It was my understanding that so-called "anti-dive" suspension geometery's effect were to 'slow' the inertial forces that lead to what is refered to as weight transfer - to look the other way think RWD drag car, where a rear biased 'weight transfer' is desireable, soft rear springs allowing the car to squat and bite better - IMHO your second paragraph contadicts itself, but maybe I'm not understanding the wording: It could not be only a function of geometery if it was not tied directly to the C/G, which changes based on the movement/direction/speed of the vehicle (the so-called "polar moment of inertia"), correct?

 

is a function of the mass distribution of the car. It may change a bit as suspensions do thier thing (or a lot in the case of a dragster doing a wheelie), but really it's a function of mass distribution.

meb, I think we're goint to have to agree to disagree on this one. (but one of us is right!). there is merit to the perception about car dynamics as suspensioins do what they do, and that these motions can be usefull in providing feedback to the driver, but you saying that anti-dive/anti-squat doesn't effect bump rates contradicts completely that these suspenions designs momentarily "lock up" the suspension. It's this phrase that I don't agree with at all. It is also this phrase that self-propogates as one of the worst descriptions of anti-dive/anti-squat suspension geometries. There is no lock up, there is just the net effect of induced forces.

Funny story on the perception of car dynamics. Mercedes has been putting some active suspensions into the high end cars. One of the first, I think, was the 09 SL series. Anyway, the car stays totally flat through turns, and this isn't what most expect, so it feels wierd. Cut to the 2010 model year, and the S63 AMG (a monstor of a battleship if there ever was one). Anyway, they now have "active bolsters) that inflate the side on the outside of the turn. This gives back some of the dynamic feel of the car lean (even though it doesn't really). Thing is, the system is effin' slow! So you go through some fast esses, and at some point I guarantee that wrong side of the seat is inflated. The feeling totally sucks. Thank god you can turn the system off. Too bad that in the short time I got to flog the S63 I didn't know how. The system sucks for spirited driving, while it might be good for slightly fast driving on the streets or whatever. In my mind, it's just more expensive crap to break on the car.

Matt

 

Pure weight transfer and pure bump are two differnt things, yes?

When a tire hits a bump the suspension compresses...this has nothing to do with anti-dive because there is no weight transfer involved.

When braking or when trail braking into a turn or when weight is transfered during the initial stages of a turn anti-dive imparts a feeling of vagueness because the anti-effect is not allowing weight transfer. My stick analogy is not good, but the suspension definately locks up momentarility because it is not allowed to suspend - the springs and dampers are mementariliy locked out of operation...else the anti effect doesn't work.

LATE THOUGHT: The stick analogy is not good because it implies a stick has replaced the strut and this will cause an immediate slide because all of the weight has transfered to the tire at a near instantaneous rate. The anti effect reduces weight transfer.

 

Matt,

I went back to miliken and my own notes...I don't do this stuff often enough - and I wrote this correctly before.

Anti-dive does affect bump and one of the other reasons other I don't like it. Since suspesnion movement is geometrically limited by the anti effect it acts like a stick when the tire hits a bump. I should have thought before writing since the very same motion - dive - is the same motion as bump. Apologies Matt.

However, my original point, and we're way off the OP's question, is that anti-dive will reduce weight transfer to the front tires because it will not allow weight transfer. This will impart a vague feeling at the steering wheel that feels like understeer...actually a loss of grip. Off throttle response is actually quite bad with the Power Flex bushings due to anti effect, but on throttle grip and steering response is spectacular...so I guess these keep one honest by keeping us on the throttle.

 

http://premium.nascar.com/2002/TECH/...ive/index.html

Ah... Aren't internet forums grand?

Matt

 

That's a good write up...not too technical.

Again, apologies Matt.

 

is that circle track guys set up a really wonky suspension, and get around the track faster! Real black magic, that....

Matt

 

OK, then.....


So, I went out today, got the MINI up on jackstands, and pretty much checked all the bolts (sizes, and for seizing), all seem OK - lined up all the right tools - just waitin' for parts and decent weather (important for those of us without garages ) - will try to photo the process, and vid the "action" of the 'Power Flex' bushing...

