The Stovebolt Site Forums The Shop Area Engine Shop Panhard verses diagonal track bar

To set the stage:
54 Chevy panel truck
Complete IFS installed
Ford 9 inch ready to install
TCI 4-link suspension kit w/ coil over shocks received. See here:
http://www.classicperform.com/Store...ks/4754RSKP.htm
Power plant will be a V8 (roughly 450HP to give an idea of the torque being applied)

The 4-link kit was to have come with a pan hard bar. In it's place, I received a diagonal track bar.

I know the difference in how they are installed but, I don't truly know what one over the other will mean to my ride. I'm not looking to take the panel to the strip (often) but...I will play occasionally. Meaning...I WILL put power to the rear every so often.

I've read several posts by a few folks that definitely know their suspensions and cause and effect. Looking for some educated answers.

Thanks in advance!
Jon

Link doesn't work.

maybe this is a start:
http://www.classicperform.com/

You are calling a panhard bar like they show in their photo, one that goes from the frame to the center of the axle. A diagonal track bar that you said you received, goes from the frame to the axle on the opposite side. Here is a web page that explains how a panhard bar reacts to left and right cornering forces and the effects of engine torque and body roll. They are talking about the longer bar and calling it a panhard. Both bars will center the axle, but the shorter bar will follow a smaller arc and allow the axle to move left and right a little more if you have a lot of suspension travel.
panhard
I doubt it would make any difference on a street vehicle as far as handling. If it hangs down below the axle as opposed to the one they show, it would make a difference in what you see from the rear.

Thanks for the replies.
I thought I'd post what I found out...

"The diagonal link is designed for racing applications only and works extremely well under those conditions"

"The diagonal link holds the rear end in the center of the car, allows up and down movement but no side to side movement."

"A diagonal link used on the street will fail, it's only a matter of time. The stress caused by the cornering of a street car puts too much bind and tension on the ends of the link and either the clevis or the rod end will fail, you just don't know when"

"For a street use vehicle a Panhard bar is tough to beat."

You aren't buying that are you?
By racing, I assume he is talking about good-old-boy, turn left at 180mph in a 3300LB race car. Underneath that car you will see two long trailing arms and coil springs. look under any pre-73 Chevy truck with coil springs and you will see what looks like the same two long trailing arms. On the truck you will see a axle locating rod/link/arm/bar attached to the frame on one side and to the axle on the other side of the truck. On the race car you will also see a rod/link/arm/bar, but this one is fully adjustable. The frame end can be moved up and down, the axle end can be moved up and down and the length of the rod(or what ever) can be adjusted. The rod ends probably have heim joints. The truck has rubber bushings and isn't adjustable. I can't remember having heard of anyone here having their truck axle locating arm fall off at 200mph or even at 200,000 miles.

You are trying to make a distinction between two different names that refer to the same thing.
Here is part of the first paragraph from the wikipedia web dictionary.

Quote
"Originally invented by the Panhard automobile company of France in the early twentieth century, this device has been widely used ever since."

History of the Panhard Bar


[img]http://upload.wikimedia.org/wikipedia/en/thumb/0/0b/Panhard_rod.jpg/200px-Panhard_rod.jpg[/img]
Full story of the Panhard company.
Panhard
[img]http://upload.wikimedia.org/wikipedia/en/thumb/8/81/PL_17_manual.JPG/200px-PL_17_manual.JPG[/img]

I am buying it a little.
They mount totally different though and have different characteristics.
To make sure we're talking "apples to apples"...

The panhard bar that can come with the kit mounts to the inside of the left frame rail, goes over the top of the differential, and mount directly onto the top side of the opposing side of the differential. On the front of the pumpkin itself (for this particular style).
The diagonal track bar starts at the back left connecting point of the 4 link and travels diagonally accross to the front right of the 4 link.

I definitely not a suspension engineer but, as I imagine (in my little pee brain) the movement of a vehicle turning, the force against and the allowable movement the two differents style would be very different.

You are trying to give the term diagonal track bar a whole new meaning. When a long panhard bar is used, it is attached to the frame on one side of the car and to the axle on the other side of the car. The bar should be horizontal when viewed from the rear. When you jack the car up, the bar will drop down at an angle(diagonal). On a race car they may have one end of the bar adjusted up higher and it will be at an angle(diagonal).
The longer the bar, the better. There is less movement of the axle left and right. The problem with the longer bar is that everything gets in the way.
[img]http://upload.wikimedia.org/wikipedia/en/thumb/0/0b/Panhard_rod.jpg/200px-Panhard_rod.jpg[/img]In this drawing you can see that hitting a bump, the bar would be bent by hitting the differential. If it were moved rearward toward you the viewer, it might hit the spare tire or gas tank. The mounting bracket on the axle would also have to be made stronger and heavier.
On your setup, if the bar went from the axle on the left, straight across to the frame on the right, the differential would be in the way. The first bump and the bar would be bent in a "U". Going forward is a compromise for clearance and it probably saved fabricating and installing an extra frame bracket.
Short panhard bars are used when you don't expect to have a lot of wheel travel and when trying to avoid obstacles such as shocks, sway bars, mufflers, tail pipes, gas tanks and anything else in the way.
Long bars are usually behind the axle and look crappy from the rear.
Call the guy you bought it from. He probably feels he is giving you a better product and it may very well be that he is.

Get away from the Panhard/Diagonal/Track bar terminology.
If you have your vehicle lowered and fat tires with very little fenderwell clearance, that short bar may very well cause your tires to get cut up. It will allow more side movement of the axle. If your truck is raised and you're running off road, you should have a long bar.
Normal ride height with plenty of tire clearance, you'll never know how long the bar is.

The cloud is lifting. What your saying is sinking in a bit deeper this time.
Maybe I should keep what I have...
Thanks,
Jon

I think Richard is misunderstanding what Jon is referring to as a diagonal track bar (or link), which is different than a Panhard bar. As mentioned, a diagonal trackbar, used with either a 4-link or ladder bar type suspension, attaches at a front link mount on the frame and the diagonally opposite rear link mount on the axle, to create a triangle within the 4-link or ladder bars. This page from Art Morrison's site shows both types of bars with a 4-link system. Art says the diagonal bar is for racing setups (drag racing), and the Panhard bar is for street use.

You hit the nail on the head Xram53. Talking to TCI again tonight, they said the diagonal bar (as shown in the pictured link) will perform the same as the panhard. Art Morrison is stating that there is indeed a difference and that the panhard is best for street usage.
Who the heck do I believe?

Given what Art Morrison says about the diagonal links failing in street use, whether it's really true or not, I don't think you could go wrong with using the Panhard bar, just to be safe.

I saw reference somewhere about the diagonal links bending under cornering loads, if they're not beefy enough. They have to handle quite a bit more force than a Panhard due to the angle of installation. They may also somewhat hinder axle articulation, though that may be a disadvantage of 4-links in general.

I agree. I sent and email last night to the head sales guy. I shared all of the different things I had learned and expressed that I might always have some doubt if I didn't switch from the diagonal to the panhard.
Haven't heard back. Probably have to give them a call tomorrow.