Suspension: rubber necessary?

[donbecker1234]

Hot on the heels of my “Coilover regret” thread, I have another question for the Pelicans.

On the original 911/930 suspension, there are several places with rubber (a arms, spring plate, shock towers, trailing arms, etc).

Just how necessary is it for these to be rubber as original to still have a comfortable ride?

I’ve seen and heard many conflicting opinions on this and would love to hear some more.

[donbecker1234]

I suppose another way to phrase the question would be: "what portion of ride quality do you attribute to the springs and shocks/struts, and what portion is deflection from the rubber throughout the suspension"?

[island911]

rubber will damp frequencies that hard joints will not.

That said, if you have torsion bars already touching metal ... anything else will seem great.

[donbecker1234]

Originally Posted by island911

rubber will damp frequencies that hard joints will not.

That said, if you have torsion bars already touching metal ... anything else will seem great.

I'm not sure if you saw that in my "advice needed" thread but yes I indeed have metal on metal back on the trailing arms.

I think in an ideal world I would have all the time to buy and install every combo of parts but I don't. I could go "factory/new spec" and just install rubber, but there seem to be many here on the forum reporting poly or even metal/monoball installs and that they didn't think the ride was too harsh.

I also see things like the Elephant Racing ASP:

https://www.elephantracing.com/porsche/911/spring-plates-for-911/asp-adjustable-spring-plate/

...making a case about how tires are different now than they were back when the cars were designed.

So...I'm eager to really hear if more people here think ride quality is more springs and shocks/struts/dampers versus rubber.

[smadsen]

The twisting of the rubber components is part of the suspension compliance. When those pices wear out (after 30+ years) the suspension squeaks and you can get metal on metal wear.

You can elect to replace the rubber bits and start over again or change over to polybronze pieces from Elephant or others. ER seems to be the most popular here. I did my front & rear 10+ years ago with ER pieces and the suspension worked smoothly and silently through the full range of motion. The torsion bar spring rates control the suspension/chassis compliance with the road and the shocks provide the dampening. Those rotten rubber joints twisting (or not) no longer interfered with the other components doing their job.

The only downside is the polybronze bushing require an annual squirt to the 8 zerks.

[donbecker1234]

Originally Posted by smadsen

The twisting of the rubber components is part of the suspension compliance. When those pices wear out (after 30+ years) the suspension squeaks and you can get metal on metal wear.

You can elect to replace the rubber bits and start over again or change over to polybronze pieces from Elephant or others. ER seems to be the most popular here. I did my front & rear 10+ years ago with ER pieces and the suspension worked smoothly and silently through the full range of motion. The torsion bar spring rates control the suspension/chassis compliance with the road and the shocks provide the dampening. Those rotten rubber joints twisting (or not) no longer interfered with the other components doing their job.

The only downside is the polybronze bushing require an annual squirt to the 8 zerks.

Do you feel like polybronze made the ride any more harsh than rubber would have?

Any reason you wouldn't/didn't consider metal/teflon instead of the polybronze?

https://www.rsrproducts.com/product-page/rebel-s-racing-rsr-rear-bushing-set

[island911]

Rubber provides a compliant, no maintenance, dirt and grease free solution.

The plastic bushings provide a somewhat compliant low maintenance solution.

Bronze are are a non-compliant high maintenance greasy mess - antique tech.

[donbecker1234]

Originally Posted by island911

Rubber provides a compliant, no maintenance, dirt and grease free solution.

The plastic bushings provide a somewhat compliant low maintenance solution.

Bronze are are a non-compliant high maintenance greasy mess - antique tech.

Yes, I think I understand those differences. The reason I started this thread was to collect opinions on how much of ride quality the members here think is due to the rubber or to springs/shocks/dampers.

I'm looking to replace all the old rubber on my suspension, and if moving to poly and/or metal makes my suspension perform better without compromising comfort in any significant way, I'm all for it.

If switching to poly/metal means my wife and/or kids will be uncomfortable with the ride, then I'd just stick with the rubber.

[island911]

The frequencies that the rubber decouples won't be the bumps so much. Think more about road noise spectrum. relatively small amplitude stuff.

[donbecker1234]

Originally Posted by island911

The frequencies that the rubber decouples won't be the bumps so much. Think more about road noise spectrum. relatively small amplitude stuff.

So if moving to poly and/or metal to eliminate rubber was paired with using some sound deadening such as Dynamat, do you think passengers wouldn't notice?

[island911]

That's like saying you can leave a window open in the winter because the car has lots of insulation. (so it keeps the cabin warm)

The suspension pickup points are on rigid steel. That steel will transmit "noise" (vibration) very well. Read right past panel insulation.

[RWebb]

How comfortable a ride?

[donbecker1234]

Originally Posted by island911

That's like saying you can leave a window open in the winter because the car has lots of insulation. (so it keeps the cabin warm)

The suspension pickup points are on rigid steel. That steel will transmit "noise" (vibration) very well. Read right past panel insulation.

