Rear Lower Stress Bar Feeler
 

After doing a lot of digging, I found the "Pedro" bar, the Ranntech bar and the "Bristol" bar, but all of them have certain deficiencies that I wanted to avoid in tackling this item. Specifically the issues I found were price, effort of engineering and quality of materials. All of which I believe I have alleviated in the development of this piece.

I present, the new and improved 986/987 lower stress bar.

The kit;

http://i68.tinypic.com/2py49px.jpg

Components;

http://i66.tinypic.com/2s76no1.jpg

And installed;

http://i67.tinypic.com/2cqn34i.jpg

The main differences in this kit is that the attaching bolts are all hardened with hardened bushings that can handle the loads of the stress that can be placed on them and the hardened Heim joints with a thicker end wall which has been tested to over 90,000 lbs of load before failure. Plus since the bar is adjustable you can actually pre-load your rear toe and/or camber slightly, (more is available if you modify your aluminum plate). The bar itself is made out of 1" aluminum and is IMCA appproved. The Heim joints are Carbon Steel and zinc coated to prevent rust, I found that the bearing joint is not necessary and actually added another possible point of failure, therefore the solid Heim.

Initial impressions are a tighter rear feel with less oversteer and firmer ride, but a definite improvement over stock.

These kits are available for $97.50 + shipping. PM me if interested.

Where are you installing the flat washer ? Under the bolt head or between the flat of the heim joint and the suspension ear ? I assume you are " pre adjusting " towards the outside then installing the aluminum plate ? A little more detail please . Thanks

The washer goes under the bolt head to prevent galling of the bushing and the heim joint. As far as pre-loading, I initially installed it nuetral, but I will be playing with it once I get to the track. I want to get over to the alignment shop and see what the best setting would be.

I have a version of the Pedro one made of hexagonal Alu. As much as I like the thought and look of your bar have you not overthought this? Mines been on for 4 years or so and doesn't appear to have had any issues.

"Overthought"? Maybe, I tend to do a lot of over-engineering. In my past I worked at a fabrication shop building everything from headers, to rollbars, to entire tube chassis, so yeah, I will build something to perform beyond it's means. Besides, it's for a Porsche, has anyone in Germany ever told Porsche "you're overthinking..." ;-)

I looked at the Pedro bar, and quickly thought, "for the price I can do better". The Pedro bar is fine if you just want to stiffen the stress points, but I wanted something better with some minute adjust-ability. What I saw first with the Pedro bar was there was no room for error between the attaching points, I read that some users had problems lining up the bolt holes...

Any thoughts of installing " flats " on either end of the tube to allow a wrench to turn/adjust vs. the knurled section you currently have ? I picture the car being on an alignment rack with the holes in the aluminum plate being slotted . Loosen the nuts/bolts on the aluminum plate and now adjust with your cross bar to whatever alignment spec's can be achieved . Tighten down the secondary nuts on your bar and then tighten down the aluminum plate hardware . Is that the general idea ? I'm thinking turning the bar with a wrench vs. your finger tips on the knurled section would be easier . Just thinking out loud .

Not a bad idea, however the wall thickness of the link tube would probably be greatly compromised if there were "flats" put into it. I suppose an alternate could be to weld a pair of nuts on the ends of the tube. I used jackstands when I installed mine and had no problem turning the tube by hand.

I don't understand how this bar or at the Pedro bar improves stiffness. Aren't the two sides already prevented from moving through the aluminum undertray?

While the aluminum undertray is there to do just that, it has a tendency to flex under strong loads, even bend. This bar alleviates that possibility.

Thanks for the explanation. I'd be surprised if a 2.5l can generate enough stress on the suspension to cause the tray to bend. Maybe a good solution for S cars.

The particular stresses are not related to hp, but are rather a function of cornering loads.

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I dunno, never owned or drove a 2.5, but I would imagine that if you drove it hard enough you could cause some damage.

Exactly! It's about how well do you drive your car.

Please post your results/thoughts after you hit the alignment shop do you think you'll be doing that soon ? I am interested in your product . Not sure how many others are interested but a " group buy " might get the ball rolling :D

Possibly this weekend.
And yes, a group buy would get the ball rolling, even save some $.

I'm interested, but also very interested in what the alignment shop visit produces.


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Capitalism is a great concept, but all these parts can be obtained from Rod End Supply for about half that.

Well aren't YOU just everyone's best friend? hahaha.

Personally, I don't mind paying somebody to do the research for me on what size, length, etc for the rod ends, plus the tie-rod, plus provide the hardware. then assemble it all into a kit for me, so that I can simply ORDER it, and then INSTALL it.... without worrying if I ordered the wrong one, waiting to see if it'll arrive correctly, hoping that the bolts I sourced are correct, etc etc etc.

And I know that personally, if I were offering a service / product on a forum and you hijacked my thread to tell everyone how to get my service / product without me, I'd probably wish you had started your OWN thread about it.

but that's just me, and my sense of decency.

Is this "confirmed"? Do we know that it flexes and do we know that there is a real gain by using the stress bar? Comparing with a front strut brace which I believe is considered redundant..

EDIT: Not trying to sound negative, I want to believe... ;-)

I agree with you. Certainly you have a backend investment of time associated with the development particulars for the part. I recognize the value ($$ - time being money) in that effort. Personally, I commend you.

Further, anyone could source parts to fabricate half-the stuff "sold" upon these forums. That's the easy part.

