Torsion bar modifications vs sway bar upfits

[opusmonday]

Hi Y'all,

I swear I did search for this, but haven't really run into a direct answer. Also this is my first post.

I know that there are a few sway bar kits available for the Fiesta, but also a few kits available that stiffen up the rear torsion bar/twist beam.

I haven't seen a great degree of direct comparisons for results. I do know that both the users of the sway bars and the users of the torsion bar stiffening rods seem to be pretty happy with their choices, and as such I'm wondering if there is a distinct set of benefits and drawbacks for either choice of modification. OR does it all come down to personal preference?

My general usage profile is tooling around on nice days followed by absolutely manic knife edge driving, usually because of reasons. I've found that the rear end seems Very eager to become unplanted when pushed, or on lift. It's unsettling, and I'd like to resolve that.

My fairly sedate little ST for your time.

 

[Hijinx]

A torsion beam bar simply reinforces the torsion beam. A sway bar will attempt to transfer energy from side to side. Yes, this is in the line of the torsion beams job, but the sway bar will load more at the wheels, while the torsion beam bar loads the center of the beam.

Disclaimer: Anecdotal evidence based loosely on science. YMMV.

 

[opusmonday]

Good intel. I'm just trying to play it live in my head visually, as far as terminal loading on a stiffened T-bar versus a sway bar. The real question is which would adapt more suitably to improving the already decent handling of the ST. It nearly feels like I'm three wheeling it when I really push it, and that just... that really doesn't turn my crank. Ultimately, what is needed is more predictable at-limit performance and a longer progression into rotation instead of this sudden Ohmygodwhat'smybuttdoing.

Suspension is not in my wheelhouse, generally speaking. Thank you for replying, by the way, it's a good start.

 

[Young L]

couple of things Ive read people have said that adding the sway bars to the car kill the handling making it too stiff. People seem to either be using a torsion bar or nothing at all.

 

[opusmonday]

And that's kind of my leaning at this point. Augmentation happens two ways. Reinvent the wheel (sway bars). Make the wheel better (torsion bar modifications). I think I may just run the torsion bar modification (Steeda or TB) and see what comes of it. The only thing that makes me leery of the Steeda is the additional modification to the bar, which would make that mod more or less permanent.

 

[westcoaST]

I've gotten really good results with a Pierce Motorsports 6 point frame stiffener coupled with a srrut mount stiffener. It tends to keep the wheel more planted so that the car does not feel like its lifting the rear wheel. Search for Pierce Motorsports on this forum.

 

[opusmonday]

Definitely already on the list. I've got a very bipolar driving style, and there is no medium. 10/10 or grandma/10. I've three wheeled it a few too many times to be comfortable with the prospect of it happening more.

I've gotten really good results with a Pierce Motorsports 6 point frame stiffener coupled with a srrut mount stiffener. It tends to keep the wheel more planted so that the car does not feel like its lifting the rear wheel. Search for Pierce Motorsports on this forum.

 

[Kip2MyLou]

Damn nice list man. Very organized. I have the 2 pt brace and looking at the torsion bar as well. Other than that the only handling part I'd want or need is the upper strut bar bit I've heard those are more for looks than anything. That's why I was saving it for last.

 

[opusmonday]

Damn nice list man. Very organized. I have the 2 pt brace and looking at the torsion bar as well. Other than that the only handling part I'd want or need is the upper strut bar bit I've heard those are more for looks than anything. That's why I was saving it for last.

Thanks on the list! It's going to be a long process I think. Best to keep the wants organized so I know how broke I'm gonna be.

Re: strut bar

You know, I read a very good article today on the upper bar. If I find it I will post it in reply here. The gist is that on it's own, it's only half the package really.

Think about it this way |______________| <If that's your front setup, the verticals being your strut towers, you know that there will be some contortion on stress that will mildly change suspension geometry, with your towers deforming relative to the chassis sort of like /_____________/ or \______________/ or one assumes like /_____________\ (deflection not to scale).

So, adding that top bar will dampen and eliminate lots of that flex.

BUT, to really stiffen up the front you want to compliment that with a lower brace which may stop a lot of that flex from even making it's way into other areas of the chassis. Stop the energy before it spreads, I suppose.

If had to choose only one, I'd take the lower brace over a tower bar. Ideally I'd take both.

 

[Kip2MyLou]

Thanks on the list! It's going to be a long process I think. Best to keep the wants organized so I know how broke I'm gonna be.

Re: strut bar

You know, I read a very good article today on the upper bar. If I find it I will post it in reply here. The gist is that on it's own, it's only half the package really.

