TRACKBAR, anyone here run one?

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Agent_Orange

Agent_Orange

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I was posting under another thread and the point of that thread changed, so I decided to create a new thread.


Does anyone run a track bar on their rear end? if so what changes did it produce? and pics!
 
Your quote from the other thread:

"Is a Track Bar really necessary for a solid axle suspension with leaf springs? Don't the leaf springs themselves keep the axle centered? or am I miss understanding the effect of the track bar.

At this point, maybe this is a conversation for a different thread....."



I don't know if my opinion is correct, as I don't run a track bar, but here is why I think they are necessary for performance type driving, auto cross, etc.

The "solid axel" you referred to above is 'floating' around a lot when hard driving, power sliding, and making similar hard cornering. There is a lot of flex in your leaf springs, that is what they are designed to do: flex. But think of what happens in a hard corner; the centrifugal force of the corner makes the body want to fly off the road, but the sticky tires hold it as much as possible. Meanwhile your leaf springs are flexing horizontally due to the G-force of the corner. Now your path ahead turns the opposite direction which requires quick, precise steering. The rear end without a track bar is basically slamming around back there, side to side, fouling your handling.

A track bar prevents the side to side movement of the rear axel under your car, while not hindering the normal up / down movement for a better tuned suspension and handling.
 
With 215/60's on cop cars bolted to a Ford Ranger Axle I get tire rub in hard corners, so I've got one on The List.
Some sort of lateral control is worth doing if the rear suspension exhibits a lot of lateral compliance. I'm first going to address the spring bushings as I'm reasonably sure that they are originals. If that doesn't tighten up the rear enough then I'll have to decide on panhard bar, Watts Link, or WOB Link. Panhard is the easiest, but also forces the most lateral displacement relative to suspension travel. Progressively the Watts and the WOB have less forced displacement, but are also progressively more complicated to build.
 
The above is correct; a normal leaf spring assmebly will twist a bit sideways under hard cornering, particularly at the very front and rear ends where it tapers down to one leaf. A thicker mono-leaf will resist this better as it does not taper down. Additionally, the shackles are another source of sideways motion. The panhard rod (track bar) is not essential for a leaf car as it is for a 4 link, as the springs will eventually tigthen up and stop the sideways motion. But for consistency and axle stability, it willl make a great improvement.

Consider this from Sam Posey who drove one of the Trans-Am Challengers fielded by Chrysler: " It was better, but stiffening the frame exacerbated the car’s other weakness: the geometry of the rear suspension. As I braked for certain turns, the rear brakes locked up, causing the axle assembly to jump from side to side, leaving skid marks on the track. All I could do was to brake gently, which of course let anyone following me go right by." Straight from the horse's mouth.....

There is another critical fuction of the track bar if you are really engineering for handling. It allows you move the rear roll center up and down and thus change the roll axis of the car, which can be used to hlep tune understeer/oversteer. With the standard leaf spring setup, the roll center is cannot be moved without changing shackles or re-arching leafs, and is usually higher than desired. If you use rather loose spring bushings in the rear springs and hard bushing or heim joints in the panhard rod, the panhard rod takes over all of the side-to-side locating function and the roll center is determined by the panhard rod settings, not the leaf spring connections to the chassis.

It is pretty easy to build a plate for the axle connection end of the panhard rod; it can just replace the under-spring plate for the leaf spring on one side. The chassis end connection of the rod takes some fabrication and need to spread the load along thr frame rail a bit. If you can find Fred Puhns "How to Make Your Car Handle" book, look at the photos on page 153 of panhard rod mounts on a leaf-sprung car.
 
nm9stheham said:
The above is correct; a normal leaf spring assmebly will twist a bit sideways under hard cornering, particularly at the very front and rear ends where it tapers down to one leaf. A thicker mono-leaf will resist this better as it does not taper down. Additionally, the shackles are another source of sideways motion. The panhard rod (track bar) is not essential for a leaf car as it is for a 4 link, as the springs will eventually tigthen up and stop the sideways motion. But for consistency and axle stability, it willl make a great improvement.

Consider this from Sam Posey who drove one of the Trans-Am Challengers fielded by Chrysler: " It was better, but stiffening the frame exacerbated the car’s other weakness: the geometry of the rear suspension. As I braked for certain turns, the rear brakes locked up, causing the axle assembly to jump from side to side, leaving skid marks on the track. All I could do was to brake gently, which of course let anyone following me go right by." Straight from the horse's mouth.....

