Ok, I'm a little bit confused about the panhard rod. From what I understand and from what i've seen, it connects to the axle on the driver side of the car, and connects to the body of the car on the passenger side. Here is a little picture I drew. The car's gray, axle is brown, rod is red, and the blue is just a centerline.



Now, this is all nice if the car stays at stock height. But I am wondering about lowering springs. The way the rod is setup, with a couple pivot points, makes me think that if the car is lowered a couple inches with springs, the whole rear axle is going to be out-of-center with the rest of the car.. See my second illustration to see what I mean:



See what I mean? Lowering the car is going to bring the axle closer to the body, and by doing that will make the panhard rod force the whole rear axle to move towards the driver side of the car.. Am I correct in this? Will lowering the car make getting an adjustable panhard rod mandatory?

Here's a 3rd image I just made with the two images on to of eachother, plus a green line showing how the panhard rod would pivot..

 

Very good point. I also, do not know the answer but am very interested.

However, something doesn't add up to me -- from your illustration, you would get the same action under normal compression with the stock suspension. And, I can't imagine the whole axle would move laterally under normal loads.

Here is an interesting article on a different issue with panhard bars, but there are some better illustrations:
http://www.steeda.com/PR/Mustang/panhard/panhard.htm

BTW, here is a good shot of the rear suspension:
http://bradbarnett.net/mustangs/timeline/05/05/64.jpg

Ultimately, I wouldn't worry too much about it. If companies like Saleen and Steeda are keeping stock panhard bars with the springs, than it should be alright.

Now, if you are a hard-core racer, that might be a different issue.

 

ovn3,
That is an excellent drawing and yes, you are correct but there is a couple of items you should be aware of. First, the Rod is much longer than you protray relative to the size of the car/axle. That means the left/right movement is much less for a given up/down movement than it appears in your drawing. Second, the angle of the Rod starts out much closer to neutral than you show so again the left/right movement for very small angles is less than for larger angles.

That being said, you are correct in your analysis of the results of lowering the car. That is why the aftermarket has already come out with adjustable Rods.

The Boss Hog
(Who knew that Trig whould actually come in handy . . . . . . . . )

 

This was my exact question when I asked about lowering springs.....I read on some site (can't remember which one) that if you add lowering springs, that the rear end shifts to the left slightly and that they recommend purchasing an adjustable Panhard rod to correct this.

Also, if you browse through the Steeda site and look at their other suspension products, you will see that they suggest certain items to purchase when buying the lowering springs (but they don't mention buying other suspension parts under the lowering springs description...???) Some of these items include: Control arm relocation kit ($49.95) X-5 ball joints ($99.95 ea)

Here is the description from the Steeda site for the above items:

555-8108 X5 Ball Joint $99.95


Any time you alter the height of your ride, as you do when you install lowering springs (like our Steeda Sport Springs), you upset the steering geometry. You can easily bring your front end back into spec with a set of our X5 ball joints. Restore roll center geometry and lower you car's center of gravity.
NOTE: Require 18" or larger wheels to clear at full rebound.



555-8116 Control Arm Relocation Kit $49.95

Lower your chariot's center of gravity and maintain the correct roll center (a good idea when using lowering springs) with the Steeda Control Arm Relocation Kit. Raises the control arm location by 3/4 of an inch (19.05 mm).
NOTE: Welding required for installation.


On yet another site, they mention replacing the shocks also.....

So exactly what do you need to purchase when installing the lowering springs??

I asked "2005RedGT" this question, as he had the Steeda lowering springs installed on his car and he said he experienced no problems.

But as "ov3n" has illustrated, I would believe that you should at least have to buy an adjustable Panhard rod.

:scratch:


Mike

 

Wouldn't the 3 rear trailing links keep the axle moving in a vertical plane? The panhdard bar is not the only thing dictating the angle of movement -- it looks like it would get increased pressure, but would that be enough to twist the control arms? And, with the small angles we are talking about here, would that be an issue?

