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Old 11-18-2020, 08:49 AM   #1
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Track bar thoughts. Good idea or not?

I can't see how a track bar does anything good for a leaf spring suspension and possibly harm. A track bar attached to the frame and the axle has to move in a circle. A leaf spring mounted axle moves vertical, up and down. A track bar can't follow the vertical movement of the axle without increasing in length (it can't) or pulling the axel toward the side of the frame where the track bar attaches. If the track bar is intended to keep the axle from moving of center it's failing.
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Old 11-18-2020, 09:07 AM   #2
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Except that's not how a track bar works. At least not in a Class C application like the Super Steer unit. It's designed to limit LATERAL movement of the axle in relation to the frame.

I would agree that IN GENERAL, a leaf sprung suspension would not benefit greatly from a track bar. Note that I have removed BOTH track bars from my 1994 Jeep YJ to help the suspension gain a bit more travel and avoid the very binding you describe. But in that particular application, I WANT more movement as it's better for off-road suspension flexibility. On that particular Jeep model, they were specifically installed to LIMIT suspension travel due to fear of rollover.

On my motorhome, I want to LIMIT that axle movement as much as possible to further "stabilize" the axle under the chassis. Thus, the track bar.

A few members here have installed them on Motorhomes, and all are VERY satisfied.
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Old 11-18-2020, 11:31 AM   #3
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I agree, the intention is to limit lateral movement. It does that perfectly when the the suspension isn't moving up or down past it's normal position. Again you are right in your jeep example. They will limit suspension travel because the bar can't get longer to follow the up or down path of the axle. Raise the position of the axle in my diagram. The track bar, being a fixed radius, can't follow the path of the axle. It either restricts the up and down motion of the axle or pulls the axle toward the frame.
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Old 11-18-2020, 11:42 AM   #4
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Again, it is DESIGNED to limit movement. Lateral movement to be specific. Sure, it will somewhat limit up/down movement as well (which is also a good thing in most cases and further helps to reduce body roll), but it's the lateral movement that we're looking to control, and the track bar does a great job of that, specifically in a motorhome application.

Reference video:

https://youtu.be/PXVACs-BW9s

Moreover, MANY people have installed track bars on their rigs with GREAT success. So to assert that "track bar is useless" is not very well informed.
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Old 11-18-2020, 11:58 AM   #5
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Great way to shut down an intelligent debate!
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Old 11-18-2020, 03:24 PM   #6
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I had no intention of "shutting down an intelligent debate". But there has to be an intelligent debate to be had first; your opening remark was your conclusion. Anything I say is unlikely to change your mind.

You're absolutely right that suspension binding can occur with a track bar and leaf sprung suspension. You simply can't cheat physics.

Question: Have you personally ever installed a track bar on a motorhome? Did you drive the vehicle immediately before and after the installation? Have you spoken to someone who has? Full disclosure: I have not installed a track bar on my motorhome (yet), but I have read MANY accounts from users who have, and they are VERY happy with the improvement. I pretty much don't do anything without stupid amounts of research first, and I've been researching this ahead of a likely install.

Where you're wrong is your assertion that a track bar is "useless" in this application. It's proven NOT to be useless, and in fact LOTS of people report the installation of a track bar in an F-53 or E-450 chassis application on a motorhome has been immensely helpful to handling and tracking. OEMs have even begun installing them, and no OEM that I know of would spend an extra penny on installing something that had no benefit. They often don't even install things that have significant KNOWN benefits; gotta pinch those pennies.

The amount of vertical movement that MAY be inhibited by a track bar in this application is not significant enough to cause harmful binding. The axle is still free to travel vertically nearly the same as without the track bar. The length of the bar, and the distance of travel as well as the bushings on the ends of the bar help reduce that binding referenced in your diagram. And look closely at the apex of the curve relative to the axle's line of travel; the axle doesn't travel far enough along the curve to cause significant binding. And as I said, any binding that IS created simply adds to the benefit.

Body roll and suspension movement is a real problem on a vehicle that's loaded at or above GVWR pretty much at all times. The high center of gravity of a motorhome just exacerbates the problems. Anything a user can do to limit or control that will provide improvement in handling.

