F1Fan

Hi Norm!

Exactly! With the GT500 LCA's the importantpart is in the design of thebushing durometer and the high misalignment capability of this type of joint with reasonable bushing durometers. You will also note that the bushing design is directional. That is to say the bushing is designedto locate the axle morepositively along the LCA's long axis which is the only direction that loads are designed to be introduced to this suspension component. The bushings are more free to move vertically and around the perpendicular axis of the bushing joint due to voids in the bushing material and these voids also serve to reduce NVH at the same time.

As you know the real limitations of a solid or conventional constrained poly bushing are largely due to limited freedom of movement. When these limits are passed or stretched they can cause artifically induced and unanticipated increases inrolland/or spring rate. These same poly bushings also tend to fail if they are elongated much past a few percent which is why you have to inspect and replace the things so often.

A voided polybushing isexactly where I was goingwith this and I have posted lengthy descriptions on this idea here and in other forums. There are some interesting possibilites in the market for this type of joint and I'm pretty sure they could havethe samelifetimeof ahigh-end 3-piece/lined rod end with much better NVH and practically the same level of location compliance.

Have you seen or are youfamilar with the Currie Johnny Joints? They are fabulousjoints witha long streetlife,verylow NVH and very good compliance. They are also reasonably strong and easy to buy from a pretty good company. Off roaders have been using these things for years. Thatis actually where I first encounteredthem and I was amazed at the abuse they took over and over for years on everything from these tiny lightweight articulated suspension4x4 rigswith these blown V8 monster motors toIMOTFB 4x4's with veryhigh mass and even bigger motors than the articulated 4x4 contraptions. They seem towork pretty well under grueling conditions and can tolerateamazing levels of misalignment. I like'em! Look at this LINK!


Cheers/Chip

F1Fan

Hi Dex,

Don't bother, we all know what GT500 LCA's look like and as you say they appear similar. But that is not the real story. Read Norm's post.

HTH!

RodeoFlyer

MM's with rod ends at both ends FTMFW! [sm=gears.gif]



I have the UMI/Strano swaybar endlinks. Well made.


Seriously - we have lovely sounding V8's and at the very least 500W stereos. The whole NVH thing is blown WAAAY out of proportion. With a live axle hopping around on bumps anyway you're not gonna feel any more from the rod ends.

Quiet, supple rides are for minivans!!

Norm Peterson

Yes, I've been aware of Johnny joints for a while, and I suspect it's what the "polyball" was modeled after. Mark Savitske at scandc.com carries the Johnny joints and is locatedreasonably locally to me. Given that his "skunkworks" has put together at least one upper class (possibly unlimited) Silver State Challenge car and developed a bolt-on C5-based front suspension upgrade for GM G-body cars, that he's carried them for a number of years at this point makes for a pretty strong and thoughtful recommendation.

I've spent some time trying to understand the whole business of compliant bushings, and it ultimately comes down to the fact that of the six degrees of freedom at each pivot, you really only want high stiffness in at most the threeforce directions or else the control arm is going to induce some amounts of roll and ride stiffnesses (and beat up on the control arms a bit if you're just plugging them into your OE open-section arms). For cornering, anyway. In drag racing, there might be some advantage in having induced effects - anything that opposes squat either by stiffening against it or damps the squatting motion is likely to be beneficial. Since the straightline business is arguably the bigger side of the performance market, that's my guess as to why that's about all that's been out there.

Anyway, there's a significantly modified set of ordinary poly in the LCAs in the thumbnail car. OK last I checked, though it was starting to wheel hop again at the starting line at auto-X so I think there's still a durability penalty involved. You could clearly feel the before/after difference in lateral head-toss going over shallow drainageways at an angle. I imagine that you've come across the results of the MM bushing bind study done some years back. I'm semi-educatedly guessing that an 80% reduction in their poly/poly numbers is easily achievable by careful voiding, putting you barely stiffer than OE in roll.

Voided poly might not get quite as good or be quite as durable as a rod/poly arrangement, but might be an acceptable low-buck alternative for those less fussy about bind-free kinematics or are more severely budget-limited.

I still have to crawl underneath my car, but that won't be happening this weekend.
[IMG]local://upfiles/62186/791801AD50C74571BCF31337B0B0632E.jpg[/IMG]

This maybe shows it better
[IMG]local://upfiles/62186/D4FB0A8D37814696975D8EC5D46B168E.jpg[/IMG]


Norm

2007GT/CS

+1

Norm Peterson

Thought it was you that Sam was referring to.


NVH? . . . nah, just the N when you're driving around on the street. Suspension 'clanks' are even worse than me when it comes to keeping a beat.


Norm

F1Fan

Hi RF!

Well personally I likenice quiet cars withmoderateride motionswithgood body control, sensitive steeringand reliable, predicable limit handling with a reasonable power to weight ratio. It must be all those years of driving911's or something. NVH? What good does that do anyone?

But having said thatI do love the almost brutal feel and feedbackthat my S197GThas compared to the smooth machine like German sports and GT street cars I've grown up driving.It sort of makes me think you could be right. 8^)

HTH!

docwine

I have the very LCA's he is showing above from UMI (from Strano) and love them. They are strong and don't bind or convey too much NVH.

F1Fan

Hi docwine,

I've got a pair of Steeda RaceDouble Adjustable LCA's in my car withSteeda poly bushings on the chassis side of the LCA and3-piece Teflon lined rod-ends installed on the axleside of the LCA. I've also got a pair of Aurora's mil. spec 4340Teflon lined rod-endsfor whenthe Steeda supplied rod-endsstart to wear.These LCA'scost a bit more than the single adjustable UMI shown but these are double adjustable like the UMI LCA'sSam sells for $220. Oh wait a minute,that's the same price asthe Steeda50/50 double adjustable LCA's cost! Of course the Steeda double adjustable LCA's usechrome-moly tubing and are cad plated so you can see right down to the welds instead of the heavily powder coated mild steel DOM UMI uses.But I agreethat QA1 ends are some of the better rod-ends available buttheyall wear out sooner or later.

HTH!

sd07gt

check out edelbrock's LCA @ UCA .... they are using Johny joints.. or a copy of them ! ....