Rear Lower Stress Bar Feeler - 986 Forum - The Community for Porsche Boxster & Cayman Owners

mgfranz · 10-20-2018, 04:53 PM

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;

Components;

And installed;

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.

rfuerst911sc · 10-21-2018, 04:43 AM

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

mgfranz · 10-21-2018, 06:16 AM

Quote:

Originally Posted by rfuerst911sc

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.

edc · 10-21-2018, 07:44 AM

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.

mgfranz · 10-21-2018, 08:15 AM

Quote:

Originally Posted by edc

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...

rfuerst911sc · 10-21-2018, 09:46 AM

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 .

mgfranz · 10-21-2018, 01:41 PM

Quote:

Originally Posted by rfuerst911sc

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.

hockenheim · 10-21-2018, 02:40 PM

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?

mgfranz · 10-21-2018, 02:55 PM

Quote:

Originally Posted by hockenheim

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.

Robert986 · 10-22-2018, 11:37 AM

Quote:

Originally Posted by mgfranz

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.

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... ;-)

mgfranz · 10-22-2018, 02:48 PM

Quote:

Originally Posted by Robert986

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... ;-)

Which front brace are you referring to?

rfuerst911sc · 10-23-2018, 12:35 AM

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 .

Topless · 10-23-2018, 08:28 AM

Quote:

Originally Posted by Robert986

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 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.

mgfranz · 10-23-2018, 06:02 PM

Quote:

Originally Posted by Topless

Did it measurably improve my lap times? No.

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.

hockenheim · 10-21-2018, 07:08 PM

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.

maytag · 10-21-2018, 07:40 PM

Quote:

Originally Posted by hockenheim

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.

Sent from my SM-G930T using Tapatalk

mgfranz · 10-21-2018, 08:08 PM

Quote:

Originally Posted by maytag

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

Sent from my SM-G930T using Tapatalk

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

rfuerst911sc · 10-22-2018, 04:46 AM

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

mgfranz · 10-22-2018, 05:09 AM

Quote:

Originally Posted by rfuerst911sc

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

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

mgfranz · 10-21-2018, 07:40 PM

Quote:

Originally Posted by hockenheim

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.

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.