Strut Tower Brace....Fact or Fiction?

[Vorshlag-Fair]

Norm has some great input here. I will add a few thoughts to this old, tired, silly subject.

1. That video in the first post was a waste of time. It dealt with an old, sloppy, non-rigid, rear engined Porsche chassis. The type of STB you can make to fit on those is radically different than what you can do on a front engined S197. That P-car chassis had been stitch welded, but it is fundamentally MUCH less rigid than a 21st century design like the 2005-14 Mustang. Old cars are floppy tin cans.

2. A simple bolt-on STB is mostly a "scene points" addition on a rigid chassis like the S197. Nobody, nowhere, at no time, can show a measurable LAP TIME DROP with bolt-on braces on these cars. None of the Kenny Brown / Steeda / BMR / company X bolt on braces can be proven to drop lap times in modern chassis. If they COULD prove that, they WOULD. And you'd see all of the bolt-on ding-dongs on every Mustang race car. These mostly are just lightening your wallet. STEELITUS. Why do they make them? BECAUSE GOOF BALLS CONTINUE TO BUY THEM.

3. There are older Mustang chassis (Fox, SN95, etc) and other pre-2000 era OEM chassis designs that DO benefit from a properly built, rigidly made, well installed STB. Maybe, probably, good for long term reliability. But lap time drops? Again - nobody has any A/B track testing data to prove this. Why not? Because it doesn't.

All that said, the stock STB is pretty light and doesn't hurt - if you aren't chasing ounces. We left it on our 2011 TT3 Mustang, which was a heavy pig that we added ballast to to run at the edge of a power-to-weight NASA TT class.

My 2018 GT didn't come with a STB (one came on the PP and a different version came on GT350). We added the aluminum Ford Performance 2-point STB to be able to mount the MCS remote reservoirs to, but never ended up mounting them there (the hoses wouldn't route that way with the long tube headers it had).

The stock S550 STB looked like it was more extensive than you might think - don't be fooled by a plastic cover.

There is an optional, additional steel "U" brace that bolts to the outer firewall (there is an inner firewall too). This does fit under that plastic cover. We added this to my S550 race car build, #BecauseReasons.

Mostly to mount things to, like remote coils, or the shock reservoirs. Figured... it couldn't hurt. But never fool yourself into thinking a STB will "lower lap times". That's not how this works.

Cheers,

 

[Norm Peterson]

The correct term to describe the engineering advantages on street vehicle is "the placebo effect"

"Placebo" isn't quite the right word for what's really going on here - a placebo effect would be entirely imaginary, like a sugar pill in medical drug testing.

But if you're linking 'placebo' to a belief that actual performance has improved "because a little stiffness was added", then yeah. That would be the usual belief, encouraged by what advertising either states or implies. I'll just say that having an engineering outlook does help you filter the BS out from the real tech.

A more solid-feeling chassis is a matter of real perception - the change in vibration modeshapes is strictly a physical phenomenon. There's no imagination involved as long as you keep the ideas of "solid-feeling" and "improved performance" separate like you should.


Some years ago I spent some time working at a local Chevy dealership. I'm mentioning this because it got me out on the shop floor from time to time, where I once specifically noticed an OE STB fitted to a near-luxury level GM car (Buick or Olds, not sure which any more). You know it wasn't there for performance, or for showing off at car shows, which leaves mainly the 'V' part of NVH.


Norm

 

[kerrynzl]

"Placebo" isn't quite the right word for what's really going on here - a placebo effect would be entirely imaginary, like a sugar pill in medical drug testing.

But if you're linking 'placebo' to a belief that actual performance has improved "because a little stiffness was added", then yeah. That would be the usual belief, encouraged by what advertising either states or implies. I'll just say that having an engineering outlook does help you filter the BS out from the real tech.

A more solid-feeling chassis is a matter of real perception - the change in vibration modeshapes is strictly a physical phenomenon. There's no imagination involved as long as you keep the ideas of "solid-feeling" and "improved performance" separate like you should.


