Yes.. ive searched the forums, but am still unsure on a few things... So i was reading comments and dont feel there was a definitive answer... Im looking at rear lower control arms and the panhard bar (withRELOCATION KIT)... Obviously adjustable is the way to go, but Im still unsure of what application requires a certain setup... The panhard bar and LCA's both have 3 options... Poly/Poly, Poly/Rod, and Rod/Rod combos to choose from.... So with that said, depending on application, what certain setups benefit from each combo? Whats the pros/cons?

 

poly/rod end is the way to go with just about every setup. rod/rod, is better for a race app, because of some extra noise and maintinence. poly/poly, is not a goo idea because they bind too much.

defiantly an on car adjustable pan hard, just makes life easier. I opted for a rod/rod pan hard because it does have to move front to back a little. Didnt pickup much is any noise

 

Appreciate the answer... Was curious if you could elaborate just a slight bit more... I get that on a dedicated DD a poly/poly combo would suffice.. Say on a street/strip car that has Rod/Rod, would the noise while driving on the road be real bad??? Or better yet, are there any setbacks/issues? Say for example, one was to use a Rod/Rod combo on their DD, is the extra noise the only problem (other than maintenace as you had stated) or would running that cause other unwanted issues or wear and tear?

Also, just wanted to clarify, you suggest poly/rod end is the way to go... For both the LCA's and the panhard?

Other issue is this and i know its individual specific... But who would be the best to go with when i comes to these 2 parts??? I assume as well that since id like 315's on the rear id need offset bushings.... So these are my questions...

1) say i wanted Poly/rod, there'd probably be clearance issues for the 315's so id need the rod bushing to be offset, right?.... (havent seen a poly/rod offset bushing combo...or just may have missed it)

2) What the difference between a roto joint vs a rod??

 

depending on the wheel and location in the wheel well, you may not need offset bushings. If you do need offset bushings, you need a rod/rod arm, never seen an offset poly rod arm, except my custom ones

the rod ends get noise when they wear, when they are new, they are pretty quite, you may pick up some road noise, like vibrations ect from the rod ends, which is another reason poly/rod combo arms are popular.

i owuld not use a poly poly arm on a DD or any location that requires some side to side flex and twisting.

Like i said before, i like the idea of the rod/rod panhard bar because the bar has to move forward and backwards a little, with a poly end, it will bind a little.

rotojoints cant be offset. They have a larger range of motion than a rod, unless the rod end has high misalignment spacers. The roto has a delrin lining, so no metal on metal wear. And they are rebuild-able, and have adjustment to remove any slop that occurs from wear, a special tool is usually required. they are kinda nice

 

Sounds good...Thank you sir... I guess once get and put on brakes ill have to check the wheel and location...

 

keep in mind that the panhard bar relocation kit is not really recommended unless you NEED it for exhaust clearance.

 

Why do you say that?? Im not sure if ill need the clearance, who else makes a good upper panhard bar?

 

it changes the rear geometry. And, not in a good way. It moves the chassis side of the panhard bar down without moving the axle side. You will need to make other adjustments to compensate and that can get tricky. The stock upper is fine. Its mearly a brace between the two frame rails that doesn't see much load.

 

Okay, so it puts the panhard rod lower on the passenger side... Isnt that the same thing that happens when you use drop springs? So am i correct in stating that if ssomeone was to use the relocation kit they'd have to make a bracket for the rear end to lower the bar on the drivers side?

 

yes, that is correct. then, by lowering the bar on both sides, you should use stiffer rear springs.

 

So then i guess the statement on BMR's site about lowering the panhard rod while maintaining the correct geometry is presumably false.... I wouldnt think they'd make the part unless they thought it wouldnt be an issue.. (Geometry wise)... I figured if the passenger side is lower and puts the panhard bar on more of an angle, it pulls the axle towards the passenger side, which then an adjustable panhard would come in handy to center the rear...But then again, im still learning...Would that kit affect geometry that drastically??

Id do that because now the bar still contains the correct geometry but sits lower, so id need stiffer springs??? Dont really know what your getting at. I dont know too much about suspension geometry yet.

 

You want your panhard to be level at ride height not cocked so when your car leans/sways it moves equally in both directions not just closer to the pass. or driver side.
http://www.jegs.com/i/Jegster/550/41...oductId=754011

 

How does the upper PHB not see much load? Without it, the panhard bar would likely get ripped out of the car when you start taking turns at any decent speed. When you look under the rear of your car, on the passenger side you will see a large U-shaped piece of metal extending downward, and at the bottom, one end of the PHB will bolt up. Roughly 1.5" above that you should see the PHB brace bolted up.

(Here the suspension is unloaded so the PHB is at an extreme angle but you can see the large U-shaped bracket and all the mounting points. Picture courtesy of UMI Performance.)


That PHB brace essential makes the long U-shaped bracket shorter by having mounting point closer to the PHB mount. Then becuase the PHB brace is counteracting the forces of the PHB to keep the U-shaped piece of metal in place, it is seeing only slightly lower forces then the PHB itself.


