I'll would need to see statistical data for me to oppose the simple geometrical math used to justify this mod. If you look at the simple connection points of the PHB, it’s a basic connection that stabilizes the axle during suspension transitions. At no point has ANY aftermarket vendor suggested a higher spring rate due to the increased rigidity of the bushing material or adjustment of the bar to center the axle once lowered. To specify the need for a higher spring rate due to leveling of the PHB would be comparable to saying that you would negate the effects of the control arm relocation brackets with stock spring rates. If anything, relocating the PHB to a more horizontal location would justify the use of softer springs as the offset of axle movement has been reduced. Stiffer spring rates would justify the relocation more so.
It’s not the rigidity of the dampers or springs but the isolation of the axle during movement.
Try running 17x10” rims with 315/35/17 on a set of Eibach Pros with an APHR centered perfectly, then have someone in your back seat while hitting a pothole. When you see the tire shredding you will really understand the geometrical movement of the chassis in relation to the axle.

 

^^^ so true

My drivers side rear tire is shredded and my right tire is untouched. The rear IS centered at ride height. Theres more movement than you might think. Especially when going in and out of driveways and such at an angle.

Watts link does more than just eliminate side to side movement. Theres other benefits. Read the whole thread before you start bashing the idea...

 

Lowering the panhard bar DOES indeed move the roll center around (more specifically down), and anytime the roll center is moved, the effective spring rate is changed.

^^^^Learn how the suspension works before bashing other people's posts.^^^^

http://www.frrax.com/rrforum/index.p...dpost&p=125705

Specifically:


Panhard bar lowering brackets
The rear roll center height on 3rd and 4th gen F-bodies is high resulting in an inclined roll axis. When you lower a late model f-body the roll center height in the rear doesn’t drop as much as the front, therefore the roll axis becomes even more inclined. One reason that GM did this perhaps is to allow for softer rear springs so the ride quality would be improved. Since the rear roll center height is determined by where the phb crosses the axle centerline we can very easily change the rear roll center height by lowering the phb. This is accomplished by adding on phb brackets. This is nothing new, although Unbalanced Engineering released their prefabbed kit a few years back which has thrust this controversial issue into the spot light.

As covered under “basic vehicle dynamics”, the roll center height is a basic fundamental of the car’s suspension. A change in the roll center height will change the distance between it and the cg where centripetal force acts upon. Lowering the rear roll center height therefore increases the rear roll couple by increasing the lever arm length. This will increase rear body roll and if made alone the car will push. To counteract this stiffer rear springs and sway bars must be added. Then the shocks must be revalved. The basic goal in revalving them is to lessen compression damping to keep the car compliant over bumps (despite stiffer springs) and to increase rebound damping to control the stiffer springs. Popular shocks for this are Koni DA’s, Bilstein HD’s and other custom valved race shocks such as aluminum bodied Bilsteins or Penskes. Some users have made their brackets adjustable for different roll centers and leveling the panhard bar.

 

I absolutely would NOT run any watts link that is clamped to the axle. If it's not welded or bolted into a proper bolt hole, I'm not using it. There is too much chance of the axle slipping in such a design while under load. I'm not saying it's absolutely going to fail, but if it does, there is a good chance your tire will lock up against the inner fender and you are going to wind up spinning the car (and possibly getting hit). I'll stick with a PHB before I ever consider a design like that.

 

The PHB can flex when it's in compression. Also, body roll will raise and lower the chassis mount. This can cause "jacking" issues due to the angular misalignment of the PHB in the chassis.

In a right turn, the chassis mount will move higher with body roll, and, the PHB is in compression. This will cause the PHB to want to "lift" the body (if it's the path of least resistance). This can raise the rear roll center in right hand corners (to a degree) and raise the rear ride height in a corner. I'm not suggesting it's a "ton" of motion, and the sky is not falling. But, that's what a watts link avoids.

On the other hand, a good, stiff PHB works quite well for most cars nearly all of the time. There are some of us who could use it, and many people who can save their money for something else.

 

I know you were not refering to me as my conversation was in regards to a viable option to the Watts link and not the link itself.

