/44)))=0.35 inches. Very small number. This would be the desired design criteria.

worst case Panhard set up, ie, all lateral movement in only one direction, rebound. This occurs when bar is level at full jounce and thus has some “large” angle at ride height. Maybe a 5” drop or so, asin(5/44)*(180/3.14)=6.5 degrees. Max lateral movement now becomes, 44-11/(tan(asin(11/44)))=1.4 inches. Much larger than having an optimized panhard angle at ride height.

highly nonlinear behavior due to the circular motion of the Panhard. Lateral movement can be minimized by getting Panhard setup properly.

you can put the rear end on Jack stands and measure the perpendicular vertical distance from passenger side Panhard/axle mount to horizontal reference line from Panhard/frame mount. Drop rear end To ground and do this again at ride height. The difference of those two numbers is the vertical wheel travel in rebound. You can also measure Panhard angle from horizontal at ride height, asin(x/L). Where x is vertical distance to horizontal. You can then determine maximum axle lateral movement you will see at full rebound.

if you are not lifted very high, using typical length coilovers and not using excessive spring preload, then your Panhard angle should be fairly small, <3 degrees. Maybe a two inch drop at most, asin(2/44)*(180/3.14)=2.6 degrees. I doubt your Panhard setup will cause 0.75” lateral axle shift. Likely your axle wasn’t centered to begin with or your links/frame alignment is off.

Either way, I would cycle the rear suspension, in full rebound anyway, and convince yourself the Panhard arc motion is reasonable. Getting the axle centered with an adjustable Panhard is easy enough, but I would also evaluate how the suspension is cycling. An opportunity to learn and think about the kinematics anyway.

keep in mind, the optimal oem Panhard setup produces less than 0.5” lateral movement. Measuring lengths from imaginary lines can be challenging and easily have >0.25” errors.

the easiest starting point is measuring you Panhard angle at ride height.

I never could understand trig, so thanks for this. I did a small (1.7") lift on my Bronco and not really concerned about movement at full travel but curious about bump steer. My panhard was nearly horizontal originally and now has a slight incline. By using stupid man's trig (Pythagoras), on such a small portion of an arc, I decided lateral movement over road imperfections was minimal and stayed with stock. I do notice some bump steer, but don't know if it's caused by this.

 

[87-Z28]

I never could understand trig, so thanks for this. I did a small (1.7") lift on my Bronco and not really concerned about movement at full travel but curious about bump steer. My panhard was nearly horizontal originally and now has a slight incline. By using stupid man's trig (Pythagoras), on such a small portion of an arc, I decided lateral movement over road imperfections was minimal and stayed with stock. I do notice some bump steer, but don't know if it's caused by this.

lateral movements near a horizontal bar for small angles are absolutely small. Hard to get more than 1/2” but likely smaller. Big bumps where suspension cycles a few inches maybe 0.5” or so.

a better question is can 0.5” of lateral movement effect the tracking of rear with respect to front wheels and noticeably alter steering inputs??? I suspect it depends on bump size, speed, and current steering angles.

We have all felt this phenomenon. All that can be done at the rear to minimize this is have a perfectly horizontal bar at ride height. That should most definitely alleviate minor bump steer. Increasing panhard length will also reduce lateral travel but harder to implement.

my bar is fairly level and I don’t really notice it often. I am however fairly forgiving with such things and don’t bomb around like a formula one car. To me this is all a bit overblown. But I do understand those that want increased steering performance.

 

[dgorsett]

I notice it on one local road with unlevel manholes, but I'll bet the axle doesn't shift 1/4 ". Never notice it off road. With my little 1.7" lift a relo bracket would probably shift it the other way

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