Some years ago I spent some time working at a local Chevy dealership. I'm mentioning this because it got me out on the shop floor from time to time, where I once specifically noticed an OE STB fitted to a near-luxury level GM car (Buick or Olds, not sure which any more). You know it wasn't there for performance, or for showing off at car shows, which leaves mainly the 'V' part of NVH.
Norm

Hahaha! I hooked you [there is 2 relevant words overlooked highlighted below]
I have seen "atom polarizers" and "turbonators" lower lap times with novice drivers

The correct term to describe the engineering advantages on street vehicle is "the placebo effect"

On a race car with very high roll stiffness , the "bullshit bar" will help [especially early Mustangs where you need really stiff springs because of the motion ratio to get a decent wheel rate]
But the real frame torsional stiffness comes from a decent multi-point roll cage

On a street car used for occasional track days, a wheel alignment would compensate for any bending loads
Just set the wheel alignment and tyre pressures with a tyre pyrometer

 

[Norm Peterson]

Hahaha! I hooked you [there is 2 relevant words overlooked highlighted below]
I have seen "atom polarizers" and "turbonators" lower lap times with novice drivers

Trust me, I did not overlook 'street vehicle'. What you'd feel is still real even in normal street driving.

The engineering advantages aren't limited to performance driving; you need to look at what else they do. I'm going to refer you back to that Olds/Buick here, as GM wouldn't have included an STB for hard-driving performance reasons in those cars. Added for a more refined, upscale ride, sure.

On a race car with very high roll stiffness , the "bullshit bar" will help [especially early Mustangs where you need really stiff springs because of the motion ratio to get a decent wheel rate]
But the real frame torsional stiffness comes from a decent multi-point roll cage

Agreed. But now you're getting into doing a full-blown FEM dynamic analysis.

You might be interested in reading this paper, which is basically looking for "soft regions" in a fairly serious cage.

983051.fm (clemson.edu)


Norm

 

[Sky Render]

I have a strut tower brace because it dresses up the engine bay. I've had three different strut tower braces from 3 different vendors. They all made zero difference in steering feel, vibration, anything really, if I'm honest.

It might make a small difference on a convertible in terms of NVH or "solidity" as Norm said. But there are no performance benefits.

 

[DieHarder]

I've seen enough of the back and forth to note promoters and detractors on both sides. For me (2006 S197) I've found all of the mods I've done including upgraded wheels, tires, shocks, springs, sway bars, PB, LCA's, UPA, STB, Poly bushings, additional bracing, etc.... (and $$$ thousands later) has only increased handling (in a positive way, stiffer, more composed) and my confidence with the car. Just today, on a short outing I ended up overdoing it a bit turning left onto an on-ramp and though I didn't mean to I ended up drifting the car a bit until she straightened up nicely with a little less throttle, opposite lock and continued on wards though with a little more respect for local conditions (winter & salt).

When I first bought the car I punched it a bit in a light rain one night and thought I was going to swap ends and thus my search for improved handling began. I'll admit some of what I've done may likely not be necessary but I can definitely tell what I've done has improved the feel and feedback of the car to the point where it's more predicable at the edge and when it does get loose provides a more forgiving recovery.

 

[Flusher]

There needs to be a quantifiable and repeatable means of measuring said devices.

The end user is ultimately interested in lap times, i.e. "How much do you (the manufacturer of the part) guarantee that this part will increase my performance?" That's just not possible.

One such method of evaluating components, such as this, would be anchoring three points of the chassis, at the suspension points, then loading the fourth point while measuring deflection. Finally, it is up to the end user to determine if the compromise between rigidity, weight, and cost justify the use. Does the increase in rigidity outweigh the cost in dollars and weight? OR, this part looks so cool, I can't live without it!

the problem with posting test results like this is: 1) It exposes snake oil with a quickness. 2) Ultimately, you end up with a bunch of copycat products all piggybacking on your data. 3) Testing isn't cheap, reliable, or always yield the desired results. 4) The low hanging fruit have already been picked over. It is extremely difficult to develop a product that has a good profit margin, is easy to manufacture, and produces good performance results. Once you do accomplish such a feat, it is expensive and difficult to protect.

 

[kerrynzl]

There needs to be a quantifiable and repeatable means of measuring said devices.

The end user is ultimately interested in lap times, i.e. "How much do you (the manufacturer of the part) guarantee that this part will increase my performance?" That's just not possible.

