Ya. I shouldn't have said many. Has been a while. But I do recall the band saw really hating it.

What I'm not sure that I'm understanding is whether or not the surface of the bushing moves slightly relative to the housing/shaft when the suspension settles.
I can see two schools of thought...a racing type of bushing (solid) which obviously allows free movement...and the rubber/poly that creates resistance to movement.
Ignoring the considerations pros and cons of vibration, changes in handling, etc. what would be the downside of bushings that move freely, assuming a stiffer spring and a shock with slower compression/rebound valves were used (my understanding is that the bilsteins have more resistance to compression and slower rebound....i think). It seems to me that allowing the spring/shock to provide all control over movement of the arms would be preferrable....but I can't really think of a situation to think through to illustrate. I'm not saying a that zero resistance control arms are better...just curious about the theory behind relying on resistance from them vs offloading everything to the spring/shock

"what would be the downside of bushings that move freely"
You could spend 4-5k on proper springs and real shocks...and have a solution, that still doesn't replicate the OE design, there will be tradeoffs, at least without a lot of expert thought put into it..and a LOT more $ than this.

And that'd the neat part, the bushing is spring, in both directions.


Where is your rebound spring rate once the chassis is _above_ level ride height? I don't know anyone that makes a spring to pull a chassis -down-...

It's a GT car, 911s are race bred cars (right tool for the job kinda thing)...it's a huge rathole to overthink that the 928 is, and what you think it should be. Respectfully..there are no wrong decisions, just..how does a thing improve on what was provided you already.

I believe Greg's working on such a suspension, and it wont be some over the counter springs and badly matched single adjustable shocks.

What those bushes do, is very hard to do otherwise, without spending multiples over what just a rebuild set of arms will do for the car. A set of new M474 option shocks (that you can still get) and a bushing refresh on the car as a WHOLE is cheaper than a competent new spring and shock package to use a rotating bushing (That probly wont last 30yrs, which is what we are comparing against)

I need to understand stuff in my mind - just my nature, I don't understand this bushing design and philosophy at all. The object of suspension is to be able to move - absorb, rebound, articulate, react, etc and the stiffness should be controlled by the spring and the dampening should be controlled by the shock. Having control arms that can't freely rotate adds stichtion to the suspension where it not only resists rotation on the compression stroke but also resists rotation on the rebound stroke - I can't think of a single way that's a benefit for a suspension to do it's job and taking this to the extreme would mean if you had so much stitction or resistance that the suspension would never even move, that would be better, but we know it wouldn't..

The biggest upgrade people make in 914 and 911 suspensions is to use roller bearings on the front A-arms so that there is essentially zero resistance to the arms free movement, allowing the suspension to react to the road without being compromised by the A-arm not wanting to rotate. Why is the 928 suspension any different in this regard?

You are challenged by thinking how it "should" work...because 'thats how everyone else's works'.

Not how the unique 928 bushing design actually does work.

The LCA most certainly is able to freely move..just as a secondary spring. You forget that a "normal" suspension vehicle does not have a freeeeely moving LCA, it's tied to a spring as well.

It's also a spring, that works both ways. A coil spring cant do anything about capturing rebound...these bushings can.

You can also have the benefits of a linear spring, and a progressive rate spring in the bushing that only exists when you need it...but you dont have to have a HAMMER of a stiff main spring to get all of this usable spring rate either when you DO need it.

Our LCA isnt just tied TO a spring, it is also a secondary spring that works in an entirely different manner to compliment the linear coil spring.

It's also a lot less road vibration as well, as everything is sitting _in_ rubber, not in a steel collar rotating with a bushing assembly...


"The biggest upgrade people make in 914 and 911 suspensions is to use roller bearings"

Entirely different vehicle use cases, and a step backwards in already limited long drive comfort. Those are not GT cars, the 928 is not a race car design evolution.

Keep in mind that Porsche decided, for safety reasons, that every single car they made should understeer anywhere over about 60% of the final adhesion limit of the tires.

This philosophy of handling ensures that the vast majority of drivers (who were not trained in 911's), could lift off of the throttle, resulting in the front end "biting" and the vehicle "turning in".

While not the fast way around any corner, this made the legal department much happier, especially after the 930/Laguna Beach lawsuit.

In the 928, the progressive nature of the lower control arm bushings ensures that as the car leans into a turn, the resulting spring rate of the spring, the rising rate of the bump stop, and the rising rate of the lower control arm increases significantly faster than what occurs in the rear....ensuring understeer.

Pretty darn clever engineering, for the time!

This I found after a quick search :

Originally Posted by McClellan Law
Speed and Power Defects
The McClellan Law Firm has litigated two cases against Porsche involving the Turbo 930, in which the combination of power, turbo-lag and oversteer made the vehicle too difficult to handle for the average driver, without proper warnings and instruction.