 

I finally got around to watching your video. Pretty good work. What's more worrying than the spring rate change is the friction. While it takes 60-80 lbs to get to full extension, that's only 20 or so lbs/in delta, stiffer than stock by around 10+ %. Not that big a deal. But what is worry some is that a) it appears assymentric and b) it seems to have a lot of friction. Now THAT's worry some.

The stock part does describe a bit of an arc with no fixed pivot point anywhere along the trailing arm shaft (at least that's how it looks in the vid, I may be wrong there). The Alta PSRS fixes a pivot point by using a delrin ball, but I fear that to keep it tight it exerts some frictional forces. I'd guess that it's a very low number compared to the torques present when actually driving a car. But it does look like it eliminates the arc-like motion of the stock bushing. Does this really matter? I have no clue.

I'm guessing that the multi piece polys were designed so that the inner part could rotate, and the use of different elastomers was to signifcantly reduce the effects you're finding with the baviarian auto parts. I guess as others replicate your tests, we'll get some data on that as well.

Overall, a real good job!

Matt

ps, damn! I had a set of these I found in my garage that are now in the marketplace.... Guess they'll be there for a while....

 

If the weather is good, I will remove the lower ball joint and tie rod so I can shoot a short piece showing the movement of the LCA with the Power flex bushing installed.

I have but one problem...I don't know how to get a movie into NAM computers don't like me and I don't like them.

Matt, your description of the two piece is spot on. This is in my opinion a great bushing. But I am no longer tracking the car and the roads are terrible this year...and my fanny dyno is getting old, so something a little more forgiving is in order.

What I like about Power Flex:

I get super steering response and on throttle tracking thru a turn is amazing.

What I don't like:

Some anti-dive affect for reasons pointed out above, and though these are a little harsh in summer, they are near intolerable in winter...I'm assuming the poly gets harder as temps fall. These bushings also have a little bind at the extremes of travel and need to be lubricated at least once a year requiring a sub-frame removal.

Greg's LCA eliminate all of the bad while incorporating some nifty adjustability. Are you thinking about a street version Greg?

 

Good comments,
Michael, I look forward to seeing what you come up with in a movie.
Matt, you are absolutely right about resistance within standard suspension travel. A better test would be if I put a scale on the arm and gave it a good hard quick push down only about two inches. I think, think you might find that the resistance to be even higher then what I state in the video. I'll look into a beter way to actually test this.
I'm not sure that the alta changes any motion in the slightest, but rather it just caters to it better then most.
I will put up a short vid of what I was using on my race car. As close to zero disruption as about possible.

Michael, as far as street the issue is liability. In the past there have been others who have already threatened suit over this same replacement part failing. Just don't think it's worth the hassle. But, I will tell you that my suspension upgrades are a dramatic change for a car that has been lowered and had track type suspension mods. We will see what happens down the road. Jason is putting plenty of HARD road miles on my system. Jason, feel free to speak up.
Also, so much has been talked about the front that I did not mention the back. This part is the very first for the Mini to correct rear roll center and mostly anti-dive. Haa, there Michael. The front is also adjustable in track, camber, caster, roll center, and anti-dive.

 

Okay.

On smooth roads, onasled's new parts aren't that bad. For those that aren't familiar with my car, it's a Cooper on coilovers with a rollbar, gutted back half of the car, race seats, no hood insulation / liner, no radio, no A/C, etc, etc. So, "comfortable" is relative.

The ride of the car was much better with the new parts than with the old stuff. The "bad bushing" in Greg's video was on my Cooper before the new parts went on. Once the coilovers were installed, I noticed some bouncing / oscillation when the frequency of the bumps in the road were just right. With the new stuff, on the same roads, I never noticed this.

The noise of the new parts is slightly alarming. Hitting expansion joints, etc is loud.

On bad roads, it's bordering on miserable. I drove from Burlington, Vermont through Montreal to Le Circuit Mont Tremblant. Going through Montreal involves a long bridge to get onto the island, so lots of nasty expansion joints. Then, through Montreal the roadway is concrete with lots of patches. And between Montreal and Tremblant, the pavement sucks. The ride might not have actually been that bad, but the noise was bad enough to make me wonder if everything was going to stay together. Of course it did, but it was not a nice trip at all.