There is another critical fuction of the track bar if you are really engineering for handling. It allows you move the rear roll center up and down and thus change the roll axis of the car, which can be used to hlep tune understeer/oversteer. With the standard leaf spring setup, the roll center is cannot be moved without changing shackles or re-arching leafs, and is usually higher than desired. If you use rather loose spring bushings in the rear springs and hard bushing or heim joints in the panhard rod, the panhard rod takes over all of the side-to-side locating function and the roll center is determined by the panhard rod settings, not the leaf spring connections to the chassis.

It is pretty easy to build a plate for the axle connection end of the panhard rod; it can just replace the under-spring plate for the leaf spring on one side. The chassis end connection of the rod takes some fabrication and need to spread the load along thr frame rail a bit. If you can find Fred Puhns "How to Make Your Car Handle" book, look at the photos on page 153 of panhard rod mounts on a leaf-sprung car.
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Only thing is, poseys TA didn't have a rear leaf suspension...... it had a link system simular to a watts link design. The AAR team stuck with the leaf rear factory design, and sam posey himself drove one in practice and commented on how much better the cudas would come off the corners.
 
replicaracer43 said:
Only thing is, poseys TA didn't have a rear leaf suspension...... it had a link system simular to a watts link design. The AAR team stuck with the leaf rear factory design, and sam posey himself drove one in practice and commented on how much better the cudas would come off the corners.
Click to expand...
Well, there he goes lying to me again! Lol
 
Leaf spring suspensions are designed to move up and down vertically with as little lateral movement as they can stand. We all know that there is lateral movement in leaf systems, you cannot get around it.

However, installing a track bar, or more appropriately a Panhard bar, puts a force into the leaf spring suspension that it was not designed to take. By mounting one end of the bar to the frame and the other to the axle, you have now forced the leaf spring suspension to move laterally (like it was not designed to do) with every single oscillation of the rear suspension, because now, the axle end of the Panhard bar along with the axle is travelling in an arc, when it was only designed to travel vertically.

This puts all sorts of forces on leaf spring bushings, brackets and frame mount....wherever you have tied the frame end of the bar that it just was not designed for.

These cars are unibodies with "frames" made outta folded over sheet metal. Over time the frame end of that Panhard bar will likely rip out of the frame where it has been mounted. You can count on leaf spring bushing wear to accelerate as well.

Panhard bars are best suited to link type suspensions where they are designed into the system to begin with.
 
With proper load spreading plates I see no reason why a panhard bar would accelerate the demise of the car. It will need a strut from the frame anchor to the opposite side of the car.

The locator should be made as long as is practical. On my '65 that is roughly 32"-33" long. With 2.5" of up travel in the suspension (more than I actually have) and the bar parallel to the ground the lateral dislocation is less than 1/8"
If the bar at ride height is 1" lower at the axle end than the frame end that dislocation drops to under 0.04"
 
Anyway you slice it a panhard bar describes a radius of a circle, thus forcing the leafs to slightly shift from side to side, "something they do not want to do."

A "perfectly" designed Watts bar would not do this, but I'm not even sure this is exactly possible.

The whole deal is, just how damn stiff do they NEED to be? My old 70 440-6 car handled pretty damn fair, all things considered. It had the factory track pak stuff under it

It would be interesting to see what "the Petty boys" actually did back in those days. Seems to me there's some photos of his 70 upside down............

Unfortunately it's the wrong side LOL

1970RoadrunnerDarlington.jpg
 
RustyRatRod said:
Leaf spring suspensions are designed to move up and down vertically with as little lateral movement as they can stand. We all know that there is lateral movement in leaf systems, you cannot get around it.

However, installing a track bar, or more appropriately a Panhard bar, puts a force into the leaf spring suspension that it was not designed to take. By mounting one end of the bar to the frame and the other to the axle, you have now forced the leaf spring suspension to move laterally (like it was not designed to do) with every single oscillation of the rear suspension, because now, the axle end of the Panhard bar along with the axle is travelling in an arc, when it was only designed to travel vertically.

This puts all sorts of forces on leaf spring bushings, brackets and frame mount....wherever you have tied the frame end of the bar that it just was not designed for.

These cars are unibodies with "frames" made outta folded over sheet metal. Over time the frame end of that Panhard bar will likely rip out of the frame where it has been mounted. You can count on leaf spring bushing wear to accelerate as well.

Panhard bars are best suited to link type suspensions where they are designed into the system to begin with.
Click to expand...

I agree with all the above. Another thing about a mopar leaf suspension, is that when it is set up for handling use, the spring should have almost NO arch, a nearly flat spring isn't going to flex nearly as much as a arched spring. Guys tend to want to over-think things.... Keep in mind, back during the 60s to late 70s the nascar race cars were production based, and petty, goldsmith, issac, baker, along with a host of others, drove torsion bar/leaf spring cars at nearly 200 MPH at 3800 plus pounds, on ancient design tires....
 