Keep up the good work. Thank you.

I'm not quite seeing the relationship between the quality or performance of the bar and an alignment?

You can also go buy an aluminum bar from anywhere, mill the ends, source the attaching hardware for about 1/3 the price, but then again you will have to have the tools/mills to do the machining required, and the time, and the skills...

Like I said, I have been doing stuff like this since I could crawl, I had a hammer in my hands at age 2 and have been turning wrenches for over 50 years now so If I am offering a product, I know it's going to be a superior product that will never fail. But if you want to build your own using parts from Rod End Supply, go ahead. But I have already sourced the items, done the homework and verified fitment.

Are the rod end threads reversed so you can adjust the length while on car by rotating the tube?

A stock alignment keeps everything in a correct relationship for proper street performance. I mentioned a trip to the alignment shop to see what changes with the adjustability of this product. From what I can at this time only imagine is that we would be able to dial in/out some camber or toe for track use. Once I get on the rack I will be able to verify.

Yes. And due to a previous request I have contacted the manufacture to see if "flats" can be placed on the tube for a wrenched adjustment. But the tube rotates easily by hand with wheels off the ground.

Which front brace are you referring to?

MG do you think the aluminum plate will have to have the mounting holes slotted or " opened up " to allow suspension adjustment ? Or do you think there is enough " slop " in the holes from the factory ? You will know more once you get alignment rack results just curious on your thoughts and what you have seen on your own car .

I just used some aluminum rod stock and drilled holes. Preloadimg this stuff is pointless in my opinion

I would think that they would need to be elongated some, but let me get on the rack to verify.

I can offer my own experience with a strut brace mounted on my 986 for 6 years and 80 track days. I did notice a very subtle improvement in chassis stiffness with fewer creaks going over a swale or up my steep curved driveway. It was subjectively a small improvement, not a big improvement but it didn't cost much so...

Did it measurably improve my lap times? No.

Re: a comparison with a front strut brace? A 986 has a very stiff front chassis similar to a 996 GT3 Cup. No front brace is needed there.

Does it work better on an "S" model than a 2.5L? Lateral G forces are the same on both cars in a corner so there would be no difference. Lateral Gs are mostly a result of tire choice and your suspension's ability to control your contact patch.

I expect this to be more of a "feel" than actually improving lap times, the way I look at it I would expect a firmer plant and an improved stiffness over stock. Time will tell.

You get this with the plain bar. Don't get me wrong I like the thought and spec in the product but not sure there is any real benefit in it over and above a plain version.

While this might be true, remember I built this bar for the potential of adjustability at the track, (which could be beneficial on the street as well). I have an appointment at my local spec shop on Friday so I should have numbers soon.

What are you plannimg to adjust on the track? Any attempts to increase negative csmber in this manner would be foolish

I don't know about being "foolish", but we'll see. I would think another degree of negative could be beneficial.

Ok, so the piece that holds your control arms and to which this cross bar attaches is held to the body by two nuts and the front crossbrace.

its a fixed assembly and it bolts flush to the body and sits in locating dowel studs.

You A) want to place this piece, which can crack, under tension.
B) Think that you can push this piece further out enough to create an additional degree of negative camber?

The reality is that this bar's only purpose is to stiffen up the rear of the assembly by joining the aluminum carriers (more so than the aluminum plate) and prevent them from flexing under heavy load.

The rear setup of the 986 can get to about 2.4 degrees of camber even with stock control arms via the eccentric setup. Anyone needing more negative camber than that will likely be running adjustable control arms and/or camber plates.

I applaud anyone trying to make new products for this car, but your claims reflect a serious lack of understanding of how the rear of the car is assembled and the manner in which alignment changes should be made.

So I had a chance to get to the alignment shop today, for two reasons. One I wanted to get my setup to RoW and two to see what adjustability was in this stress bar. What I found was this, my stock setup is good but not perfect, it seems that after 92k miles I may need to get into looking for some worn bushings. But I was able to get the proper camber set for initial lapping.

http://i63.tinypic.com/29y74p.jpg

However, what I did find regarding this bar was that simply turning the bar one turn in or out would adjust the toe angle only, one turn IN would change the angle out .10 degrees and turning the bar OUT would result in a .10 degree change in from stock. So no significant camber adjustments, which is kinda what I expected. However after some "spirited" driving after the alignment, I did notice a stiffer feel to the rear.

Your new alignment specs look good and will maximize your car for stock suspension running dual purpose street/track use, with much better tire wear. It should turn in better and feel more planted in a high speed 3rd gear sweeper. Now to add some tires with more dry grip that hold up well to continuous lapping.

I agree that the lower stress bar is the wrong tool to add negative camber to the rear. The front is where added camber pays the greatest benefits anyways. Fix that first, then evaluate the rear.

The rear stress bar will have to be fully evaluated at the track, but the development of it was mainly to tighten up the rear and solve a potential weak point in that aluminum pan.

Tires may have to wait, just put on a new set of Falkon Ziex 950 to try.

Well, those tires will be fine as an all around commuter A/S tire. On a race track they will overheat and get greasy quick. You will not generate the lateral Gs necessary to thoroughly test your lower stress bar design on those tires.

If you plan to do track days, find a set of takeoff wheels and mount some Extreme performance street tires that add monstrous dry grip and can really take the heat of continuous lapping. They will also make your track day experience more enjoyable.