Yes, when you lower the car from the stock ride height, you will be lowering the passenger side PHB mount however much the rear of the car was lowered. Lets say the rear of the car was lowered 1" and you just installed the PHB brace which lowered the passenger side PHB mount another 1.5". You have just lowered the passenger side PHB mount 2.5" and most likely sent it a good bit below the drivers side necessitating a lowering mount to be used on the rear end PHB mount to level the PHB.

(Here is a picture of BMR's PHB brace from their website and you can kind of see that the passenger side (left side of picture) is lower then the drivers side. Picture courtesy of BMR Fabrication)


Ideally you want the PHB to be level with the ground when the car is resting with the suspension loaded. If you have access to a welder and drill press or even hand held drill, making the rear end mount will be an easy task. If you feel lazy you can purchase the mount from Jegs and then weld it in. (Just as a heads up, the Jegs piece has gotten several bad reviews due to the lack of quality, but here is a link to it.)


Correct, the BMR piece does not retain correct rear end geometry. You are also correct when you say "I wouldnt think they'd make the part unless they thought it wouldnt be an issue geometry wise" because it really isn't an issue and more then factory build tolerances were/are. The car will still be drivable and I would be willing to bet that 98% of drivers wouldn't know the difference. You are also correct when you mention using an adjustable panhard bar to recenter the rear end under the car. It would adversally effect rear suspension geometry, but it is nothing to worry about unless you get competitive in autocross or road racing.

When you use a kit similar to the one BMR offers which lowers the mounting height of the passenger side PHB and PHB brace, and you also use a bracket on the rear end to level the PHB you are actually lowering the rear roll center height. Doing this puts more leverage on the springs and swaybar during any bodyroll. Many people move up to a stiffer rear spring rate to counter this change, but it the bar is not lowered much, you can get away with installing a larger rear swaybar as a much cheaper alternative.



I hope all that made sense.

 

Makes about 85% sense... Basically everything except you last paragraph... Im still a lit iffy when it comes to roll centers, instant centers, body roll... I have a general idea of what your referring to, just having a hard time applying it to what were talking about... Know of any good vid's that show different changes in the suspensions geometry and angles... Im a visual learner.

So just lowering the panhard bar lowers the rear roll center height???? Why? You think you could use some pics as reference and show me how this works? I think that i need to understand where the rear roll center height is first, then i might understand how a kit like that lowers it. I think once i have a grasp on how that works ill understand why theres more leverage on the springs and swaybar during bodyroll, there in understanding why a stiffer spring rate will counter it.

 

The brace doesn't see as much load as the panhard bar itself. Maybe I shouldn't have said it doesn't see much load. It mounts between both frame rails. It does see some load from the PHB but not like the PHB sees being connected to the axle. Many people do not see the need to replace the brace even in racing applications.
98% of drivers may not notice it...in most situations, anyway. I think back to an example Dean posted a short time ago about if you lose control at highway speeds and what the car would do with improper PHB geometry when seeing sudden side loads/body roll in either direction.
2.5" is huge! On a racecar, you might move one side of the bar 1/2" to get a desired change. Maybe 1".

roll center is where the body pivots over the suspension, basically. (someone please do step in if I don't nail this all down correctly) Rear roll center height is essentially the mid-point between the two mounting points of the PHB. Body roll is based on this point and your center of gravity height (which is an imaginary point calculated through use of scales and raising one end of the car and weighing again). When you lower a roll center and don't lower your center of gravity point, (in most cases) you give the center of gravity more leverage against the "pivot point" or roll center which results in more body roll and potentially loss of tire contact. When you raise the spring rates, this counteracts the body's ability to roll. The sway bars will also counteract the body's ability to roll.

 

[quote=AM91Camaro_RS;4438811]
2.5" is huge! On a racecar, you might move one side of the bar 1/2" to get a desired change. Maybe 1".

[quote]

Yep, 1" is HUGE. I ssometimes only make 1/8" changes on the racecars. Most of the time it is in 1/4" increments though, and then 1/8" to fine tune.
I think anyone buying that panhard brace that accidently lowers the chassis side mount that much can subjust the manufacturer to a lawsuit since nothing is discl;aimed aboutr the dramatic factory suspension altering in driving charateristics. That unit will make the steering effort soheavy its rediculous , as well as the lateral jacking an squating unbalance left to right corners compared.

ps- Alan, you are very close in your explination of roll centers. The onlyu thing I can add is the roll center does actually migrte laterally slightly in dynamic load off center of the PHB length due to changes in load of spring rates on the solid axle. The pivot laterally favors the higher rate (the rate goes higher with compression load- the Roll axis yaws slightly) For laymens terms though, it rpobably is best to leave ypour disription so as not to confuse people about RC migration laterally. Just a static RC point is fine for them to grasp, that would in fact be the center of the PHB length ewhere it crosses the centerline of the chassis.

Dean

My wireless keyboard sucks