944Fest (aka Dan P)

Since I'm a big fan of visuals, here's a low res pic of my BK in place.



<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Skip

[quote]Originally posted by Water944t:
<strong>I read (glanced at) a thread on Corner Carvers describing the fact that strut braces rated somewhere around fart can mufflers as a performance mod.</strong><hr></blockquote>

Not sure what a "fart can muffler" is (I assume they are available at coffee shops), but the strut brace concept depends largely on the car. I've never seen a competitive 944 without one (where allowed). They were installed on all factory 924/944/968 race cars (937, 944TC, 968TRS). All tube-frame renditions of the 944 box and/or triangulate the front towers together.

CC folks tend to a bit hard on the import poser market - I'd bet they are speaking more on the line of cut springs, strut braces, heavy mirrored wheels and cheapo rubber do nothing to improve track times. It'd be hard to argue the positive feel and actual camber deflection negation provided by the strut brace. Though, simply tying the two towers together is not the ideal way to eliminate chassis flex - for this you need 3-4 rigid points of attachment - however, this is disallowed in all but the highly modified classes of racing (tube-frames et al).

In some cars, it is very necessary to install these (Jetta?) - some even in the rear (Civic?) - some even need these down at the lower side also (E30?)... they can not only suffer from poor suspension, but also suffer frame or component damage when driven hard.

Skip

bet

A strut brace is not in the same league as a coffee can exhaust, performance wise. Ok, well maybe if the only performance you are concerned about is 0-60 time

A strut brace completes the "box" of the front suspension. It connects the top of the front towers much like the sway bar connects the bottom. It significantly (some cars more than others) stiffens the front keeping the front strut towers straight on turn in. The result is quicker turn in.

Ahmet

[quote]Originally posted by Z-man:
<strong>Would a front strut brace help this understeering condition? I've heard conflicting ideas (loosen front end vs. tighten front end to help eliminate understeer). Anyone have any thoughts about this?

Thanks,
-Zoltan.</strong><hr></blockquote>

Z, anything that helps the wheels retain their geometry under load will help the tires stick better. If you stiffen the chasis in the front, that will reduce understeer all other things being equal. If you install stiffer springs, that's increasing 'roll stiffness', keeping everything else the same on a given car, increasing roll stiffness on one end of the car will increase the tendency of that end to step out (understeer in the front, oversteer in the rear).

To combat your problem, a strut tower brace may help, I would personally stiffen the rear suspension first however. The type of LSD transaxle you have can also contribute to the understeering problem depending on how much lock up it has under load.
Ahmet

H Dog

The 968 Turbo RS had a Porsche Motorsport strut brace from the factory.

This part is apparently NLA, but suffice it to say that the FACTORY must have thought it a good idea.

Z-man

After all is said and done, I think that rather than getting a strut brace, I will probably get a thicker rear sway bar instead. The strut brace will not make as much a difference as switching out my 16mm rear sway bar with a 20mm or 22mm one.

Other than a sway bar, I can fine-tune the Koni adjustables up front, and mess with the tire pressures to help with the understeer. My current budget restricts me from doing serious work on the suspension.

I feel my money is better spent on a sway bar than a strut tower brace: better return on investment! (Plus I can stay in B-stock during SCCA autox competition!)

Ahmet: unfortunately, I don't have LSD: wish I did though!

Thanks again for the input guys!
-Z.

RPG951S

Here's the CC link:

<a href="http://corner-carvers.com/forums/showthread.php?s=&threadid=448&perpage=40&pagenumber=2" target="_blank">Do strut tower braces do ANYTHING?</a>

Basic conclusion: Maybe, but not much. Won't hurt anything, but may not do anything either.

&gt;&gt;The 968 Turbo RS had a Porsche Motorsport strut brace from the factory.

True, but the factory still churns out drilled rotors by the bucketfull. And we know all about drilled rotors right? Not to mention that crazy design flaw called a rear engine
Nope... definately no marketing driven design going on here. <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />

Water944t

Thats beautiful man...

Thanks for finding that and linking...

Skip

[quote]Originally posted by RPG951S:
<strong>True, but the factory still churns out drilled rotors by the bucketfull. And we know all about drilled rotors right? Not to mention that crazy design flaw called a rear engine
Nope... definately no marketing driven design going on here. <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> </strong><hr></blockquote>

So the CC folks are still one-up on the entire Porsche (and BMW, and Mercedes, and ...) brake engineering programs? I know of which you speak - and have read the entire lengthy drama as it unfolded on two different boards - nothing conclusive that I could see - no one with the facilities and capacity to accurately and scientifically test such things... in or out of real world use. Porsche, or rather the brake firms that produce brake products for Porsche AG, have such useful devices. The only truism of those discussions to date is the hard fact that drilled (cast-holed) rotors are somewhat of a tradeoff or compromise. I find it very hard to believe that so many people developing race cars for top level competition have been wrong for so many years. Not everyone agrees with the CC consortium - it's best to look outside that small box to make your own conclusions. There are many books on the subjects of braking, metallurgy, and so on... one such book you might find at a large library is "Brake Systems: OEM and Racing Brake Technology".

jason952

I contacted sparco in the past, no dice, the part is NLA for awhile from what they said

Jason

RPG951S

Quite true, the CC guys, while certainly well informed from an amateur (I mean non-professional) standpoint can hardly be considered the de facto gurus of braking technology.

