Pick my suspension mods

2017 FiST with 575 miles on it.


Pierce or tb?

Looking at this

http://tbperformanceproducts.com/Pr...-Bar-Trunk-Brace/p/77795963/category=21924899

Or the comparable goodies from pierce. Are front stb's necessary? Looks like the under trunk bar for sure, but not sure what else to do

If you install a Hotchkis or Eibach rear sway bar, I'm not sure there's much benefit in additional bracing; I guess you could install the trunk bar instead, but I think a sway bar would address any handling concerns more directly.

I didn’t notice much difference from the Pierce trunk bar (and Mishimoto’s research showed minimal flexing anyway). It is a well made product though, and I fitted it at the same time as the front upper strut brace, so the effect may be hidden.
I did notice a huge difference with the rear torsion bar and the front traction bar. So they are definitely worth doing. I think the difference between Pierce and TB Performance may be cosmetic, except if you need to clear an aftermarket charge pipe.

Is a rear torsen bar necessary if I end up doing a rear sway bar, or is it redundant?

Traction bar looks solid, I like that too. The trunk brace looked like a lot of people like them but if not much to be had if using a rear sway bar and a traction bar then I'll hard pass

The rear torsion bar is sorta the same thing as a rear sway bar. I would get one or the other.

I got the 6-point Pierce first and holy cow did it transform the car. I enjoyed that for a few months then I wanted more, so I got the Pierce midship brace and the Pierce trunk brace. And again it completely transformed the car. It absolutely points now. The steering is so responsive and instantaneous now that you have to really be smooth with your steering inputs because the slightest movement will move the car. I then added a Pierce rear torsion bar and removed a lot of the body roll. It also helped the car rotate even more, and of course improved turn-in and steering response, albeit at the slight expense of lift-off oversteer.

Anyway, mine is also a '17 and I don't plan on changing the springs or shocks. With just braces and the rear torsion bar the car is transformed and hurts lots of feelings at the track. I've been to 3 track days since I bought the car and after the last one a few weeks ago, I'm not sure there's much left to do suspension wise.

I'm trying to walk a fine line between "too much" and not enough. I drive 100-300 miles a day for work and just not sure how much is too much. I'm leaning with the rear sway bar and front traction bar, amd possibly trunk bar if it had solid gains but it's a coin toss.

No such thing as too much with bracing. It does not affect ride quality at all.

I would do the front torsion bar and the trunk bar if you're worried about "too much." They definitely will have solid gains.

Rear torsion bar and rear sway bay basically have the same effect (stiffening the rear twist beam to reduce body roll). The torsion bar is incredibly easy to fit - 5 min with basic hand tools and a torque wrench.

Front Traction bar (or the 4 or 6 point brace) works well to reduce wheel hop and torque steer, especially in conjunction with an upgraded rear motor mount.

Mountune springs and either stock or Bilstein dampers. Call it done, take the rest of the money and put it towards good tires, lighter wheels, and driver education. I don't believe in a lot of the braces sold on the market. The tires don't produce enough traction to induce enough load into the chassis to cause any flex, and if they did, the braces out there aren't going to do much. The truck brace is the most pointless. The highest forces are transmitted thru the spring perch, which is located on the unibody frame rail and gusseted. The braces attach to the shock tower, which is pure vertical loading. There is no point in tying the shock towers together with a beam that is in tension and compression while the forces are perpendicular. The unibody around the shock tower will provide enough strength to prevent any flex. An upper strut tower brace could have some value since the load path from the springs is at the strut towers and are angled, meaning there is both a vertical and horizontal component. A beam in compression would provide some resistance. However, to produce enough lateral force to flex the strut tower will require some serious tire grip. Until somebody can present some strain values or displacement values indicating those braces do anything other than make your car heavier and wallet lighter, I just don't buy into them. The torsional rigidity of the Fiesta unibody and the load paths of the suspension forces just don't point to these things doing anything. I have worked on some pretty flimsy unibody cars over the past 20 years and the Fiesta isn't one of them.

