rubber a-arm bushing question

[GMR911]

Hi, are the stock rubber bushings on the a-arms pressed on by the factory or vulcanized(bonded) on? Anyone know for sure? Thanks, Jerry

[MotoSook]

There seems to be a debate as to whether the vulcanize in place is a myth. Either way (bonded or otherwise), you will have to buy new A-arms or send your A-arms off to get fitted with new rubber bushings. Either is spendy, something like $400+

Check out the polygrahphite thread currently active or search the archives for all the alternatives.

[GMR911]

I was told by Smart Racing that they press fit new rubber bushings on the a-arms and they were not vulcanized on by the factory. I am considering this option but still have not made my mind up yet. My other option will probably be poly-bronze. My car is strickly street, so I am very concerned with ride quality, Jerry

[island911]

Originally posted by Souk
There seems to be a debate as to whether the vulcanize in place is a myth. .. .

debate!? The only one I know contesting the "vulcanized in place" /thinks it's a myth, is that trouble maker island911.





Sooo . ...This thread got me to go take some pix for you myth believers.







Shown horizontally here, the mold parting line gives away the tooling process.

IF the rubber where "vulcanized (cast/molded) in place" we would see a couple vertical parting lines. (else you could not remove the mold)

Also, fwiw, the rusty claw marks, above, are from where I grabbed the thing with some giant channel-locks to twist until it slipped. (not stuck to the shaft)

[Mysterytrain]

Island..I like the logic that they are not bonded in place. But I can't help but wonder why the factory [or anyone for that matter] doesn't offer rubber replacement bushings?? They have to be easier to install the the poly's and we know they last longer??

[Wil Ferch]

I think we should start using proper terms here.... "vulcanizing" is simply the manufacturiing/curing process of the rubber molecules themselves, right?...I think we're debating whether or not the rubber is "bonded" to the steel pilot shaft of the A-arm...or is it a "press-fit"..?

Nothin' to do with the molecular change that the material undergoes in the "vulcanizing" process....no ?

-Wil

[MotoSook]

Perhaps the reason rubber replacements are not available is the need to press them in. I imagine that the rubber bushings need to be compressed considerably to perform well. That is, if there is not enough compression of the rubber, they will go loose in a fairly short amount of time.

Damn trouble makers! WTF..why don't you just settle for myths and bad information so we can get on with our lives

[island911]

Apparently, getting the rubber bushings to press in often causes shop rage . .. .loudly muttered split infinitives, tools in high velocity thru the air. . . tramatic flashbacks to the first discovery that "made in China" condoms are NOT going to work.

Okay, seriously . .. Roland, wayback, pointed out that Porsche was concerned about keeping the bushings sealed tightly. (apparently roads have dirt and grit on them sometimes -Capt Obvious)

So, I see two ways to seal these. One, chemically bond; two, physically constrain. For various reasons, I believe that Porsche chose to physically constrain these.

Now, just because they go on "pressed" does not mean that no bonding takes place. It's a funny thing, adhesion . .. ya press a piece of rubber against a piece of clean steel for 10 or 20 years, and guess what?

Of note; the very old a-arm I have to play with is fairly concentric (read: no 20years of loading) .... the bushing will stick to the center shaft for ~15° of rotation. It then breaks loose, and drags, slowly, smoothly, arounfd the center.

I believe this slipping to be part of the genius of the design. YMMV

[wholberg]

Originally posted by island911
Apparently, getting the rubber bushings to press in often causes shop rage . .. .loudly muttered split infinitives, tools in high velocity thru the air. . .

Pressing an oversize rubber bushing into a metal tube will always be frustrating. This is why american cars use rubber bushings with inner and outer steel sleeves, to facilitate pressing in of the bushing, and to enable rotation inside the bushing.

Would it be practical to make rubber bushings for older Porsches with this construction?

[island911]

no descent?

[Mysterytrain]

Nah, not me. I'm dreaming about someone selling these rubber bushings. Me boiling them in water and then pressing them onto my powder coated control arms.

[aturboman]

In response to this topic raised a couple weeks ago on this forum, our company has started work on having these manufactured. We have secured a couple of new factory control arms to provide samples of these bushings for analysis and reproduction. They will be produced with the same rubber compound as the originals. I'll post info as soon as we have some idea of when these will be available, but this type of project generally takes 4-6 months before stock is availabe for sale. We do not sell direct to the public but our products will sold through retail companies like Pelican Parts if they decide to carry them. Be patient they are coming.

[MotoSook]

How will you address the installation?

[vanwyk4257]

I just installed some front poly bushings manufactured by Daystar, they were an outstanding fit, and pressed right on by hand once the proper Weltmeister lube was applied. I haven't installed the A-arms yet so I can't speak to ride quality, but I have heard the fit of the Weltmeister bushings requires some "massaging" to get them to work properly.

[Wil Ferch]

AFAIK...all of the plastic type replacement bushings will either require...or benefit greatly from.... a custom fit ( turning to a specific ID and OD ).

The problem is that you can measure and fit the ID of the bushing to the male portion of the A-arm... but once you install the A-arm, the outer "hold-down" part clamps on the OD of the bushing and distorts the precious fit you *thought* you had for the ID. Best to test fit and true the ID on the A-arm while somehow mimic-ing the clamping action of the outer, hold-down piece.

- Wil

[vanwyk4257]

FWIW Wil, We installed the rear clamps on the OD of the bushing and they fit very well. We pressed one on by hand, the other we used a shop press to finish pressing it, but it didn't take much.

[jpahemi]

aturboman:
Will you be selling the bushings or the complete arm? Will you be manufacturing your own arm or refurbishing them?
j.p.

[aturboman]

We are a parts manufacturing company so we do not get involved on the repair or installation side. The bushings will be offered to our wholesale customers and they will determine the best way to retail them. I suspect they will be offered for sale individually, but should be replaced in sets like all the other aftermarket versions currently for sale. I'm working on these at full speed so thanks for the interest.

[randywebb]

This is great news!

[porschenut]

I'm glad I decided to postpone my bushing replacement project! aturboman, you are answering a lot of people's prayers. I predict they will be a best selling item.