Think about it this way |______________| <If that's your front setup, the verticals being your strut towers, you know that there will be some contortion on stress that will mildly change suspension geometry, with your towers deforming relative to the chassis sort of like /_____________/ or \______________/ or one assumes like /_____________\ (deflection not to scale).

So, adding that top bar will dampen and eliminate lots of that flex.

BUT, to really stiffen up the front you want to compliment that with a lower brace which may stop a lot of that flex from even making it's way into other areas of the chassis. Stop the energy before it spreads, I suppose.

If had to choose only one, I'd take the lower brace over a tower bar. Ideally I'd take both.

That makes sense. I already have the 2pt brace as I was told that's all I'll really need for a daily driver. I'll never track or autocross this car so I really don't need the 4 or the 6 pt. I'll probably get the strut bar just to pair it up with the 2 pt strut and support pierce motors a little more. Ha.

 

[opusmonday]

As good a reason as any. The vendor community for the ST is really grassroots, lots of little guys making cool stuff. It's nice to see and support. I'm looking at prototyping a couple things myself, just for sport. The great thing is that the ST is so easy to work on by design that you can't go wrong and the mods come easy. Ford made it an easy car to service on the basis that service dollars keep the dealerships alive.

I'll be taking the six, and mid, as noted. Probably the tower brace as well. It will never see autocross, or a track of any kind, and most of the time I'll be in the slow lane tooling around, but I want it to be as tight as a drum if I need to drive angry, shake an angry horde of imports on a twisty road, or make sudden corrections.

 

[Hijinx]

As good a reason as any. The vendor community for the ST is really grassroots, lots of little guys making cool stuff. It's nice to see and support. I'm looking at prototyping a couple things myself, just for sport. The great thing is that the ST is so easy to work on by design that you can't go wrong and the mods come easy. Ford made it an easy car to service on the basis that service dollars keep the dealerships alive.

I'll be taking the six, and mid, as noted. Probably the tower brace as well. It will never see autocross, or a track of any kind, and most of the time I'll be in the slow lane tooling around, but I want it to be as tight as a drum if I need to drive angry, shake an angry horde of imports on a twisty road, or make sudden corrections.

I have Pierce's 6-point and mid-brace and TB Performance torsion beam bar. Although I have Koni STR.Ts I will try to answer any question you might have about the set up. Right off the bat, I can tell you that this car is very tight, and responsive. Much closer to being indoor kart than your average go-kart. I don't have racing background knowledge but what I can tell you is that there's an extremely small window (by comparison at OEM) from the moment you begin turning in, feel the weight transfer, and the car settle into the angle. It happens much more quickly. At first I wasn't able to perceive it as it seemed to happen instantly. Other things I can tell you is that the rear end tracks much more consistently with my set up. By comparison, OEM is unsure but willing, at its best. Again, anything else you want to know, ask and I'll try my best to answer.

 

[Kip2MyLou]

I have Pierce's 6-point and mid-brace and TB Performance torsion beam bar. Although I have Koni STR.Ts I will try to answer any question you might have about the set up. Right off the bat, I can tell you that this car is very tight, and responsive. Much closer to being indoor kart than your average go-kart. I don't have racing background knowledge but what I can tell you is that there's an extremely small window (by comparison at OEM) from the moment you begin turning in, feel the weight transfer, and the car settle into the angle. It happens much more quickly. At first I wasn't able to perceive it as it seemed to happen instantly. Other things I can tell you is that the rear end tracks much more consistently with my set up. By comparison, OEM is unsure but willing, at its best. Again, anything else you want to know, ask and I'll try my best to answer.

Sounds good. I'll probably just go torsion bar and upper strut bar. Probably call it quits after that. I don't know if it needs much more for my spirited daily driving.

 

[opusmonday]

Thanks for the great reply!

Generally speaking my ultimate goal is to have the car as intuitive and direct as I can make it out to be, which sounds like something you have worked toward in your own modifications. They say a good horse knows what it's rider wants before the rider knows it, and I think the same principals can be applied with this car. Part of that is of course learning to drive what you've created, but the larger portion of the process is creating something that feels like an extension of one's will. Not a separate entity per se.

What I've found and noted elsewhere with the stock setup is that I find it perfectly passable in the day to day (which is admittedly most of my usage), but when I push it to the edge of my comfort zone it becomes moderately unpredictable, especially on less than well kept blacktop. I'd liken it to something almost like the feeling of falling sideways during rear end rotation. It's unsettling, comes on very quickly, and I'm not keen on it.

