Suspension Settings & Bushings

[luvndasun]

I have a 72 911 and will be upgrading my suspension. What book would you recommended for doing the job? I would like a book that has step by step instructions and technical data such as torque settings, lubricants..etc.
Also what A-Arm and Spring Plate bushings would people recommend? I will be using the car for AutoCross and DriversEd. Are there upgrades to the factory rubber bushings that do not make alot of noise? Do the performance bushings wear out relatively quickly? Does anybody have experience with urethane bushings?
Thanks!

[Steve@Rennsport]

Hi:

Well sir, I think you'd be very pleased with both of Wayne's books at your disposal to guide you through the upgrade process. Good resources, both.

Although more expensive than some, I'd strongly recommend the Elephant Racing poly-bronze bushing setup for both your front A-arms and rear spring plates. These do not adversely affect ride quality and they are greasable (with zerk fittings) to maintain very low friction. You get what you pay for,.....

Urethane bushings do wear out and are not recommended unless you have a lathe and can hand fit them properly. If you use them, I'd suggest the installation of internal grooves and zerk fittings to aleviate the inevitable squeaking.

Remember, the quality and execution of your suspension bushings determines how successful your corner balance results will be. Suspension friction is a liability both in ride quality & handling.

[Zeke]

Hey luvin,' are you going to upgrade your torsion bars and add/upgrade your swaybars? I have a '71 and have been collecting parts for months.
You'd be surprised how much you can spend on this. And getting things to match up and work together. You can get it real stiff for track use or you can leave it intermediate for a combo use.

The interesting thing is that many claim full stiff is not the best for all track situations. So, you may be able to go semi stiff and actually have an optimum set up for some tracks. I'm hoping this theory works out for me.

Wheels and tires have a lot to do with this, too. What do you plan on in the future as far as these items go?

[Chuck Moreland]

With a name like luvndasun, that 72 must be a targa.

Steve's comments about the PolyBronze bearings are right on. He's a pro who's used every bushing product and really knows his stuff. I've got a vested interest in the product, but a search on this board will show similar comments from others.

In addition to the resources Steve mentioned, you can find plenty of how-to help right on this board. Search on "bushing replacement" or similar.

[luvndasun]

I have Waynes 101 Projects book, but I wanted to know if there are any other books such as Haynes, Porsche Shop manuals..etc that are good resources. I will be doing more than what is in Waynes 101 project book. For example I will be putting in an aluminum front crossmember and am also switching to coilovers. Are reproductions of shop manuals available at a reasonable cost?
Sounds like urethan is not a very good option for me. I just want to repalce and forget about the bushings. I'll keep the poly bronze bushings in mind.

[Chuck Moreland]

For copyright reasons, the shop manuals can not be reproduced...legally. But they don't explain bushing replacement because Porsche considers these parts non-replaceable. Their answer is to buy new control arms and spring plates, and that replacement procedure is explained in manuals.

Same is true of chiltons, bentley, hanes, etc.

These are still valuable resources as they explain the overall R&R of the components.

Modifications like coil overs are similarly not covered. In some cases, manufacturers of these kits will provide instructions. More often they do not.

I will also recommend Bruce Anderson's book "911 Performance Handbook". This is not a how-to or manual, but a good overall treatment of performance mods that have been proven to work.

You can tap a huge wealth of knowledge on this board. Someone has done just about any mod you can think of. If you can't find what you want with the search button, just post your specific questions.

There are several highly respected pros (like Steve) who freely share their knowledge on this board. There are also amazingly knowledgable amaters and racers who have been-there-done-that. You'll get solid answers to most any question you have.

[DW SD]

Steve-
You suggested the PolyBronze bushings for spring plates and control arms. Do you recommend Elephant's monoball for the rear torsion arms? Chuck, I'd throw this out to you, too?

I have the engine out and can only replace the rear arms' pivots with the engine out, correct? I can change the spring plates and bushings with the engine installed, correct?

Hopefully the answers are pertinent to this thread.

Thank you,

Doug

[Chuck Moreland]

Doug,

Cars through '72 need to have the transaxle out (or at least pulled back and down) to R&R the bolts that secure the inner link of the trailing arms. Later cars can do it with the trans in place.

I'd recommned the Elephant monoballs for anyone building a performance suspension. Their weather seals allow use on street cars while still delivering long life. Longevity was a standing issue with older style monoballs that lacked seals and would get wet/dirty.

[KobaltBlau]

what about harshness with the monoballs? my SC is mostly street (but some track) and I am trying to decide what to do for the inner banana mount and the strut tops. I'm sold on the poly-bronze for the spring plates and the a-arms, but cost is definitely a factor as well. 21/27s will be going in so it's a relatively moderate suspension upgrade.

[Chuck Moreland]

Stiffer torsion bars, firm shocks, and even low profile tires all contribute more to ride harshness than monoballs. Monoballs themselves don't have that great an impact on ride quality.

That said, if you want the smoothest ride possible use rubber.

[KobaltBlau]

That's surprising. Do the spring plate and a-arm bushings take most of the jolt out of hitting a pothole, for example, and allow decent ride quality with monoballs in the strut tops and banana arms?

as an aside, I checked the prices of the OEM rubber bushing stuff and it's not that much less than the weather-sealed monoballs.

[Chuck Moreland]

Actually, rubber bushings absorb very little of a pothole jolt. Most of it is absorb through tire deformation and torsion bars/dampers.

The force of a pothole impact is nearly orthogonal to the trailing arm (or spring plate or control arm or any other radius arm), so the impact attempts to rotate the bushing not compress it (the force Ft is tangential to the radius arm ). Because the monoball is very low friction, it rotates easily without transmitting that rotational force.

Secondary effect: Because the trailing arm is not exactly 90 degrees out from the force vector of the pot hole impact, a very small force vector will attempt to compress the bushing laterally (radial force Fr). However that same force is also acting on the tire.

The tire is a big rubber bag of air that is much more easily deformed than the rubber bushing, therefor it absorbs the vast majority of the laterall force. As a result, the rubber bushing contributes very little to the absorption of the impact.

Here is a picture illustrating all that, using a balloon to represent the tire.

[Nine9six]

There is a good article for upgrading fr. suspension in the Aug. 04 Excellence mag. Maybe not your yr. but the basics are there.

[KobaltBlau]

very nice illustration and explanation, Chuck.

Then, is the polyurethane jacket on the poly-bronze bearings primarily to conform to irregularities in the mount, rather than to provide "shock absorption" capability when a shock to the tire attempts to compress the bushings laterally?

Thanks for taking this time.

[Chuck Moreland]

Andy, yes that is the primary reason for the poly jacket. It also allows for slight misalignment in the mounts. And it's a lightweight fill for the space between bronze bearing and the mount.

[luvndasun]

I agree that monoballs are the way to go. When you are installing them, would you recommend also changing the camber plates that offer camber adjustability beyond what the factory camber plates offer? When do you want the added camber adjustability. That sounds like an option that would be best for track cars.
Thanks for all of the help.

[KobaltBlau]

Thanks again, Chuck. I had better start savin' my pennies.