The first case, Garrison v. Porsche, arose out of the death of a husband and father who was a passenger in a Turbo 930, when the driver lost control on a city street and went into oncoming traffic. The jury awarded $2.5 million, which was upheld on appeal. The 1983 award tied the verdict for the death of Audie Murphy, a war hero and actor, for the largest wrongful death verdict in the state of California. Following the Garrison verdict, Porsche started offering driver's training to the purchasers of its high-performance, turbo-charged vehicles.

The second case, Trent v. Porsche, arose out of the death of a husband and father, when the Turbo 930 oversteered and collided with a telephone pole. The case settled for a confidential amount.

So my question :
are this changes coming to the 928 with the big brakes in 1986?
The S brakes are from 1980 there or was it a feature from the beginning of the 928.

I completely agree with this. But it all depends what you want from your car. Do you want it as Porsche intended or something else.

I did install the Power Flex LCA bushings and they allow complete freedom of movement and have almost no resistance.

I cant see or appreciate the value in the Porsche OE design in this area. Anecdotally... before I installed the power flex bushings I disconnected my front sway bar and went for a drive. Then I pitched the car over into a turn. It tended to stay pitched over and took a set for a few moments, kind of like when you jack up the front of a 928, it stays up. This was Odd to me to say the least, not what I wanted from a performance car. That laziness or lack of responsiveness was not what I wanted and so at that moment any reservations I had about installing the Power Flex bushings was gone. After I installed the PF bushings the difference in responsiveness was very noticeable and more inline with what I wanted from my 928.

I'm not fully accepting of the "significant spring rate" argument regarding the OE Porsche bushings becasue of my first hand experience. They clearly do offer some spring rate but I was able to to move the OE bushed LCA while it was free of the spindle by hand with modest effort along the range of travel that the shocks allows. I dont consider my personal arm strength significant when compared to a automotive spring. I think they mostly offer Resistance and posses a diminishing reaction function. I'm not fan that or of this design. There is a reason ZERO other OEM's used this design before and ZERO have used it since. That tells you all you need to know about it's virtues.

As for roller bearings in the Suspension I have 2 Jag's and a DB7 GT rear suspension that utilizes needle roller bearing at all the joints in the rear suspension. The level of clarity, responsiveness and communication you get from this is under appreciated. That inspires confidence and is more in line with what I expect from a performance vehicle.

'I was able to to move the OE"

How old was it?

"There is a reason ZERO other OEM's used this design before and ZERO have used it since. That tells you all you need to know about it's virtues."

No it doesn't.

Going down the path of a track car, has zero bearing (no pun intended) on the OE design or use case.

Thanks for the input. I'm going to install the Powerflex kits on the lower and see how I like it. I'm thinking I'll like it just fine since I'm a sports car guy and find an original 928 too soft on many fronts - seats (swapped to 991 hardback sport seats), suspension at OEM ride height (dropped front and rear and prefer the sport springs), larger 18" wheels for less sidewall flex than OEM 16s with tall sidewalls), and am going to install Hans' adjustable drop links at some point too.

I'll report back how I like them once installed.

What spring? If you have adjustable perches you can cut the springs to get some more rate. After some carefully considerations, I cut 1 coil off the fronts and 2 off the rears as a stop gap measure. Then I looked and waited awhile (2 years) to find a set of Weltmeister springs. During that time I rode around and did some DE event on the cut springs. After I installed my new found Westminster's and much to my disappointment there was No meaningful difference in response or performance that I could tell between the cut OE springs and fresh Weltmeister springs. The WM's do look much better with their fresh powder coated finish so I'm happy to have them none-the-less.

I'll have to look. Think they're the blue dot sport springs or might be the double brown dot - can't remember which are on which 928.

As suspension technology evolved, Porsche was able to "free up" the lower control arms on their cars and not continue to depend upon the "928 design" to induce understeer.
Progressive springs can do the same thing. You just need a computer or a lot of spare time to figure out what rates you need.

928 handling and suspension discussions are almost a waste of time, without knowing basic ride heights, type of shocks, bushing condition, and bump stop condition.
For instance, the bump stops on the shocks, really confuse any discussion or comparison without knowing some of the above:
A 928, without any other changes (except alignment), is a whole different handling vehicle at 170mm ride height versus 150mm ride height.

We repair, restore, and build an amazing amount of 928's.
Suspension choices and pieces are a variable that is only solved, after a discussion with the client of their desires and expectations.
What is perfect for one client, can be a nightmare for another, if you are not careful.

For example, our pure "street/weekend canyon carver" suspension development focused completely on the NVH of the cars.
It was simply not acceptable, for us, to trade one of those parameters for another.

NVH?
I find the solution on the Iris blue restauration nice.