Back to my Jeep example: LOTS of YJ guys run WITH their track bars, even with leaf-sprung suspension. Why? Because they don't need the suspension travel required for off-roading, and the track bar, in fact, gives the Jeep better on-road manners by limiting body roll, especially in turns. This is partially provided by the very binding you reference in your diagram. In addition, the effects of other worn suspension components can be mitigated or even hidden completely with track bars installed. I can tell you from first hand experience that I have to take turns slower in my Jeep now that I've removed the track bars. I'm well aware of this change in handling, and am willing to accept that. My Jeep isn't a race car, I don't need to take corners fast, and I'm willing to accept additional body roll to have a more freely moving suspension. At least in THAT particular application. YMMV.
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Old 11-19-2020, 06:35 AM   #7
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Thanks Bob. I appreciate the thought you have put into your response. It's clear to me you understand the application and function of a track bar. My initial post was intended to spark debate and analysis. I hadn't considered it might offend people who have purchased a track bar. My opening statement should have been, "there are better options, such as a sway bar".

In my opinion a sway bar is a better choice because it is intended to directly address the handling and ride problem inherent in a motorhome. I believe excessive sway is, at least, uncomfortable and dangerous when extreme. The roads I drive on often have a lot of undulations on the ditch side that causes a lot of sway and causes what I call "sway steer". A dip on the passenger side of the road causes the coach to pull to the right. Much like leaning a motorcycle.

A track bar likely helps with sway and handling, as a secondary effect, by limiting suspension travel. I suspect this is what users experience. The limit to suspension travel may not be noticeable when driven on major roads. Spending the most of my driving hours on secondary roads I appreciate suspension travel.

Manufacturers make what customers ask for. Many people purchase performance mods based on claims of increased horse power but don't notice it works at wide open throttle but kills street drivability. Many buy premium gasoline expecting more power without other modifications but swear it works. Small displacement engines with huge exhaust systems make more HP and noise at WOT but kill throttle response and torque.

I have never installed a trackbar on a motor home. Sway bar? Yes.

During the past 45 years I have built new fire trucks and repowered, rebuilt, and restored old fire trucks. Have also built utility trucks such as digger derricks and bucket trucks. My background in physics, geometry, and chemistry causes me to question ideas, maybe a little OCD.
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Old 11-19-2020, 07:16 AM   #8
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All 3 of the 7.3 powered super duty's I have owned had both a track bar and a sway bar. Not an engineer, but I did stay at a holiday inn express last night.
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Old 11-19-2020, 09:21 AM   #9
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Hi all- Bob your analysis and description of the trac bar function is very good. Another aspect or benefit of the trac bar is it compensates for wear in the rear spring components, and rubber spring eye bushings and more importantly they minimize the "twist" the rear springs undergo when hit with the pull of the vehicle they are carrying. I have installed store bought, and have built custom trac bars, and if you are trying to minimize lateral body shift/roll , they are a good way to go. Red, technically you are correct, there will be push and pull on the rear differential with a trac bar, but less than the vehicle would do on its own without the bar, and the trac will do so in a more consistent and predicable manner.
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Old 11-19-2020, 09:25 AM   #10
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Redshift, if as you claim, your post was intended to spark debate and analysis, you did not make that in the least bit clear. Also, you may have added that your opinion that a sway bar does a better job at correcting the problem a track bar is intended to correct in your original post. I'm not offended at all by the initiation of discussion or debate. And like you, I am VERY critical of add on components as well as their side effects and unintended consequences. What offends me is when people make a blanket statement as you did with no direct experience, then fail to adequately defend their position. If you had installed a track bar and it did nothing for you, that may be different. That being said, I only have my experience, research and observations to rely on. If your statement had gone unchallenged, another person may have stumbled upon it in their own research and gotten the wrong idea.

In my opinion, the optimal install on a motorhome will include an upgraded sway bar (such as the VERY popular product offered by Hellwig) AND a track bar. Incidentally, this is what I intend to do. As part of J-Ride Plus, my rig includes an upgraded sway bar, but I think we can do better and am seriously considering a track bar.

I appreciate your experience with heavy duty, commercial level builds, and the physics aspect of your argument is sound, but it seems you're missing something critical in this particular application. The track bar in this case is quite long. As the length of the track bar increases, the arc that causes binding smooths out along the vertical travel of the axle. Further, if the frame-based attachment point is more parallel to the axle, the effects of the push/pull on the axle are further reduced, or more accurately, more equalized in the upward/downward travel of the axle.

Add into the mix other suspension components that were marginal when the rig left the production line and have worn over time, and the problems get worse. The track bar helps to mitigate that additional flex introduced as other components wear over time. It helps the frame and the axle move TOGETHER instead of the frame being allowed to move laterally in relation to the axle, especially during turns.

