need a track bar measurement

[lars]

Looking for the diameter of the stock Bronco track bar. I don't have one anymore.

I understand the 76/77 version may be different (bigger) than the earlier ones. Would like diameter of both, if anyone has the numbers.

Thanks!

 

[JIMS74]

my 74 trac bar dia. is a 1 1/8"

 

[lars]

Thanks for posting!

Hopefully now I can get someone to chime in with the late size

 

[cvbfireman]

ive got an extra one if you need

 

[DirtDonk]

Not sure if the later ones were actually larger in diameter Lars. Might have been, but the main difference was the upper mount was an oval shape, as opposed to the standard round ones before then.
Pretty sure my aftermarket (Superlift) one is also 1.125", but I can measure if you need a non-stock reference.

Paul

 

[lars]

cvbfireman, thanks for the offer, my trackbar is longer than stock by about 6" so the OEM one won't fit anymore. I have some obscure math geek stuff in mind...

Paul, I'd be interested in knowing what the aftermarket one measures. I was messing with the Euler buckling and natural frequency calculations. Both go as the square of length, so by increasing the length of the track bar from about 30" to about 36" as I have done makes a big difference in structural behavior. More likely to act like a jumprope when it gets an input from, say, a sharp-edged bump on the freeway. The frequency will still be high, but it could be enough to feel. I am getting some of that in the front end at speed. Nothing like the usual death wobble- this damps out almost immediately.

I've noticed that every full size truck I've seen that uses coil springs has locating rods (track bar, panhard rod, whatever) much larger in diameter than found on early Broncos, not to mention steering links. Arguably heavier vehicles, but not as much as you'd think, especially when you add much larger than stock tires to the mix.

I'm going to bump my track bar up to 1.25" diameter, just for grins. May not sound like much, but there's that math again: the bending stiffness of a circular rod goes as the 4th power of the diameter, so a small increase makes a huge difference in stiffness.

 

[Madgyver]

Thanks for posting!

Hopefully now I can get someone to chime in with the late size

Lars,
Here is a 77 tracbar. I measures just a hair under 1 3/8"

 

[lars]

Lars,
Here is a 77 tracbar. I measures just a hair under 1 3/8"

Thanks, Mad. That lends credence to my wacky ideas ;D

 

[DirtDonk]

Vintage Superlift EB trackbar is 1.130 or, for all intents and purposes, 1 1/8".

I presume the current crop still uses that diameter, but they did make a change to the way they were put together a few years ago. You can see it especially in how the tubing is formed at the ends and welded to they eyes.
So they may have changed diameters too, but I don't have any in front of me to double-check like I used to.

Maybe someone at Wild Horses has a couple of them out of boxes that they can measure for you too. They cater to the '78/'79 crowd as well, so likely have the full-size version in stock.

And to add to your library of factoids, Superlift at least, used to offer three different trackbars. The shortest was the EB, then the full-size Bronco, then the longest was for the F150. When I saw the different part numbers, I pulled them all out of their boxes to see what was up, since I was trying to get an off-the-shelf part that I could use to make a longer trackbar. Unfortunately for me, the longer ones were just not sized right for what I was capable of making a mount for at the time.

Oh, and have you determined what, if any, effect on your calculations the bend at the lower end of the full-size trackbars might have had? Or just what it was for in the first place?
I'd be curious to know.

Paul

 

[NicksTrix]

interesting lars, very interesting.

 

[lars]

I dunno know about bends, except that in a perfect world I'd rather avoid them. They guarantee that the thing will flex (act like a spring) more than a straight bar of the same OD/ID.

In my case the track bar is somewhere on the far side of 36" eye to eye (it's pissing rain and I don't feel like going out to confirm) with probably 30" of that being tube. Which, in my case, is arrow-straight. I'm on a mission to de-slop/de-vibrate/de-wobble my steering to the extent possible. Getting closer...

 

[lars]

Oh yeah... switching from my current 1-1/8" OD x 11/16" ID tube to a piece of 1-1/4" OD x 3/4" ID tube yields roughly a 54% increase in bending stiffness with only a modest increase in weight (about 1/2 pound, I think). With a similar impact on natural frequency (higher, a good thing). What that means in the real world, I can't tell you.

1-1/4" is about the biggest I can go due to limited clearance with hard parts at the axle end, or I'd bump it even bigger.

 

[methcat]

Oh yeah... switching from my current 1-1/8" OD x 11/16" ID tube to a piece of 1-1/4" OD x 3/4" ID tube yields roughly a 54% increase in bending stiffness with only a modest increase in weight (about 1/2 pound, I think). With a similar impact on natural frequency (higher, a good thing). What that means in the real world, I can't tell you.

1-1/4" is about the biggest I can go due to limited clearance with hard parts at the axle end, or I'd bump it even bigger.

do you remember by chance what wall you used for this combo? i'm guessing it had to be larger than .25" wall, so you still had meat for threads (or did you use .25" and weld in inserts? or maybe the heavy duty shank rod ends with 7/8 threads?). and did it raise the mode enough to notice?
thx