tervesoumi

Thanks for the link to the discussion. That discussion focused on Fox body cars which, I think we can agree are no where near as stiff (stock) as the S197.

Since we are on the S197 section, I can tell you that stock cars driven on street are not going to see the difference like a race set-up. Ford's FR500S as well as every competitor I've seen in Koni/Continental run the STB, I don't think it is for the looks.

908ssp

Do you have pictures? Because every FR500, 302S or 302R I have seen does not have a strut tower bar. They don't even tie the tops of the strut towers to the roll cage which was a normal procedure for race prepped roll bars for years.

Sam Strano

That's the problem. You are assuming the towers are moving dead left and right. They move up and down and in and out. The brace is only held on by the bolts, the load isn't going through the bolts it's going through the tower and the brace itself just ties the two towers together which makes things move less.

157dB

The brace would be useless if the movement was up and down...
Its a friction interface inbetween the brace and upper strut mount bolts.
Cus most braces have SLOTTED mounting holes,
you just simply cannot induce enough pressure with the OEM
upper strut mount bearings bolts to overcome the SLOTTED mounting holes.
The friction coefficient is just not there. Sorry.
The Shelby brace is stamped steel to mate with the upper strut mount sheetmetal.
Thus creating a solid attachment point. Other cheaply made STBs usually
only use 2 bolts per side and STOTTED mounting holes. Useless in my world.
But to each his own. Some cant sheit cash at will and must make decisions
instead of buying any and everything available cus its Cool...

If all this movement was taking place, you would think that there
would be some stress induced cracks in the metal or at least the
paint as an indication of such movement...

Maybe I will glue some glass plates in statigic places and give
it a whirl around the track and see if any of the glass is cracked...

Sam Strano

The towers are angled, they want to move in and up both. Furhter, the tops of the towers are tilted opposite to the way they'd move it. The UMI brace I prefer to sell, and stock braces aren't slotted. The UMI doesn't have to be as it's adjustable for length.

This is a little ridiculous, really. I'm a huge "prove it" kind of person and where the world says that you need say to change LCA's because the stock ones are junk, I tend to disagree that it's a must, but it can help. Here we're talking about parts that the OEM spend good money to put on, and trust me I know first hand how they don't want to spend money where it's not deemed necessary. For instance I know the cost involved in upgrading the MT82 to a higher torque rating, per car... and it was not done due to costs being considered too high.

I don't sell may STB's, because a lot of cars come with them now and folks don't think much of them. But when the S in STB is strut, they do matter. And the stronger the brace the more it matters (not all braces are the same. The OEM brace is much weaker than a UMI for instance). When the S in STB stands for shock, as in a 4th gen F-body that doesn't use a strut but a double a-arm setup with coil-over shock, then I don't think they are worth much at all as the loads in those towers are completely different, and much less than a true strut car.

JCON

My 05 Mustang GT doesn't have one yet but I did just get a GT500 brace in... will check fitment later this week. We did however put one on our project 300ZX TT. It made a very noticeable difference in handling, especially in cornering.

Torsional Rigidity:
Ford Mustang 2005 21,000 Nm/deg
300 ZX Less than 1 mm per 10kN (0.036 in./ton)

Any physics professors or mechanical engineers care to convert those to the same units? (would be easier if I could identify the length used for the 300ZX)

I know the ZX was strong enough that it stood with minimal flexing on three jack stands and the doors, hood, deck lid were still aligned. Adding the two point Carbing strut tower brace kept the care planted in corners and allowed us to push it harder/faster without backing off to stay on the pavement. I don't know what a similar system will do for the Mustang but based on experience I would expect some noticeable handling increase.

Norm Peterson

15,500 ft-lb/deg or 186,000 in-lb/deg


Unfortunately, this is a translational stiffness of something like 57,000 lb/in and is not expressed in terms that can directly get you to a torsional stiffness. If you knew how the car was supported, where the 10kn was applied (as in how far off the car centerline it was applied), and where the deflection of <1mm was measured, then you could put them in the same units as was given for the Mustang.


With respect to strut tower deflection, just tying the two tops together will really only help them to move by the same lateral amount. Now you do get different amounts of lateral force at the two towers because the inside and outside tires develop significantly different forces. That does mean that if they aren't tied together, the tower for the outside wheel can be expected to deflect more than the tower for the inboard wheel. Fine, no problem with that. Not even a problem taking that a step further and concluding that the (more important) outboard wheel would suffer a slightly greater camber loss than the lightly loaded inner tower. Or that tying them together helps the outside tower help you by more than its hurting the inside tower hurts you.

What that-all ignores is the magnitude of these deflections and the resulting compliance camber changes - over about a 20" strut length you're only looking to gain a tenth of a degree or so camber on the outer wheel by tying the towers only to each other - even if the brace is dead straight, fully fixed against slippage at the connections, and not dependent on local bending of the tower metal itself.

Most of the commonly available STBs do not fully meet all of those criteria, and are therefore less than 100% effective at equalizing the tower deflections. Anything with a bend, or an intermediate bolted connection or two, or which does not tie in to the strut mount fasteners themselves is less than 100%. Coming back to that previous 0.1° camber benefit - it might be only 2/3 or half that now.

Yes, it's still a benefit, but its value in terms of performance becomes meaningless everywhere short of the top of whatever competition class you're running in (where you don't leave anything on the table except as limited by rules). On the street, where your camber setting almost certainly isn't within even a whole degree of where best lateral grip is made, making an 0.05° to maybe 0.15° improvement on the outside wheel is meaningless. Even if everything else (tires, inflation, shock settings, etc., etc.) is spot-on perfect. And I didn't even mention the tiny disadvantage of carrying extra weight up high and up front in all of the preceding discussion, which does count very slightly against you. If you are going to count all of the tiny benefits as being in your favor, you also have to keep track of all the tiny disadvantages . . .


Norm

JCON

I came to the conclusion about converting them shortly after pulling a book off the shelf.

The 300ZX had a complete adjustable suspension overhual with the best components available. Then it was tuned by the same shop that finished the complete rebuild of the engine. When they did the suspension, they tuned it for maximum grip for road courses as that's what we original designed the car around. I haven't driven an S197 with a brace yet, probably won't see a huge gain considering everything else is stock. Although for my vert, any stiffness is an added bonus.

Norm Peterson

I'd expect whatever benefit to be of more help to a convertible than a coupe. Or to any less rigid platform than to a more rigid one.


FWIW, I did think I was guessing a bit high with "0.1°". When I later looked through the C-C thread, I found measurements indicating that much less was at stake.

Then I got to thinking a little, and the NVH reduction may indirectly affect the actual overall as-driven performance. It may allow the driver to feel what's going on down at the contact patches a little better (by chasing off a few structural vibration modeshapes) and allow him to on average extract a little more of the ultimate performance. A tenth of a second difference at the Solo Nationals can be the difference of several finishing positions, so you can't downplay this. At least not in that or similar situations (where there are valuable contingencies at stake). But a tenth of a second out of a hundred seconds or so total time driving at the limit is utterly meaningless on the street driving at maybe 40% - 50%.

If you open up the definition of "handling" to include the driver (complete with various strengths, weaknesses, faults, etc.) as well as the car as a mechanical device and the road as that which determines what you have to be able to make the car do - then I suppose you could say that STB's improve handling. As far as that definition is concerned, anyway.

But I'd still characterize any indirect benefit of STBs as being an improvement in how well the driver can actually use the performance that's there, rather than being a mechanical improvement or an improvement in the car's performance potential. And some drivers could be expected to benefit more than others even if driving the very same car in before/after comparison testing.


Norm