You haven't seen me bash a post, I simple asked for data opposing the PHB relocation bracket. I did read the info you provided and it is interesting. I would like to know more about the R&D for both sides of the argument.
Regardless of your reaction, thanks for the info.

 

Subscribing...

Sam, any updates on this?

 

I wouldn't run it either without being welded, though its a better idea than locating the pivot point on the rear gear housing like saleen did. I just posted that pic so that there was an image for people who were'nt familiar with the concept.

No I was agreeing with you. I notice alot of side movement even though the rear was centered after lowering.

 

Griggs (not maximum motorsports as I first posted) also does a modified aluminum rear end cover with their watts link setup mounted to it. I questioned it at first, but I know of "dozens" of actual track cars (driven in competition) that use this setup and I've not seen one fail yet. It does actually work pretty well (though it's like the steel bracket on the back of the cover that someone else showed in this thread, not the Saleen one).

 

I'm trying, but it's hard to keep up with what we have to do currently.... and I'm not a fabricator. This is on the radar, I swear... finding time is the issue.

 

A few things. PHB's are not perfect.. but they are dead simple and light and cheap.

For those reading with slammed cars, the more you lower the car the more arc you introduce into the range of motion and the more side to side movement you get. Yet another reason we don't put the cars on the ground. FWIW, my car has the PHB slightly off the to the left to account for the arc in the movement. It took a little messing, but now, dynamically I have not contact issues on either side.

 

Makes sense. My car doesn't do a whole lot of rolling, but I can see the theory, and how it would be worse on a car that rolled a bit more.

 

Sam (or anyone for that matter),
Help me to understand what you are saying. I get a visual that is just the opposite from what you are saying (not to differ but I need clarification).
Let me try to explain how I see it…
Hypothetically, let’s say with stock springs the chassis will have full range motion of 5 inches up and 5 inches down with respect to the axle. With the stock PHB attached, you have a given amount of lateral motion based on the vector angle of the PHB and its length. Now, let’s lower the car reducing the overall full range motion to say, 3 inches up and 3 inches down (reduced by the amount of 4 inches total) and you center the car with an APHB by reducing it’s length say 1 inch to center it properly (I had to). Now the chassis sits lower and the PHB angle to the axle has been reduced effectively making the PHB sit more horizontal/parallel with respect to the axle. With the combination of overall reduced PHB length, reduced chassis to axle clearance and stiffer spring rates, how can the arc possibly be increased? How can the range of lateral motion increase? The vector angle between the axle and chassis would be greatly reduced during full range motion.
Adding in the PHB lowering bracket would only fortify my theory by making the PHB more parallel to the axle.
This is how I see it. Can you please explain how to look at it differently?

Thanks

 

Maybe I can clarify what Drgnfly is concerned about...

Stock height = PHB angle is 0 = full horizontal length = axle sits evenly

lowered car = PHB connection at axle becomes higher than chassis = shorter horizontal length than stock ride height = axle sits to the right

If PHB relocation kit is added to the axle side (is that where it gets attached?) then you can go back to a 0 degree angle. So I don't think he was disagreeing with you, but just that the PHB length change is minimal and the adjustable PHB is probably sufficient enough for most people to correct the problem as well as being a cheap solution.

 

I hear ya. I believe you mean when lowered with the stock PHB, the chassis migrates to the right (pssenger side) on the axle, therefore pushing the axle to the left (drivers side). I guess it depends on if you are looking at the car from the front or rear . The PHB relocation bracket that I was refering to lowers the point of connection at the upper right chassis mount. This mod will bring the PHB lower towards the axle making the PHB more parallel to the axle. That's why I'm trying to say that the more parallel to the axle the PHB is, the less up and down travel it will make when the car is lowered with higher spring rates.
Thanks for your feedback.

 

I'm looking at the car from the rear. Which way are you looking at the car

 

The rear too...

 

Update: We have something in the works. I'll keep you posted.

 

Sam we need some pic's!

 

We're not quite there. Working on putting together something, but need some details ironed out first. Patience young Grasshopper... the end is drawing near (I think).