OK, here is a video. Excuse my babbling. A little embarrassing... I do know that in watching it again that my spewed facts are not all that accurate, but there was no rehearsal...
I in no way feel to be an authority on suspension, but I think this might clear up why I have always disliked these hard plastic bushings.

http://www.vimeo.com/5185383

 

When removing the ball joint do I need a 'special' tool and/or will a standard pickling fork work? For that matter are there any other special tools I might need? I must sound like such a noob, but I'm not inexperienced working with cars (including a complete rebuild of my '64 GTO 389 Tri-Power), just this special little car ...

 

Outer ball joint can be removed with a pickle fork, but much care needs to be given if you plan on reusing it. Not much reason not to always replace it with new though. The inner ball joint housing can be unbolted from the subframe and left conected to the arm. No reason to replace unless it's bad, but easier then the outer to do so.
Getting the outer ball joint out of the hub carrier can be quite hard.

 

Wow, Greg, EXCELLENT video! Thanks very, very much!

 

Great video, Greg. I understand things better having watched it.

 

Hmmm...mine move very easily except at the extremes. Are the studs free-floating Greg? In other words, or, do those have the motosport attachment in the back?

Seriously, with the tip of my finger I can raise mine to full compression and the arm will fall to full droop with no problem. I definately sense bind at the extremes, but if my bushings did what those do they would be off in a heart beat.

I'm at a loss to explain the difference...and the video is clear.

 

So how would a 0 offset polyurethane bushing like a Powerflex compare to the offset Bavarian Autosport bushings in terms of this binding?

 

Michael, what brand/type of bushing are you using?
Not sure what you mean by free floating studs and "motosport attachment ".

As one can see with the REAL motion of the rear of the control arm makes any 'solid' type of material that is used for the rear bushing an issue.

 

The same. Being offset has nothing to do with added binding. Best is to really watch the closeup of the motion of the arm in the bushing.

 

I didn't realize it was a different bushing...I assumed this was Powerflex with the motosport plate on the back.

The Powerflex is a two piece bushing and the stud is allowed to move in and out of the bushing as it should. Where the PFlex runs into trouble is at the extremes since as it moves in and out its axis with respect to the front ball joint pivot changes.

That particular bushing must be repsonsible for some very unsettled dynamics...80lbs in compression and 55lbs in rebound is a lot of additional work for a damper to keep after...more so, I believe, since this bushing is also repsonsible for loading up the spring. So we have introduced another ride frequency - beyond tires and springs which the damper has to control...and the frequency is portentially out of sync with all else.

Greg, the Pflex bushing isn't even close to the style in the video. No, I'm not making a video this weekend. I'm not sure the off-set axis isn't the difference between the two...if you assume the stock axis is sympathetic to half way between full compression and full droop, an odd axis may - and apparently does - create a hell of a lot of bind at any point in travel. This is also a one piece unit? If so it is not designed to work the way this control arm should work.

 

Michael, I would love to be able to test what you have. I'm not convinced that what you describe with the motion is what I am seeing. In and out is not the problem here. It's the side to side motion as the arm does not truly rotate in that bushing.
Is this what you have?

 

Yes

I absolutely agree, side to side. But because the PFlex is not binding at ride height - it is on axis - it will bind only slightly at the extremes. And the inner piece is softer than the outer and moves in and out with travel.

I can tell you that if I remove the lower ball joint and raise the LCA as far as I can, the only thing stopping it from hitting the ground is the sub-frame. It will hit the sub-frame for sure.

Please don't make me remove the ball joint...the car was aligned Even after winter when all of the salt and grim caused these to move with friction the arm still hit the sub-frame when raised.

 

This binding at the extremes with powerflex would explain the tiny creak when my suspension is at full squish.

Even if the binding causes undo effects, I'll never go back to the stock ones. I love the tightness and feedback I get with the polyurethane bushings.

 

dunno...if these are lubricated they make no noise at all.

 

Well, now you guys got me thinkin' - I watched closely the movement of Greg's (Jason's?) offset bushing and realized what he was saying - but this same level of resistance may (would) not occur w/ the 2 pc (i.e. see photo of the M/Madness bushing at top of thread) - was also wondering if a dry graphite (which I have on hand) was used to lube insert surface if that would reduce binding (and last longer) than a 'wet' lube...

Also noticed a similar movement in the OEM bushing, just 'squishier' - easier to visualize the failure point of the OEM's...

If anything I'm not installing the offsets!

 

Well, the squeak does not occur at each full squish incident. Maybe it's due to road grime or something.

 

First, what is up with this website today? Holy crap slow!!!

Grim will cause some odd noises...lubricate at least once a year.

Alta is the same as Powerflex...I beleive. Powerflex include copper anti-sieze...I use either silver or copper.

I may decide to remove a ball joint and make a movie...not to prove anything here except that the Pflex has less bind. Greg's observation of the other bushing is spot on and the amount of binding is alarming!!! Now I know why you hate these things my friend.