One such method of evaluating components, such as this, would be anchoring three points of the chassis, at the suspension points, then loading the fourth point while measuring deflection. Finally, it is up to the end user to determine if the compromise between rigidity, weight, and cost justify the use. Does the increase in rigidity outweigh the cost in dollars and weight? OR, this part looks so cool, I can't live without it!

the problem with posting test results like this is: 1) It exposes snake oil with a quickness. 2) Ultimately, you end up with a bunch of copycat products all piggybacking on your data. 3) Testing isn't cheap, reliable, or always yield the desired results. 4) The low hanging fruit have already been picked over. It is extremely difficult to develop a product that has a good profit margin, is easy to manufacture, and produces good performance results. Once you do accomplish such a feat, it is expensive and difficult to protect.

Personally , I think the bars are bullshit! And there is no reason to add unnecessary weight to a vehicle! But..................
I have had some gains with a strut braces .............By cheating or having a thinner interpretation of the rules [than the rule makers intended]
Many years ago we developed an E30 Beemer where spherical bearings and heim joints were not allowed [class rules] but springs and shocks were free. Strut braces were free etc.
A common method for strut braces was to use a heim joint at each end so it can be preloaded [this was allowed]

When we used lower/ stiffer springs, we also shortened the shocks by machining and threading down the tops if the inserts [so the inserts stuck out the top of the platform]
We simply machined some stepped spacers and bolted the strut brace [heim joints] directly to the shock inserts. [a cheat upper platform] The brace also had a "K" member that clamped to it, and attached to the firewall.
The car was significantly faster than others [in a 1 make class] But one caveat! There were lots of other "tweaks" that also contributed to it's results.

 

[Norm Peterson]

The brace also had a "K" member that clamped to it, and attached to the firewall.

I'm guessing that a 4-point STB was either specifically class-illegal or too far outside established rules interpretations to go unnoticed.


Norm

 

[Norm Peterson]

One such method of evaluating components, such as this, would be anchoring three points of the chassis, at the suspension points, then loading the fourth point while measuring deflection. Finally, it is up to the end user to determine if the compromise between rigidity, weight, and cost justify the use. Does the increase in rigidity outweigh the cost in dollars and weight?

It's a huge (and in my opinion unrealistic) assumption to expect most people to be able to reach such conclusions independently from their own knowledge and understanding.

OR, this part looks so cool, I can't live without it!

I'm afraid that for the vast majority of DIY chassis & suspension modifiers this one aspect outweighs all else.

You have to know how to analyze what's going on before you can make any conclusion that doesn't start out with "it looks like it will _____ " (fill in the blank).

Or avoid making conclusions that swap cause with effect (where the visible effect is what causes the actual cause to happen) <sigh>


Norm

 

[kerrynzl]

I'm guessing that a 4-point STB was either specifically class-illegal or too far outside established rules interpretations to go unnoticed.


Norm

It depended on interpretation.
There was no mention of whether the strut brace needing to be straight, or the number of mounting points.
It did get banned unfortunately , because the heim joints were attached directly to the strut inserts [so they interpreted this as a load bearing suspension joint]

While we were arguing over this, they overlooked [or didn't notice] another perfectly legal and difficult to see modification that gave us a significant handling advantage.

 

[stevbd]

If you take the stock bar off notice how much extra room there is in the bolt holes on the brace, I guess for mfg tolerances? With such a loose fit and so much space for the strut tower to move, it's hard to see how a couple 5/8" nuts torqued to 20 ft lbs or so are going to make any noticeable difference.

 

[Norm Peterson]

If you take the stock bar off notice how much extra room there is in the bolt holes on the brace, I guess for mfg tolerances? With such a loose fit and so much space for the strut tower to move, it's hard to see how a couple 5/8" nuts torqued to 20 ft lbs or so are going to make any noticeable difference.

As garage guy's video shows, tensile or compressive loads in the brace really aren't that high. Meaning that it's not going to take a huge amount of joint friction coming from the bolt clamp loads to hold the ends in place.

If clamp loads couldn't hold the brace still, you would get clunking as the bolts take up the bolt to hole clearances first one way and then the other way as one end or the other of the brace slid across its tower a little. Guaranteed there'd be at least one new thread every week about "STB clunking", and people would be throwing them in the trash out of frustration.


Norm

 

[LarryJM]

Cheap mods to a s197 base. It's $100 worth of STB and $600 worth of Tires and Wheels. Then $1000 worth of Big Brakes all the way around. Topped of with a $200 Boss Sway Bar.