Just in - 40 of our custom strut braces for the Porsche 928.

http://www.928motorsports.com/parts/crossbrace.php

We designed it to "exceed the need" of the engine cross brace / strut brace, and stop the bending and breaking issues with the current braces.

Based on the 0.043" seamed material Porsche used in our stock strut brace and the shape - we know that they will:
Yield at 147.44 pounds of force and
Fail at 224.7 pounds of force.

"Yield" means bending beyond the bar's capacity to recover - the point where it takes a permanent bend in the bar.

"Fail" means the point where it would snap or buckle - changing shape dramatically.

Our bar, on the other hand, is made from extruded (seamless) 0.125" wall 6063 T52 alloy will:
Yield at 1126.8 pounds of force, and
Fail at 1448.7 pounds of force.

.... a 650% increase in resistance to bending.

I have seen some cosmetically pretty but badly designed bars out there. Our 928 strut bars are subjected to BOTH compressive forces (ends being pushed together) and tension forces (ends being pulled a part). Under tension (like an understeering 928 scuffing the inside front tire on the pavement) the coil tower tops are being moved away from each other - and any seam or transition from one material to another in this strut bar may be torn apart.

That is why we designed ours to be seamless - all TIG-welded from all the same alloy - so there is no seam or joint to fail.

Here are some pictures - and thank you for your interest.

 

Very nice!

 

What is the weight difference between yours, stock, and the CF versions?

BTW it looks very nice,

 

Seems like a pretty reasonably priced as well i have to admit.

Although I wouldnt put a square tube to do the job of limiting bending and twisting when a simple round tube by design does the job a whole lot better.

 

Carl:

Nice job (as always). Looks cosmetically nice to me too. That thing is far stronger then the bracket on the fender. Actually, the bracket on the fender is rather flimsy (one of mine bent just supporting part of the motor during some work). Does that matter?

 

Not that I have seen many 928's lately performing at the halftime show on 2 wheels, but other than that, why are we in need of this replacement. This goes against the whole premace of Porsche engineering. Don't get me wrong, this is a piece of artwork you have produced and I like it a lot, but would this be for the race guys? It sounds like you have done some research and found a serious fault that I personally wasn't aware of...or at least haven't seen this on any of my cars.

I can plainly see this is better built. Can you do custom inscriptions across the top????

Thanks in advance for the response Carl!

 

Carl,

Just put that onto my to-do list. Unfortunately long and now one item longer.

Any thoughts to making it with a sideways screw? I see that for 944s and they use it to preload and pull the towers together. This gets a touch more camber.

 

Glen,
Somewhere I read that your shouldn't lift the car with the strut brace removed because you can crack the windshield. Do you think lateral screws could pose the same danger? I don't know and I also don't know about the windshield warning; it could be a myth.

 

Thank you for your kind comments.

Let me try to answer sme of these questions:

Weight - this one weighs 1.25 pounds, the stock one weighs .4 pounds, and I do not know what the CF ones weigh, I would guees they would weigh about the same as stock... the carbon fiber is lighter, the stainless steel ends are heavier.

So - of the 3 this is definately the heaviest. But at 1.25 pounds - perhaps not significant. We felt the strength in the suspension was a higher calling here than weight savings.

I am sorry but half of what you said is not true. A round tube does resist twisting better than a square tube - true. But a square tube resists bending better than a round tube.

That is why - before you start to design a suspension piece - you have to understand what direction the forces are coming from. These bars keep the coil towers from separating during hard cornering and from from closing together during regular straight ahead driving.

By looking at all the bent and failed strut braces we could - they had all failed in the same way. Then we were able to design to meet that load better. We did not find a torsion load (twisting) in this member - so designing to resist twisting was not needed.

We heard from customers with CF units that some had pulled the SS end caps off. This comes from the bonding of the joint between the CF and the Stainless. Bonding to Stainless (without a bolt or a weld) is very difficult.

 

Well, it could happen. I have had the car raised with the bar out at least twice. Still no cracks.

One reason I ask is that the last time I did that I noticed that the shock towers had moved apart maybe 3/8" or more. The bar didn't cover the paint marks like it should. After lowering it and drinving it the towers came back. When loosening those bolts the towers would noticably move inwards.

I wouldn't be worried about pulling the towers in a quarter inch or so. Quick math: that might get about 0.3 degrees on a side. I'd take it!

 

Exactly right, Bill. That's why you do reach a point of diminishing returns - the bar is no longer the weakest link - and the mounting plates on each inner fender are. I have not bent or cracked those yet - nor heard of them bending or cracking under cornering loads (possibly because the cross brace failed first) so we will all have to keep our eye on them. They can be stregthened too if need be.

 

It's very pretty and looks very strong, but if I were going to buy something for that job, I would want something that also tied in the shock towers. A bar with a Y on each end that connected to the bracket between the fenders and the shock towers too. Then we are talking about doing away with flex.

At one time on here or the email list someone was talking about making just such a piece, but I think there was not sufficient interest and the idea faded away. Too bad.

cheers,

 

That demostrates how critical this strut brace is - do not drive a 928 without one.

The problem is that right at this location on the car we have two conflicting purposes - you need a big hole between the front springs within which to install a V8, and this is also the very spot you also wish you could triangulate some braces for your suspension.

Next time you jack up and take off a wheel\tire in the front, look at the structure. You will be able to see that the spring/shock mount will not move very much at the bottom because it is well controlled by two a-arms bolted in turn to major frame sections.

But at the top - there is nothing up there to keep the top of the shock and spring from arcing in toward the center-line of the car or out away from centerline - except for this brace tieing one shock tower to the other.

Because of this, when the shock towers move, they do so in an arc. They move very little at the bottom, much more so at the top.

 

Carl, I'll take one for nothin' else but that it looks beautiful.

 

Maybe not race guys - but certainly for performace drivers.

It is very easy to see if your strut brace is bent or not - a yardstick placed across the top can tell you if it is bent - or remove it and place it on a table.
The bend in the bar (if any) means the bar has already failed - it has been pushed beyond its "modulus of elasticity" and is now weaker than before.

I would say - if you enjoy the GT aspects of your 928, the cruising, smooth riding. touring nature it was intended for.... then you do not need this product.
Porsche engineers designed a bar strong enough for you and that style of driving.

But - many of us are adding Eibachs or Hypercoils, installing Konis and cranking them down. Larger swaybars, poly sway bar bushings. Many threads about wider tires exist too. Any of these - all of these - will exert greater force upon that strut bar.

Ask a dismantler how many strut bars they remove from used 928's that are not bent.

So - in answer to you question... just for race? No. For race I think you will want to suppliment even this bar with a Y-bracket that connects to the actual strut tower bolts (see Joe F post above, that is correct for race). But for performance street driving and autocross events, this will do nicely.