Why no rubber front bushings?

Dixie · Dixie's Garage

Just wondering. I'd think it's a market that is ripe….

Why does no one make replacement rubber bushings for the front control arms? Surely it has nothing to do with the vulcanization of the OEM bushings. After all, you can buy Netrix bushings for the rear.

Why is it that if you can buy polyurethane, or bronze bushings, but you can’t buy rubber bushings?

..Just curious

blue82coupe · 03-22-2005, 03:37 PM

Smart Racing Products will restore your front a-arms, with factory rubber for about $600.00. It's cheaper... and better to install Elephant Racing Polybronze bushings. About $260.00 for the a-arms. Dan

Dixie · Dixie's Garage

No flame intended, but restoring the arms is not the question. After all, you can simply buy new arms, with bushings, for $734. I think paying the $134 difference would be worth the difference in less down time, and knowing the arms are 100% straight...

The question remains. Whydoes no one makes replacement bushings in rubber. Must rubber bushings be vulcanized to the arms, while no other bushing need be? Is there something magical about rubber bushings that makes them fall off. Or does tooling up to make them present a poor ROI?

K.B. · 03-22-2005, 05:13 PM

Stock rubber has a give or "mush" to it. Most people want to eliminate the "mush" in their suspension. I just took off my stock rubber. It did not appear to be vulcanized on - just a tight fit. I'm going with either Elephant or Mueller stuff.

03-22-2005, 06:06 PM

Damn mushy cars.....

Capt, I agree with you and was talking about this the other day. If there was an inexpensive rubber alternative, I'd certainly consider it.

Chuck Moreland · 07:17 PM

The problem with rubber replacements is the difficulty of installation. A proper replacement would need to be compressed tightly between the A arm shaft and the outer mount, and vulcanized to the shaft. All this needs to be done with the arm and mount at the proper angle to one another. If the angle is worng, the rubber will tear away when the weight of the car is on the arms.

There just isn't a practical way to do this as a DIY. Even the typical pro mechanic wouldn't have tools to do the job. My understanding is that Smart Racing doesn't even do the job in house, they job it out.

Rumor mill has it that there was to be a neatrix product for the front, it was to be DIY installable similar to the neatrix rear with little compression. The product was aborted when test cars proved to be "scary to drive".

Apparently without the vulanizing and tightly compressed installation of the original parts, the A arms were just plain sloppy in the mounts.

I speculate that solving the issue likely requires a durometer everybit as hard as the polyurethane products on the market. At that point it would no longer operate as a rubber bushing, but instead just like the polyurethane products already available.

Note the difference in operation is that rubber doesn't slide, it is bonded to both A arm and mount then deforms like a rubber band to allow movement. Rubber bushings have no friction surface. In contrast polyurethane slides on a friction surface. A rubber bushing that slides on a friction surface would perform very poorly, even worse than the lousy polyurethane products on the market. The friction would be very high and the product life would be short as the rubber wears away at the friction surface.

Makes one wonder what is happening in the neatrix rubber spring plate product! Perhaps we are simply less attuned to the rear bushing sloppiness, we don't get the direct feedback through steering wheel like we do in the front.

ficke · ficke's Garage

I do not know for sure, but my take on this issue is the bronze, teflon bushings are bearing and the parts slide on one another. Rubber bushings or not soppose to be bearings and relie on the give of the rubber for movement. Holding these rubber bushings so they will not rubb (they would destroy themself if they did) might be the issue. Weltmeister does not make a bushing for the early flanbloc cars becouse it clamps and would lock those front arms with polyurethane bushing. Interasting question that I have wondered about also. Fritz

ficke · ficke's Garage

I took to long to write and Got the ansewer after I pressed go. Thanks for the info Chuck I learned alot

Dixie · Dixie's Garage

Thanks Chuck, I figured someone knew the answer. Should have guessed it would be you. ;-)

K.B. · 03-23-2005, 04:17 AM

Chuck has all the answers.

Maybe another word about the "give" at the location of the rubber mounts. The rubber is about .7 inch from the center of the fulcrum arm. If the tire is say 14 inches out, there is a 20x difference. So even 1/2 mm of rubber "mush" would be equal to 10mm at the tire. If you've taken apart 30 year old rubber mounts you will probably see some sag in the rubber mounts from just the weight of the car resting on them all those years. There is surely a mm of movement under cornering load.