Anyway you slice it a panhard bar describes a radius of a circle, thus forcing the leafs to slightly shift from side to side, "something they do not want to do."
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No argument there, but at 0.040" total forced lateral displacement in the first 2.5" of up travel the bushings both won't notice it and left to their own devices will allow 2X-3X that. So we're not talking about bending the springs sideways. We're talking about a consistent lateral location of the rear axle that the springs by themselves can not do.

A "perfectly" designed Watts bar would not do this, but I'm not even sure this is exactly possible.
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For a set amount of suspension travel it is possible. What complicates things is trying to fit the perfect design under the car.

It would be interesting to see what "the Petty boys" actually did back in those days. Seems to me there's some photos of his 70 upside down............
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Agreed, it would be, but keep in mind that what ever they did had to attempt to meet the rules. So they quite probably didn't do everything that they wanted to do.
And just because they didn't do it doesn't mean that we can't or shouldn't. If you have rules to comply with, then you're limited by those. If not then something as simple and common as a panhard bar isn't rocket surgery and should be considered as one possible location solution.

FWIW only drag racing 4 links need lateral location because the links are all parallel. With single or double converging links no lateral locator is needed. Take a look at the GM mid and full-sizes from the mid 60's up. They're of the double converging design type. I can tell you from a misguided friend's experience that putting a panhard bar on them locks out the suspension.
 
Is it a ladder bar four link or leaf spring car?

I use a Chris Alston pan hard bar in my dart but it is a ladder bar car and not leaf spring it all depends on wat u r doing with the car

Posted via Topify using iPhone/iPad
 
Chrysler engineers thought the 67 imperials needed one.
 
"autoxcuda" posted a video of his car on the track that showed how much the rear end moved side to side. I was surprised at how much movement there really was. I don't know if he ever ended up doing anything about it or not.
 
burdar said:
"autoxcuda" posted a video of his car on the track that showed how much the rear end moved side to side. I was surprised at how much movement there really was. I don't know if he ever ended up doing anything about it or not.
Click to expand...

By any chance would you know where I might get a link to that video?
 
ntsqd, That would handle axle wrap, but in that configuration, I'm not seeing how it'd mitigate side to side movement. The front of the mount would allow some mount of movement in any direction.
It'd almost have to have a bearing / sleeve arrangement at one end for vertical movement then some sort of cantilever ( like f1 suspension ) or slotted ( kinda like a leaf spring slider ) setup at the other to allow the length of the mounting points to change ( to account for movement arc )
Sorry if I'm not helping, I love the discussion, I'm a "gotta know why" person :D

Anyway, Back to the OP questions.
Who has one installed?
What handling aspects changed and to what extent?
Let's see 'em! ;)
 
His point is that they don't. They are not a panhard bar nor a Watts and got us off the track here, so to speak
 
Dana said:
Chrysler engineers thought the 67 imperials needed one.
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That's interesting. I see, though, that they also used those stupid rubber cushioned leaf mounts
 

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This pic is what I was talking to:
XA_RPO99_tramp_rods.jpg

With the wheel travel of a street car the delta in the spring's length is pretty tiny. The Wrap-Trap that I posted above uses a Ford truck radius arm bushing for the front 'pivot' and that coupled with the ideal placement of that pivot has enough give to handle the small delta from the much larger travel of the Early Bronco's springs.

player1up said:
ntsqd, That would handle axle wrap, but in that configuration, I'm not seeing how it'd mitigate side to side movement. The front of the mount would allow some mount of movement in any direction.
It'd almost have to have a bearing / sleeve arrangement at one end for vertical movement then some sort of cantilever ( like f1 suspension ) or slotted ( kinda like a leaf spring slider ) setup at the other to allow the length of the mounting points to change ( to account for movement arc )
Sorry if I'm not helping, I love the discussion, I'm a "gotta know why" person :D

Anyway, Back to the OP questions.
Who has one installed?
What handling aspects changed and to what extent?
Let's see 'em! ;)
Click to expand...
 
67Dart273, I see, 2 separate problems: axle wrap vs lateral axle displacement.

ntsqd,
ah, ok, I was looking at the red/orange pic. This one looks more solid for sure or at least only allows movement in one plane aside from bushing deflection. I was going to say that I'm pretty sure I've seen something like this on fairly new explorers out in the local yard. I understand that this doesn't have the same effect ( or is it affect ) as a panhard bar or watts linkage but I imagine that it would provide some assistance or at least increase the force needed to deflect the axle.
Awesome discussion.

69Mope, What handling benefits did you see?
 
I understand why you would see this on a coil over type rear suspension, and yes there is an amount of side movement within the leaf spring suspension. So the point is, after upgrading the springs from stock, how much would a panhard bar really help the hard cornering, or yaw of the car?
 
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