Orthoguy -
Everything I have learned about lowering springs says the only thing you NEED to install lowering springs is a new alignment. However, the lower stance and higher spring rates increases the strain on the dampers, which can cause a bumpy ride and a blowout. So, they are recommended, but not required. Also, since the geometry of the suspension has changed, all that Steeda stuff (ball joint, arm relocation kit, bumpsteer) works to ket the front suspension as close to stock geometry as possible. Not really noticeable on street driving, but better none-the-less.

 

Rampant,

Nope. The whole POINT of using a panhard rod on the new 05 was that they could decouple the side to side location job (panhard rob) with the for/aft location job (three links). Because the links no longer have to control the axle laterally, they can be designed to do a much better job of controlling the axle without hitting issues of binding and other problems. Basically, the links are not built to locate the axle side to side and they can't do it. Not well, anyway.

There is another lateral location design that works better than a panhard. I can't remember it's proper name at the moment, but basically, it has a link attached to the back of the diff housing facing up and down. You have a short rod that goes from the top of the link to one side of the chassis and another short rod that goes from the bottom of that link to the other side of the chassis.

As the diff moves up and down, the link will rotate slightly. Because you still have the same relative angle for each side to side rod, the diff stays right in the middle but it can move freely up and down. Better part, but a LOT more complex and expensive (and heavier) than a panhard rod. Not worth it for a production street car.

 

I think the other setup you are thinking of is called a torque link. It can be done with shocks or rubber bushings. I raced a modified with that setup. Worked well.

There is also a "J" style panhard bar which is very short & works well in tight confines.

I raced an older Trans-Am mustang in GT-1 that had a 3 link & panhard setup. Here is what I recall.

A panhard bar is a lateral locating device. It coneects the rear end housing to only one side of the chassis. The center height of the bar will determine the rear roll center. By changing the height of the bar you can change the handling. Raising the bar will make the car looser, lowering the bar will make the car tighter. The panhard bar also helps reduce bump steer & body roll.

If you lower or raise the car with springs you are going to change your roll center, therefore changing the effect of the panhard bar.

 

RRRoamer,
Thanks for the clarrification. I am (obviously) really new to panhard bars and am very curious to learn more about them.

I am still a little unclear though as to what happens under compression.
When the rear sqauts (on acceleration), does the rear portion of the body then shift to the right? Would torque accentuate this action, or help keep it in check?

I would imagine lowering springs would be like the suspension was in a constant state of slight compression (without the built up energy). Is this a correct assumption? If so, the same problems that would happen with lowering springs would happen under suspension compression. Right?

 

But, would that affect lateral positioning of the axle in relation to the body (i.e. would the body be shifted right of centerline in comparrison to the axle)?

 

My GT-1 car was tube frame. So every time you made a change you were constantly scaling & aligning the car. I don't ever recall seeing the rear off center. When I did alignments you always used the center line of the car as your constant.

 

Don't get TOO wrapped up in this. Making a few assumptions here for the geometry: 48" long panhard bar. 5" total suspension travel (2.5" up and 2.5" down). So based on simple geometry, you would have less than 1/16" difference in lateral location.

The rubber in your tires could EASILY handle that much deflection. And if you are rolling, your suspension won't really notice it. All in all, it doesn't really matter WHICH parts move relative to the other parts. They move a bit. But not enough to really worry about.

 

RRRoamer, the name of the part you mentioned before is the Watts linkage, used in conjuction with a torque arm sometimes(especially by Griggs,i.e.Eleanor)just so you know. B)

 

THANK YOU! That was bugging me...

 

Just as an aside, there's a company which now makes bolt-on Watt's Link setups for Fox bodies.......proving once again that with a little attention, even they can be competitive and handle properly.

Evolution MS Watts Link

 

FINALY--A reasonable voice. THANKS.

 

Your welcome. After getting involved in this thread, I stared to wonder how much it moved myself, so I did the math. I was in a generous mode, so I shared it with everyone else too!