I would also say no to a rear sway bar. The ST has a stiff twist beam and less negative rear camber to promote oversteer. Change your driving technique to take advantage of the already well developed suspension. If you can't get the ST to rotate, you are driving it wrong. I had problems back with my ZX3 with thinking I needed the biggest rear sway bar, stiffer springs, highly damped shocks, and lots of tire pressure to get it to rotate. Turns out, it was because I wasn't trail braking and would actually brake too late and overwhelm the front tires causing it to understeer. After going to a proper driver school, I can easily get the ST to rotate. In fact, I use Sport mode when autocrossing because it rotates a little too easily by changing how I brake, when I brake, and what foot I use to brake. Don't mask poor driving with parts, it just makes it worse. I did that for years and couldn't figure out the problem. It wasn't the car, it was me. To show how much the driver matters, one of the top 10 fastest autocross cars in our club is my old 2011 Fiesta that I built and sold. With me driving it, the car was at the bottom of the time sheets. With the new owner, it finishes in the top 10 overall out of 100 plus cars. He was many seconds faster than my ST or my friend running a Focus RS. The 2011 Fiesta has a cold air intake, Borla catback, FRPP suspension kit, sticky summer tires, and a short throw shifter. It has about half of the power of my ST, and yet it blows the doors off of it. He doesn't use any braces, a larger rear sway bar, or race tires. Just a good driver with a well put together car.

Have you tried any of the braces on a FiST?

No, I don't see the value. After years of suspension engineering and analyzing forces on metal frames, I just don't see them working well enough on the Fiesta. Plus, for the few autocross events a year that could actually see high enough force generation, the addition of the braces isn't going to make enough of a difference. On my Fox body t-top Mustang, that poor thing needs all the bracing it can get. The unibody is already horribly flimsy, the roof structure has been compromised, the spring rates are 4 times what the factory designed to, I am using far wider and stickier tires than it was designed for, and those cars are known to be terribly weak. I have all sorts of braces and reinforcements welded into key areas. Full length box sectioned sub-frame connectors, strut tower brace (the car also uses adjustable coil-overs, so the strut tower is now part of the spring load path), a 6-point roll bar, rocker panel reinforcement plates, and the unibody is seam welded from the rear bulkhead to the strut tower with as much weld as could be done with car mostly stripped. Even with all of that, it isn't as stiff as it needs to be. Forty year old chassis design and being used well outside the design envelope require additional bracing. The Fiesta is light years ahead in terms of the grade of HSLA used in the construction, the torsional rigidity, and stress members in the car assembly. Without significantly altering the amount of traction, I just don't see being able to input enough force into the chassis to require additional bracing. You just aren't moving far enough outside the designed performance envelope and surely not far enough on the street.

THANK YOU!
Since YOU are an actual former suspension engineer, I will take YOUR (and other MANY time national champions in autocross, like Sam Strano's) word and expertise about this topic over the 'seat of the pants feel' and opinion so many on here go by as PROOF of any difference!

Of course I DO believe, and I think it has been PROVEN, that a FULLY tied-in, triangulated and gusseted, sanctioning body legal 12 point+ roll cage DOES in fact add to unibody rigidity.
But then of course one is adding A LOT of weight, and rendering the car NOT street legal in most states/areas.

Sorry, that's all I needed to read of that post.

I guess I and everyone else must be experiencing placebo effect when we add braces and instantly feel a difference.


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It is only my opinion since I don't have any data to support my hypothesis, but I do bring years of engineering and chassis work to the table. No doubt that a full roll cage increases the strength of the unibody, hence why they are used in competition. You could still make the strut tower brace functional if you tied it to the firewall as well. That would triangulate the brace and reduce flex. Of course, you still need to generate enough cornering force to flex the strut towers. That has always been the issue. How many competition Fiesta's have a strut tower brace? I don't think any of them do. I haven't bothered to study the bracing under the front crossmember to determine if that does anything. The shock tower brace makes the least amount of sense. Companies will still produce the parts because the market things they work and since nobody asks for any actual data (like a dyno for engine parts) on suspension braces, there isn't anything to support the claims.

Since everyone hates somebody who questions internet results, I encourage somebody to post some tech to support the claims. Feeling doesn't count here, it needs to be actual quantifiable data. FEA, strain gage readings, or torsional displacement. Everybody screams for engine dyno results, but nobody asks for proof their suspension modifications do anything. I would be shocked anyone could "feel" micro-inches of differences in strain results with extra bracing. Besides, the bushing displacement is far greater than anything you would have in the chassis. A great deal of the suspension loads are being absorbed inside a rubber bushing, before they can be transmitted to the chassis.

Where is your quantifiable data that says they do NOT work?

Your GT350 is light years ahead of a $13k Fiesta and yet Ford still thought it was necessary to add a front strut tower brace. Odd. Maybe their engineers read too much Internet.

I've done 3 track days with progressively more braces and there is a difference. Sorry that you refuse to believe it. The fact that your Fiesta does better with another driver doesn't prove that braces don't work. It only proves that he's a better driver.

