QuickChange plates and the intimidation of ride height adjustment

[Tremelune]

I've spent thousands messing around with ride height and torsion bar changes, and it continues. I suspect it would have been cheaper going coilover the first time around.

My current situation is that the rear spring plate bushings on my '84 M491 make a ton of noise. They are polybronze, but I do not believe they are the ones currently sold by Elephant, as they lack zerks. I would like to swap these suckers out.

I'm inclined to do the job myself, but I'm intimidated by:

1) Bushing fitment. I don't look forward to cutting, prying, and burning these things off. I read somewhere that they might be "marine sealed" to the spring plate. I also fear I'll be banging the new bushings on (while swearing), and I don't want to be ham-fisted with my suspension. I want everything right when I'm done.

2) Ride height adjustment. I want the ride height to be as it was from the factory, measured by suspension components (not fender height). It seems incredibly tedious to index the torsion bar, get everything together, drive the car around a bit, measure, then do it all again to re-adjust.

I figure I can pay a shop a thousand bucks to do it, or I can get some help in the form of QuickChange plates and torsion bars which would make this work much easier moving forward. I think it'd even cut the shop labor down, if I didn't end up doing it myself...

Relevant ruminations:

- Alignment and corner balancing I am still unwilling to attempt myself, so this might end up back at a shop when all is said and done regardless.

- Are polybronze bushings harsher than stock rubber, or is the only real down side having to grease them every oil change to keep them quiet? That's no big deal to me, if there is no compromise in ride quality.

- Would I need the 930 "splined hub kit" for my M491?

The roads around me are terrible, and I'm rarely pushing the limits of this car in the twisties. I'm just cruising along, looking to get this car to a place where I can drive it daily in reasonable comfort.

[ClickClickBoom]

It really isn't that big a deal. I was intimidated as well, mostly its a lot of repetitive adjust measure, rinse and repeat. Adding coilovers is a slippery slope, that continues quite a way. If you need to remove the bearing surface a quality heat gun will break down the JB Weld and the race will come off. My journey:
The suspension upgrade!

[Driven97]

Wait, you're afraid of getting the OE bushings off the spring plate or the aftermarket ones?

The OE ones are easy, heat the inside of the spring plate with a torch until the rubber just starts to smoke and run a thin metal tool around the joint and they pull off like a hot marshmallow off a stick.

How hard are the polybronze press fit? Seems like a simple dremel job would make short work of the soft metal. And you may be able to get away with just a regrease and reassemble anyways rather than a full replacement.

Ride height is a snap. Use the Will Ferch calculator and angle method to rough them in to the closest spline, then fine tune with the OE adjusters. +/- 1mm here or there isn't going change the world. Unless you really get it way off, corner balance then can be handled with the front height adjusters alone.

[75 911s]

Confused. You say you have polybronze, but not the ER ones as they have no zerk. And also you are worried about burning bushings off the spring plate - The Polybronze ride on race bearings that are glued to the spring plate. So do you mean you have red rubber bushings? The polybronze have a very distinct look.

Maybe you just have red plastic ones? Like a version of this? They are notoriously squeaky.



These are the polybronze from ER



Here are the race bearings

[Steve@Rennsport]

JMHO,

If your local roads are terrible, you will never regret running rubber bushings. Thats what I use and recommend in such cases, especially on cars never used on the track! As a big plus, no maintenance is required, either.

While its convenient to make fast & easy changes to ride height, one MUST correct camber & toe each time this is done and few people have the resources to do this critical job properly. In the majority of situations, you only do this once!

Coilovers require substantial and significant modifications & reinforcement to the chassis to prevent bending and flexing. Its really not needed unless its a track-only race car where higher spring rates are needed that cannot be found with torsion bars. I strongly recommend a complete roll cage that connects and triangulates the suspension pickup points together when coilovers are used.

[Tremelune]

They were put on the car years ago by a previous owner. I was told by a shop that worked on the car that they were polybronze. I see no zerk, so it's a bit of an unknown quantity.

I had not considered the Dremel route. I got the head bearing races out of my CB350 frame in a similar way...Dremel real close, then pop them with punch and hammer. Sometimes I forget this car is just a machine like any other.

I believe this is the angle calculator mentioned: 911 Spring Plate Angle Calculator

I have added weight to the rear of the car since it was last weighed, maybe 100 pounds. I do plan to make further weight changes to the car in the future, though.

As this project evolves, the weight of the front and rear may change rather significantly. I'm trying to determine if easy torsion bar changes will pay for themselves in the future. Currently, the amount of time that I'm able to work on the car is realistically on the order of 20 hours per month, as I live in Brooklyn and the car lives in Pawling. I guess nobody can predict this bit for me, but the data is helping.

Just to be clear: I'm not considering coilovers, merely lamenting the fact that hindsight is 20/20 while currentsight is on par with being led around by a dog.

Seems like step 1 will just be to pull the retainer plate and see what I'm working with. Presumably I can do that by raising the hub enough to take the bolts off? Hopefully it'll go back on easily...?

[Driven97]

I'd raise the car and disconnect the shock so there's no load in that torsion bar, personally. I'm not a fan of potential energy.

[KTL]

Get rubber bushings in the rear. For your type of use, there's no reason to deal with the polybronze stuff. I ran rubber bushings on my '87 for years, even tracked it, and i'd do it again for a street-only car. I'd also get front rubber bushings in the A-arms. The Rebel semi-solid bushings are the cat's meow but you don't really need those.

The rear spring plate setting is not all that difficult with the factory plates. Like the guys said, use the spring plate calculator to get your unloaded droop angle set right from the very start. While you have the spring plates out of the chassis, re-index the adjustment of the spring plates to give you the adjustment you need.