I think the point that they were trying to make, and the one that I'm trying to make is that the based on entirely observational data, the result is still inconclusive, some money-is-no-object dedicated race-car manufactures will use it (it: being drilled-brakes, strut bars, etc..etc.), some will not. What the CC guys are doing is rightly point out some of the more ridiculous claims as totally unfounded.

Similarly, 'just' because so-and-so factory does it, does not automatically make it a worthwhile/beneficial/effective. Even automobile manufactures are not designing vehicles in a 'vacuum', with no regards to outside influences.
Quite honestly, Porsche with 911 is the is the quintessential example of this; in 1998 they sold (quite successfully at that!) a $100K + car that was both rear-engined (the ONLY car that was) and air-cooled (again-the ONLY one). They did NOT do this entirely because it was the 'purest' design. They did this because that's exactly what would sell, it's what their customer wants.
What this means is that the average new 911 owner expects both drilled rotor and a strut bar, they'll get it - regardless of actual benefit.

So, where does that leave us? Short of running a [Danno-style ] double/triple blind experiment with a professional driver at the wheel, you just have to go with what you observe, personally.
Had a strut bar for a while, definately felt different. Did it make me faster? Not that I could tell. Took it out for the same reason most people do (class rules didn't allow it). Any difference? Not that I could tell.
As far as drilled rotors, (not on my Porsche) used them: No percieved braking improvement. Cost more. Cracked. I no longer use them.

Skip

[quote]Originally posted by RPG951S:
<strong>Quite honestly, Porsche with 911 is the is the quintessential example of this; in 1998 they sold (quite successfully at that!) a $100K + car that was both rear-engined (the ONLY car that was) and air-cooled (again-the ONLY one)...</strong><hr></blockquote>

Touché Granted, though - the butt-draggers have come a long way lately. To the fact that the 993 and 996 are considered neutral cars, and are able to be driven by mere mortals. Ironically, the GT2 is touted by Porsche: "Should not be driven by the amateur - target audience should be those with years of rear engine driving experience". [laugh] Isn't that a lawsuit waiting to happen - thinking back to the 930 discussion

PCCB's are the latest and greatest from Porsche (SGL Carbon and Brembo) - and they have holes

944Fest (aka Dan P)

I figure a real good way to test this would be to rig some sort of pushrod between the front stuts, with no bar in place. Give it room to play, like a sleeve setup with wet paint or chalk. Bolt up some hoosiers and go honk on it for a while. Bring it back and look at the markings, see if it flexed and scrubbed the paint or whatever.. You would then know for sure how much the fronts were flexing and if the brace is really an asset. Then, and only then could we put this "strut brace worth" argument to bed.
If the factory put them in their racecars, at the expense of a few lbs of weight, you can bet your **** they felt it needed them.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Skip

Excellent idea!!!

I'll drive - I'm, err, uhh, kinda hard on cars - huh

H Dog

[quote]Similarly, 'just' because so-and-so factory does it, does not automatically make it a worthwhile/beneficial/effective. Even automobile manufactures are not designing vehicles in a'vacuum', with no regards to outside influences.
Quite honestly, Porsche with 911 is the is the quintessential example of this; in 1998 they sold <hr></blockquote>

[quote]If the factory put them in their racecars, at the expense of a few lbs of weight, you can bet
your **** they felt it needed them.<hr></blockquote>

Umm, I think the 968 Turbo RS was a RACE car, while the 911 was a STREET car. Yes, even -- hold your breath -- Porsche makes sacrificies for comfort, etc. with their street cars. But for the race track, NO ONE sacrifices in this way. It is all money/performance/rules constrained. I have seen a few web sites which try to "prove" that strut bars are effective, but my analysis of these arguments is inconclusive -- I don't generally buy into their arguments. But if the factory did it, well that speaks volumes to me.

Actually, I think BMW is the quintessential example of marketing "performance". I used to have a 2nd gen M3, and this wasn't that far removed from what it really was - a 332i. Yes, it had nicer bodywork, and bigger wheels, tires, brakes. But aside from that, it wasn't as hairy as the E30 M3. Today, BMW.Williams F1 cars don't even say "BMW M Power" like in the 80s. Instead, just "BMW Power". The M is for marketing, and lots of people are lining up to spend big bucks for the M name -- which they even put on an SUV. Porsches have far fewer compromises than other manufacturers.

Regarding the drilled brakes, Porsche started using them long ago to save weight, not necessarily to help braking performance per se. This is a major issue in handling, especially these days where you'd upgrade to the 322 mm rotor from the stock 298 mm rotor -- an increase in unsprung mass of over 17%. Add 17" wheels (alloy is heavier than air inside the tires) and you have to find weight reductions everywhere you can.

Regarding installing a front strut brace vs. a rear anti roll bar to dial out understeer, the front strut brace will do NOTHING for this, unless you can prove the US is coming from very small geometry changes. US/OS/NS is a function of F/R weight transfer, and the strut bar will not cause the weight to be redistributed from the outside front tire to the outside rear tire.