I would estimate that IF there is any binding introduced as a result of the track bar, the axle is not allowed to travel far enough naturally for that to become a problem. Said another way; the axle cannot travel far enough vertically to introduce a problematic binding effect. It would be interesting to see what the lateral forces on the ends of the track bar are at full suspension droop or stuff. This would definitively answer our question as to the presence of any binding that would limit axle travel.

I will SERIOUSLY consider taking before and after measurements if/when I install my track bar. I think I can get axle droop measurements pretty easily? But axle stuff measurements might be a bit more difficult? My goal would be ascertain if the track bar affects the vertical travel of the axle in any way (identify potential binding).

Bottom line is that I totally get why the physics of the situation lend to a track bar being ineffective. The diagram in your original post says it all. And as I said before, you simply can't cheat physics. But they work. They're proven to work. People who have installed them swear by them. How can that be?
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Old 11-19-2020, 11:57 AM   #11
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Bob, I think people report that track bars help because they probably do. Reduction in sway is a lot more noticeable than reduced suspension travel.
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Old 11-19-2020, 12:23 PM   #12
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snip....
Quote:
Originally Posted by redshift View Post
My opening statement should have been, "there are better options, such as a sway bar".
We have the ability to change your thread title to something else, if you wish. Let me know if you'd like to change it. Just one more service the Site Team has to offer!
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Old 11-19-2020, 12:34 PM   #13
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Thanks, maybe it's best to delete it completely. kevin
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Old 11-19-2020, 12:45 PM   #14
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Quote:
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Thanks, maybe it's best to delete it completely. kevin
The thread needs to have a title, so I've changed it to "Track bar thoughts. Good idea or not?" Thanks for agreeing to that.
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Old 11-19-2020, 12:47 PM   #15
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Works for me! Thanks, kevin
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Old 11-19-2020, 01:12 PM   #16
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You're very welcome Kevin. Happy trails!
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Old 11-19-2020, 01:32 PM   #17
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PERFECT! Thank you JFlightRisk!

I don't think the thread should be deleted, there are some VERY good points on both sides, and some healthy discussion!

I know it's helped me for sure!
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Old 11-19-2020, 01:55 PM   #18
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So then we should build on the discussion I think?

I agree completely that a sway bar in the rear is all but an essential upgrade (and it needs to be an aftermarket upgrade, not the Ford OEM part as those are pretty much useless). I also believe that a track bar has an added and distinctly separate benefit. It would be amazing if we could hear from someone who has installed BOTH components incrementally.

I expect the sway bar to provide an immediate and significant benefit (and have observed this through others' installations, and my own on the front end). I would further expect another incremental benefit after installation of a track bar. I'm curious the level of those incremental benefits? Was there a corresponding change in ride quality from the up/down axle travel stand point? If suspension travel is limited, does that really matter?

Side thought: I think any suspension binding would be isolated at the "margins". If you lose an inch at full droop, does that really make a difference? Same question at full stuff? Just going down the road, you shouldn't notice a decrease in suspension travel. And if you're hitting your bump stops so much that you would notice, maybe something else is going on?

As far as I know, there are only 2 active members here that have installed a track bar and talked about it on this forum. I've looked for discussions, conducted searches, and even solicited feedback from members who have done it. But I don't think anyone has installed a sway bar, then measured, then installed track bar, then measured again?

For MY part, I will take measurements when I install mine, but it will hardly be scientific. And I already have the sway bar, and always have, so I have no comparison between the installation of BOTH components. The other problem is it may be a VERY long time before I ever get to that installation; I've got a LONG list of mods to my Jeeps, my boat, and elsewhere on my MH that are higher priority at this time, and like most others, I'm on a limited budget unfortunately. So I'm afraid I won't be much help for the before/after discussion...
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Old 11-19-2020, 02:35 PM   #19
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Out of curiosity I calculated what would happen through the range of the suspension travel based on the potential for 4 inch maximum compression (distance from the axle to the bump stop). If the suspension compresses 2 inches the track bar will try to pull the axle toward the frame by 1/16 inch. That little can probably be absorbed in the bushings if there are any, not so if the bar has Hiem joints. At 4 inches of compression the differential is pulled only 1/4" toward the frame. Doesn't seem significant in the short term. To illustrate the difference in operation between a track bar and a sway bar imagine driving on a ride hand cloverleaf. The track bar is trying to keep the coach aligned with the axle, the coach leans into the curve but doesn't rock back when the curve is over. A sway bar tries to keep the coach level with the horizon and the suspension following the road.
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Old 11-25-2020, 02:17 PM   #20
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If you're trying to keep an axle centered under a vehicle probably the best way is with Watt's linkage. The first one that came up in a quick google search is https://www.monacowatts.com/
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