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I don't have any quantifiable data that they don't work, but by looking at the load path and the design of the braces, it is possible to deduce that they aren't going to make a difference that is worth the cost and weight. I am not trying to start a war, but would like to see some data to support the claims. Looking at the design based upon 20+ years of modifying cars, 20 years of mechanical design, 5 years as a suspension engineer, years of mechanical engineering classes, and analyzing countless pictures of race car suspension and chassis design does give me some insight into the topic. I am 100% open to be proven wrong, but all I hear for data is "I feel". How many times do people claim to feel performance from engine parts only to find on the dyno that they aren't correct? There are too many factors that play into the feel versus data, however, even data is highly susceptible to needing perfectly controlled conditions to gather correctly. I have run enough testing over the years to know that is the case. Since asking for data may prove next to impossible without a lab and expensive equipment, I will settle for an explanation on how the shock tower brace could provide any increase in chassis rigidity. Even a vector FBD sketch will do.

As for my Mustang, you are 100% incorrect since you failed to read an earlier post about the car. My Mustang is light years behind the Fiesta in development. It is a 40 year platform borrowed from the Fairmont. Ford spent years adding parts and pieces to those cars in hopes of making them stronger as performance increased. Those cars were underdeveloped in terms of the performance capability that came with later models and surely underdeveloped for competition. The Fiesta on the other hand uses HSLA steel that is strong enough that Ford had to develop new cutting blades for the Jaws of Life cutters. SAE magazine had an entire article talking about how strong the unibody of the Fiesta is and how it was revolutionary to have that level of strength and grade of steel in a small car (this was published back in 2009 when the chassis was new). The Fox Mustang on the other hand has been known to decrease it's wheelbase under road racing conditions because the chassis is so weak that it compresses under braking.

Bottom line, if you want to buy braces and think they work, go right ahead. It isn't my car or my money, so I don't care. I do feel that providing a counterpoint based on my experience is just as valuable to the reader as a post claiming the opposite. The reader can make the choice they want based upon the information provided.

I thought you had a new GT350. I bet you won't find a single owner of the new GT350 that would take off their strut tower brace because they say it doesn't work.

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^^^Yeah, alex thought you had a GT350 because of your username.

On most FULLY to spec caged rally Fiestas, aren't the 'down bars' into the front towers cross braced and triangulated into the firewall with what could appear to be a strut tower bar, or do they only have those 'down bars' with nothing else?

I agree with you that these small, brace manufacturing companies are NOT going to do the expensive, provable/repeatable testing required for a definitive answer, so we may never know.
Also, your claims about the bushings taking up the 'slack/slop' anyway (unless one replaces ALL of them with Heim joints/spherical/'pillow ball' type bushings, which would be unbearable/deafening for rough road street use) makes PERFECT sense.

Nope, just a wee bit out of my price range. I have a 1984 Mustang with the 20th Anniversary GT350 stripes. The BRGT350 username came from my first email account in 1994. Been using ever since. I do agree that you won't find a new GT350 owner that would remove the brace and I do think given the front suspension geometry and the shape of the factory brace, it would function as intended. A little questionable on the Fiesta due to the multiple bends in the shape. Without gusseting, the brace will flex at each bend. Out of all the braces for the Fiesta, the strut tower is the one that may actually work. The reason is that the spring forces are at the strut tower and the towers are angled inward. That has both vertical and horizontal forces. The brace helps with the horizontal component. The best braces are either perfectly straight so they just act in compression or tension or are triangulated back to another structural member of the car.

Yep, you have probably 1/8" of bushing deflection (per bushing) and maybe a few thousands of an inch worth of steel deflection in the chassis. There is also sidewall flexing, wheel flexing, bearing play, and tie rod play that all goes into the system. There are so many pieces moving before the forces are even at the chassis. Now, just as you mentioned, once you start going to polyurethane bushings or Heim joints, the chassis flex becomes more of an issue. Why? Because you are transmitting more load into the chassis. Bushings are springs. Replacing those springs with solid units won't absorb the energy, they just transmit it. When the rest of the system is moving vastly more than the chassis, why invest money into the chassis part? A better solution would be different bushings. Reduce the largest flex member in the equation first.

The competition Fiesta's have a diagonal tube going from the strut tower thru the firewall and into the cage. This way suspension loads are transmitted directly to the skeleton of the car. The rear most cross-car bar at the shock towers is to keep the kicker bars from deflecting in an accident, allow for a good place to secure harnesses, help transmit loads between the sides of the roll cage, and prevent any deformation of a suspension pick-up point in a crash. The shock tower is also a pretty strong part of the car, so it makes sense to place many of the tubes at that location. Many competition cars also use the shock towers to house the rear spring, which now makes it even more important to strengthen. The Fiesta's rear springs are on a perch on the frame, under the floor.