 

Cool! Now I've not only opened a lively discussion, I may be contributing to excessive bandwidth or somethin'! (and I was cussin' Comcast - sorry)

Just got off the phone w/ Way (Motor Works), changed my order to the PowerFlex's - ate some crow on that one, he did try to talk me into the P/F's when I ordered, but he was graciously accommodating when I called back to change order at 4:55pm - big THANK YOU there!

2 notes: (1) will document (vid) the install, so nobody has to take anything apart - not the first time I've been the guinea pig - (2) he also mentioned that the PowerFlexes did not come w/ the anti-seize (but I have that on hand). He had some additional comments that I'll let him share...

 

Now you guys are confusing ME!

Meb, Alta is the same as the Powerflex? I thought Alta only offered their PSRS bushing.
I am still not sure what this PowerFlex one is. The one I pictured above?
Still, do understand this. There is NEVER any perfect "spinning" or pivoting point with this control arm at any point of travel nor with any bushing available. Just know, the firmer the bushing, the more restricted the motion. I tested a Delrin bushing and the movement was restricted about 99.%. Yes, the control arm could only travel about .5", and that was due to play in the bushing carrier.
What you see in the video is what you get, no matter what bushing is used, with the possible exception of the Alta, as it seems to be on the right track, but I personally have not touched one.

 

Yes, that is the PowerFlex...
It is similar in design to the Mini Madness-branded bushing shown at the top of the thread...

 

Which brand are these in the picture and the ones in your video?

 

If I may: the above photo is the Power Flex Bushings http://www.waymotorworks.com/product...cat=285&page=3



The Polyurethane shown in onasled's video is from Bavarian Autosport, an offset polyurethane of their own design > http://www.bavauto.com/shop.asp (under "clearance", then "performance parts"...


[quote-"Bavarian Autosport"]







Part Number Description Price Qty. N52614BAV Performance Tuned Front Control Arm Bushing - Offset For More Caster - Sold Individually
Clearance $49.95
(orig. $79.95)[/quote]

 

Anti-dive is only a function of how the suspension geometry couples to the chassis. If you hit a bump with an anti-dive suspensions, it's not "locked" it's just balancing forces at play on that suspension member. My mustang has a lot of anti-dive dialed into the suspension, and in the back, it's via a very low contact point for the rear trailing arm where it hooks to the axle. The force that fights the dive that would be there via a less biased design isn't "lock up" but rather engineering torques on the rear axle housing via braking forces. This creates a counter acting torque on the trailing arm that fights the lift inherant in unbiased designs. But the deflection of the supension over bumps would be the same for a 1/2 change in road surface as if it didn't have anti-dive. If you were to put scales under the tires of cars with anti dive geometry and non-anti dive geometry, you find that the weight at each corner is pretty much the same. (to first order it is exactly the same. The differences between the two situation has to do with the motion of the center of mass and the contact patches as the suspension moves.)

Weight transfer is purely a function of location of the contact patches vs the center of gravity of the car and the acceleration (lateral or longitudinal) that the car is undergoing. It's a function of geometry only, and no amount of anti-dive or lack there of will change it.

As far as the offset bushings, once again we have some compramises at work. Personally, I think the stockers suck. They are so soft that they don't really control the suspension geometry and lead to less stable extreme handling. And they don't lasts for shiit. Some have self destructed in as little as 30k miles, so whatever virtues they have as a bushing is short lived for sure. So one gets a better control of the geometry and give up some spring rate linearity. What's best? I honestly don't know.

The Alta PSRS uses a delrin ball as a lower cost spherical bushing. The problem isn't that too much, but the knocking some get (me included) because of the mounting of the tube that is used to make the control arm shaft round instead of hexagonal.

Anyway, sorry to be late to the debate. And Greg, good to see someone else engineering solutions for the car.

Matt

 

You most definitely earned that 'Dr.' in your name. Good explanation Dr. Obnxs.

 

Doc,

Anti-dive works any time weight is transfered to the front axle and as such will affect how a tire is loaded up - or not - as a car bends into a turn. Anti-dive literally will not allow weight transfer, momentarily. This is why there are really two types of weight transfer; one purely from the center of gravity and the other from the center of gravity thru suspension links.

Here is the formula:

% weight resisted by springs = 100 x (CGH - RCH)/CGH
% wieght resisted by geometry = 100 x (RCH)/CGH

I agree, anti-dive will not affect bump - compression or rebound. But it does impart an initial feeling as a car bends into a turn, actually a loss of feeling at the steering wheel and this is perceived as understeer since the tire is looking for some weight transfer as an aid to grip.

Obviously all weight migrates from the roll centers first but how it migrates to the C of G and then thru links to the contact patchs is based upon particular designs.

I'm not a fan of adding anti-dive or anti-squat or lots of caster because I feel these are a band aid for a flawed or compromised designs...but a little is acceptable I guess...and it's not that engineers cannot design a proper suspension system, they have to work within budgets. At least they know what they are giving up and what a car will for its respective use...F1 car being quite different from your Mustang or our Minis.

EDIT - forgot - Posts #36 and #46 show the PowerFlex bushing. Mine has been on my car for perhaps 120,000 miles. I removed these once to reinstall the stockers for winter...whcih I will do again because what passes for roads these days in the North East is a sorry state.