Just reread your previous post and it sunk in. Thanks for the patience on the questions.

[island911]

Yeah, Dynamat it there to help block noise coming thru the air. -fluffy soft air. Often much from tire tread singing over grooved or old exposed aggregate surface. Now imagine you have a metal path directly from the noisy tire to the cabin. You feel it in the steering wheel and the shift knob first.

Porsche put rubber bushings even in the steering linkage. The Turbos did not get the tierod rubber.

It all comes down to how much feel do you want? Too much and it becomes obnoxious to make much of a road trip. These cars are not Cadillacs, and they are not go-carts either.

If you think that Race Car is the goal, remember, race drivers get paid to put up with that punishing ride quality.

[donbecker1234]

Both the Lotus Elise and the Exige 240 I had didn’t bother me road feel or even road noise wise.

It was the harsh suspension that got me as the miles racked up, which makes me think it’s all springs and shocks/dampers.

['78 SC]

I firmed up the suspension of my '78 for track use: polybronze f/r, spherical trailing arm joints and Wevo engine/trans mounts.

I installed the front polybronze first and noticed no change in noise/harshness. There was a noticeable increase from installing the spherical joints. The engine/trans mounts increased cabin noise (especially higher frequencies).

I am decommissioning the car from track use and have swapped in softer inserts in the Wevo mounts. I intend to replace the spherical joints with stock units. I will keep the polybronze bushings front and rear.

[famoroso]

Originally Posted by donbecker1234

Both the Lotus Elise and the Exige 240 I had didn’t bother me road feel or even road noise wise.

It was the harsh suspension that got me as the miles racked up, which makes me think it’s all springs and shocks/dampers.

I concur with that. I replaced all the rubber bushings in my Elise track car with sphericals. Surprisingly, the sphericals didn't come with much of an NVH penalty. The Elige is a different animal though, with a thoroughly different baseline than a G Body. Although, replacing the OE Bilstein sport suspension with Nitron double adjustable shocks and significantly stiffer springs actually seemed to improve the ride quality (at least at the softest shock settings). Anyway, back to G Bodies...

I have a 60k mile '88 491 cab (the wife friendly fun car) with Bilstein HDs all around, ERP 935 steering tie rods / bump steer kit and new OE hardness rubber spring plate bushings. At the same time, Jae Lee (Mirage International) bump steered the front suspension, corner balanced and aligned. The car drives, and rides, beautifully.

I'm currently building a mildly wife unfriendly M491 "Club Sport" coupe, of sorts (among other deletes, no radio / stereo or speakers, etc). It's a sports purpose street car. I'm sticking with the stock M491/930 torsion bars, going with new OE hardness rubber: in front A arms, upper strut mount, rear spring plate bushings and sport hardness rubber trailing arm bushings. Also, ERP 935 steering tie rods / bump steer kit, M637 Club Sport (and, interestingly enough, Cabrio) engine mounts. On the flip side, we're doing KW V3 double adjustable shocks and struts (with 19mm raised spindles) and an Eibach Anti-Roll-Kit. The goal is usable / adjustable (compression, rebound and anti-roll bar settings) performance with minimized downside (NVH and maintenance). Kicked up road holding / feel / performance a notch or two, without compromising long distance road trip or road rally usability. I'm leaving some performance on the table by going with the rubber bushings, but I'll err on the side of comfort for a street car.

[GH85Carrera]

Much of the opinion of what is the best option is a personal choice. My 1985 911 had worn out rubber bushings. I replaced them with the Elephant Racing new rubber bushings and did the other typical things of Turbo tie rods, new ball joints and new Bisltien HD shocks. I really love the improvement and I think it was perfect.

I have ridden in and driven other 911s with the plastic or polybronze bushings. Those are great for a track dedicated car, but I personally thing they would suck big time for street driving. They were very noisy, and harsh.

Your best bet, join PCA, go to some events, meet the other guys. I have several friends with SCs and Carreras that are street cars. Get a ride in those cars, talks to the owners. Make you decision with that information.

[chrismorse]

If the condition of your local roads is “some ok, some terrible”, I would stay with rubber for a driver and not go much stiffer on the bars, springs.
I went with automotion polyeurethane bushings on my old hot rod 914 and they were very rough on the street, primarily due to their inability to relubricate and the subsequent “stiction”.
That said, I rebuilt the suspension on my 308 and used “poly-graphite” bushings and doubled the spring rate. 20 k miles and it rides ~~50% rougher on our humble county roads.
The 74 will only see occasional DE events, so it has Elephant rubber.
Another option is to go with “sport hardness”, or heavy duty rubber. This may give you a bit less compliance, but still offer some road noise reduction.
(Elephant only offered sport hardness for the strut tops and the trailing arms, so, I went with those. The car is not on the road yet).
No experience with monoballs on the street.
chris

[island911]

Some good posts there ^

If you are even considering adding Dynamat for ride/cabin comfort then stay with OE rubber pivots.

Rubber pickup points will be a MUCH lighter and more effective solution than Dynamat.