Your M491/930 chassis uses the same spring plate assembly as the regular 911 chassis. Also keep in mind that if you really do want to ditch the original spring plates, because you don't want to hassle with the factory eccentric style of adjustment? You can get away with buying just the QuickChange adjustable inner plate assembly (Elephant calls it the splined hub kit) and that'll save yourself a few bucks by reusing the original outer plate.

[Tremelune]

Well. I dunno what this thing is, but it doesn't seem like its difficult for dirt to get personal with it. Maybe it got there after I removed it, though. It doesn't feel like rubber or metal.

Does the weight of the car ride on this, or should I take the spring plate off to see what's behind?

[75 911s]

Standard black polyeurethane bushings. Like the ones In my first picture above. The inside will match. These are the cheap ones that squeak (your main complaint as to why you are considering changing them out)

Upgrading to rubber from ER would be easy as you don't have to burn off the original rubber ones, as the current ones have been installed recently. The red you see is the high temp /pressure grease.

You are looking at a $300 job at least to swap them out if you include alignment.

I'd decide whether the noise is worth it at this point. The one pictured is newish and not out of round, so it's doing its job.

[Tremelune]

Indeed, upon closer inspection, these are a set of der Weltmeister 004 poly-graphite bushings. These squeaks are currently the most annoying aspect of the car, so they've got to go. I'm gonna order some standard rubber suckers and attempt the job myself, then have a shop do an alignment.

If I screw it up, it'll be obvious and correctable, so...Time to research this job. I just bought some DIY zinc-plating stuff, so maybe this is a good time to give it a shot.

I also have a set of Smart Racing adjustable sway bars that are too stiff. I like the adjustability, but I might try and get a softer bar in there, if they still make 'em...

[KTL]

Looks like those poly bushings were lubed with a typical red synthetic bearing grease. They may not have squeaked as soon, if typical poly bushing grease was used. The stuff I used was from Energy Suspension and it's a clear-ish sticky paste. WAY stickier than most greases you'll find.

Nonetheless I agree it's a good idea to ditch those polygraphite bushings and replace with rubber. I had really good results with using "Neatrix" replacement rubber bushings.

Be sure to clean the spring plate tube VERY well with solvent to clean up the grease. Then you'll adhere the new rubber bushings with super glue (cyanocrylate). Then use a lubricant like dish soap or silicone spray to allow you to install the spring plate. You need the lubricant because if you install it dry, you just can't get the rubber bushing to push into the chassis and the retaining bracket without a LOT of effort.

It's also wise to use some longer M10x1.5 screws to pull the spring plate into place. The original screws are just a wee bit too short to effectively pull the plate in place. You really have to hammer on the plate and bracket pretty hard with a heavy rubber mallet or dead blow hammer to knock it in, if you're trying to use the original length screws. Better to just use longer screws (and some antiseize paste on the threads) to make easier work of pressing the spring plate home. Once you get the assembly seated pretty close, you can switch back to the original shorter screws.

[wayner]

I've got the same bushings and same problem

I've got a bare interior and believe it or not, the squeak is louder than the engine and is in hearing damage territory

I see regular spikes into the 110+ db readings with my meter.

[BFT3.2]

If you decide to outsource your plating, I used Mid-Hudson Platers in Poughkeepsie, they did my spring plates along with a whole box of small stuff for about $60. They do car part plating on the side. They said they heat baked them afterwards to prevent hydrogen embrittlement, clarify the parts are high stress pieces. You'll have to bring them the parts blasted already.

[Tremelune]

Those look great. Any issues with threads or friction-fit pieces due to the thickness of the plating?

[BFT3.2]

Originally Posted by Tremelune

Those look great. Any issues with threads or friction-fit pieces due to the thickness of the plating?

No, none at all. But.. I installed Rebel Racing bushings that have metal races and had to have the long G50 spring plate torsion tubes sanded down on a lathe a little so they could slide all the way on. The tubes actually bulge a hair in the middle. This was all before the plating and slid on with no problem after plating.

[tirwin]

Maybe I'm late to the show but I have a few comments. I have tried doing my own zinc plating. Those spring plates are going to take a fairly decent sized setup. I had a small one -- only good for nuts and bolts. I tried doing the large washers on the motor and trans mounts with mixed results. It takes a fair amount of experimentation too. The electrolytes and current have to be fine tuned to get a good result. If the current is too high you get blotchy results. Odd shaped parts like that are hard to estimate surface area. In the long run it's probably cheaper and faster to have someone with a pro setup do it. YMMV

I always find ride harshness to be subjective and depends a lot on the rest of the suspension. Best to view all of the suspension as a system. I have ER polybronze and stiffer torsion bars and I couldn't be happier with my suspension system. It's hard to say how much each component contributes to overall feel but I suspect the re-valve work Chuck tab ER did has a lot to do with it. If you read through Craig_D's thread he talks about his experience. My setup is very similar and I agree with him. Atlanta has some crap roads because everything is always under construction and the 911 handles it very well. The polybronze bushings are probably overkill in a street car but I am not sorry I did them.

As far as adjusting the rear suspension height, the quick change system does make it go faster. It costs more, but it does save some labor. Hard to say how much. When I did my rear suspension it took me about 3 tries to fine tune. First was way off. Second was close. Got it on the third try. After the 2nd try I was regretting not investing in the quick change system.

[Joe Bob]

FYI-Going with adjustable (SwayAway) spring plates is a good idea. Tire aspect and size changes required adjustments. Easy....