Wil Ferch · 03-23-2005, 04:29 AM

What about the 914-labelled parts that are still available from Porsche....that Bruce Anderson even admits having forgotten to mention are still available???

I guess the earliest 911 A-arms wre meant to be repaired this way...no vulcanizing. why wouldn't this approach still work on the later A-arms, using the available 914 parts ??

Wil

Mysterytrain · 03-23-2005, 05:39 AM

Chuck..I'm going to be rebuilding the suspension on my 78sc shortly. The car is street use only. My priority is comfort first and then precision following close behind. I see my choices to be few..poly fittings (harsh and prone to noise- and I have ruled this choice out), new factory control arms with rubber bushings in place (expensive, but straight and refinished/neatrix in the rear) or going balls to the wall with the ERP setup (also expensive..but the complete system front and rear gets very close the the factory rubber/neatrix solution and of course is state of the art and looks real purdy). So..can you or any of your 'rabid fans' weigh in here and let me know which will give me the less harsh ride?? Remember not a DE car, although it could happen. Stats: original torsion bars -I think I will bump those up to carrera specs or 21/27mm, Red koni's with maybe 10 years and 20 k on them, turbo tie rods, original ball joints (to be replaced) and original sway bars and bushings.
As always thanks in advance.

Chuck Moreland · 03-23-2005, 08:29 AM

Ron, the ERP 935 setup is mighty purdy, mighty spendy, and totally innapropriate for your street application. It is relatively delicate and has heim joints exposed to dirt and the elements, subject to rapid wear. It is only for serious race cars that get inspected every race with wear-parts replaced on a regular schedule - probably on an annual basis or more.

New replacement arms would work well for you, however are quite spendy.

My recommendation is to go with PolyBronze. For about $240 you can do your A arms. Ride quality and performance will both be great. Check this curent thread for some other opinions:
* Elephant polybronze bushing INSTALL -

03-23-2005, 10:48 AM

Chuck,
Do you have any data on what percentage of cars need the low friction control arm mounts along with the Elephant bushings?
Thanks,
Mark

island911 · 03-23-2005, 11:14 AM

Quote:

Originally posted by K.B.
Chuck has all the answers. .. .

Yeah, too bad Chuck wasn't around, back, in the good-ol-days, when all the other cars had greasy zirk fittings, and those crazy, low-performance-minded Porsche engineers came-up with this crazy rubber mounted a-arm.

What where they thinking?

As Chuck outlined; the idea of using rubber there, just isn't reasonable.

Chuck Moreland · 03-23-2005, 11:30 AM

Actually what I said was that a rubber replacement bushing isn't practical as a DIY installation. Rubber bushings, properly installed as Porsche did it, are fine for low performance applications.

juanbenae · juanbenae's Garage

rubber bushings are a little like wood rims on olden day cars, once they found something better, like steel or aluminum, why go back?

island911 · 03-23-2005, 11:41 AM

Quote:

Originally posted by Chuck Moreland
. . .as Porsche did it, are fine for low performance applications.

buh-hahahaha

island911 · 03-23-2005, 11:46 AM

Quote:

Originally posted by k911sc
rubber bushings are a little like wood rims on olden day cars, once they found something better, like steel or aluminum, why go back?

bunch of comedians.

"oil-changes" used to be called "lube & oil" 'cuz some "grease-monkey" had to find all the greasy zirks.

it's OLD SCHOOL

Mysterytrain · 03-23-2005, 12:11 PM

Chuck...Thanks for getting back to me. I wasn't thinking of the EPR 935 setup, I was refering to the polybronze when I was comparing the price. If I go polybronze front and rear its pretty close to new factory control arms and neatrix in the rear. But my friend...The question still lingers how is my butt (actually spine and kidneys) gonna like the polybronze!! I'm betting the poly bronze will feel better then my 27 year old rubber bushings... are they going to be harsher then new factory control arms? Sorry if I'm putting you on the spot. Also for the record what I have seen of your stuff is just top notch...major lust factor! Thanks.