So, besides the liability issues, you'd have to be a glutton for punishment to want this stuff on a street car if the pavement isn't really good.

 

You must be hearing impaired after that ride. It's no pleasure on the roads up to Tremblant!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

One of the finer points of suspension design, rising only to conversation level for folks like us, is the frequncy at which uncontrolled springs work. Those being springs, tires AND bushings but not all.

The bind noted in Greg's movie is astounding to my eyes but what might be worse, pointing to Jason's comment about bouncing, is the unsympathetic frequency introduced by this bushing...frequency here meaning the rate at which this bushing oscillates in addition to its spring rate. Attempting to keep the tires, springs and now bushings all in sync at each corner and then front to rear is a headache waiting.

I have one image of this bushing forcing the tire into bump at which point there may be a sudden loss of traction...

We may find that Power Flex and Alta figured this bushing out for the street, but that Greg's is the piece for the track...not a bad place to be actually.

Maybe we can get Matt to unhook his ball joint and tie to illustrate the Alta unit in operation??? Hey, if i have to jump...

 

I want to see images of onasled's handiwork on a car. Reengineering a suspension is pretty damn cool.

 

We're still working out the bugs... no pics until it's ready... "we'll sell no wine before its time" or something like that.

 

That is exactly what i'm thinking...the two piece bushing would definitely allow for more rotation than the Bavarian Autosport ones. Looks like I may have to make a change.



Nice presentation, Greg. How about forward me the plans to the ones in the race car so I can whittle me a set? ...

or

...if you're changing to the new setup on the race car, let me know if you want to get rid of the bushings in there now.

 

Joaquin, problem is that the custom arms have to be used with my monoball set.

I'm still not sold on any two piece bushing being better by design then the single piece as far as rotation goes, as "rotation" is neither the main motion nor the issue in binding. I think that the two piece may be better in choice of material rather then design.
One reason I'd like to get my hands on a set to test, or see what Michael comes up with in a video. I'm betting the you won't see the inner bushing move against the outer.

 

I'm telling you all, the inner bushing rotates within the outer bushing and when the control arm is lifted to its highest point - with a finger tip I might add - it will drop and contact the sub-frame.

The inner sleeve has a hex shape to fit over the hex LCA stud so it moves in sync with the LCA. The outer bushing remains stationary...from the rear you see the movement.

I am not taking the sub-frame off for this video, just removing the tie rod and lower ball joint to illustrate freedom of movement. From Greg's video I would say the Pflex bushing is light years ahead of the Bavarian bushing.

 

I'll wait and see. I'm just not getting how the powerflex could be that much better. Yes, softer material means less binding, but then you get more slop. I can't believe Michael that you can move these with such ease, which is why I can't wait to see the video. Haaa. I never say never, ...
Better be good movies Michael!

 

I know several folks here running the powerflex bushings... and all are very happy with the improvements in handling... and none have reported any binding... but that worthless hearsay is all I know about this...

 

True...but, I doubt if anyone on here that has them moved the control arm to full compression and rebound(like Greg did in the video) before putting everything back together.

 

I'm gonna start wonder about IQs shortly...you can read above or...my sub-frame has been off six times since installing these bushings. I pulled the sub-frame off to clean and re-lubricate the Power /flex bushings and replace inner tie rods and inner ball joints. The LCAs move with greater ease than the stock bushings until just short of full travel in either direction...this bushing moves in and out in the process.

Greg...good movie...mine will be different, I'll be nude...dunno what the hell that is I keep tripping over

EDIT: The IQ thingy above is a tease, and wasn't meant to be mean spirited...unfortunately this type of communication omits facial expression and also lacks the cadence in a typical conversation. Apologies if taken the wrong way...

 

EDIT: I doubt if anyone on here except for meb has moved the control arm to full compression and rebound like Greg did in the video before putting everything back together.

Sorry Michael, I did read your thread about cleaning/lubing your bushings, I just forgot.

 

Ahhhh, ... don't worry about meb. I see the time on his post and figure he's already been in the wine cellar.