I ultimately need to dial that out and give the car higher limits and more progressive and predicable rear end slip at the limit. Suspension is not in my wheelhouse, but I think what I may lean toward now is widening the rear track by about 30 mm in total, and nearly that in the front, getting a better tire, a linear set of springs appropriately rated onto a good set of coilovers, coupled with all the body bracing and solid bushings I can find. Corner weighting if I can find someone to do that locally.

I think I'm going to have to read a book or two on suspension lol

 

[Kip2MyLou]

Thanks for the great reply!

Generally speaking my ultimate goal is to have the car as intuitive and direct as I can make it out to be, which sounds like something you have worked toward in your own modifications. They say a good horse knows what it's rider wants before the rider knows it, and I think the same principals can be applied with this car. Part of that is of course learning to drive what you've created, but the larger portion of the process is creating something that feels like an extension of one's will. Not a separate entity per se.

What I've found and noted elsewhere with the stock setup is that I find it perfectly passable in the day to day (which is admittedly most of my usage), but when I push it to the edge of my comfort zone it becomes moderately unpredictable, especially on less than well kept blacktop. I'd liken it to something almost like the feeling of falling sideways during rear end rotation. It's unsettling, comes on very quickly, and I'm not keen on it.

I ultimately need to dial that out and give the car higher limits and more progressive and predicable rear end slip at the limit. Suspension is not in my wheelhouse, but I think what I may lean toward now is widening the rear track by about 30 mm in total, and nearly that in the front, getting a better tire, a linear set of springs appropriately rated onto a good set of coilovers, coupled with all the body bracing and solid bushings I can find. Corner weighting if I can find someone to do that locally.

I think I'm going to have to read a book or two on suspension lol

Damn you looking into way more than I was. Although I agree with everything you've said.

 

[Hijinx]

Thanks for the great reply!

Generally speaking my ultimate goal is to have the car as intuitive and direct as I can make it out to be, which sounds like something you have worked toward in your own modifications. They say a good horse knows what it's rider wants before the rider knows it, and I think the same principals can be applied with this car. Part of that is of course learning to drive what you've created, but the larger portion of the process is creating something that feels like an extension of one's will. Not a separate entity per se.

What I've found and noted elsewhere with the stock setup is that I find it perfectly passable in the day to day (which is admittedly most of my usage), but when I push it to the edge of my comfort zone it becomes moderately unpredictable, especially on less than well kept blacktop. I'd liken it to something almost like the feeling of falling sideways during rear end rotation. It's unsettling, comes on very quickly, and I'm not keen on it.

I ultimately need to dial that out and give the car higher limits and more progressive and predicable rear end slip at the limit. Suspension is not in my wheelhouse, but I think what I may lean toward now is widening the rear track by about 30 mm in total, and nearly that in the front, getting a better tire, a linear set of springs appropriately rated onto a good set of coilovers, coupled with all the body bracing and solid bushings I can find. Corner weighting if I can find someone to do that locally.

I think I'm going to have to read a book or two on suspension lol

What I realized is that in turns on choppy roads, the car does like to skip/jump/shimmy over the bumps. I didn't like that feeling either. This is due to the over-compression of the stock dampers. With my setup it's been eliminated. However, I would like a bit higher spring rate in the front. I'm thinking of going with Eibach springs, with the least amount of drop possible. I thought of maybe going with the Eibach B-spec, true coilovers with monotube dampers. But the spring rates are way high.

 

[opusmonday]

That seems about right. I was pushing it on a left sweeper coming off an overpass, and hit a negative elevation change where the pavement was not very well kept. The suspension just couldn't keep up and nearly tossed me into the weeds.

I'm wondering offhand if it would be cheaper to just have a set of springs wound locally that have the ideal specifications. I might have to choose a very adjustable robust set of coilover shocks that can be rebuilt and serviced* as a long term investment, and then get the ideal springs to match made up. I'm nearly betting it would be cheaper and more satisfying. There's just so much noise in the signal when it comes to suspension, all of it marketing, and not much of it informed by science.

http://www.quickmeme.com/img/41/41ee32edd525cfb6dd5bb239d201f7be9e4ee09f4978726568474989f5bac68a.jpg

What I realized is that in turns on choppy roads, the car does like to skip/jump/shimmy over the bumps. I didn't like that feeling either. This is due to the over-compression of the stock dampers. With my setup it's been eliminated. However, I would like a bit higher spring rate in the front. I'm thinking of going with Eibach springs, with the least amount of drop possible. I thought of maybe going with the Eibach B-spec, true coilovers with monotube dampers. But the spring rates are way high.

 

[dyn085]

Considering the fact that it appears your complaint is driven more by lift-off oversteer, your main focus should be the rear end. That instability was actually intentionally designed into the platform to make it more fun at lower speeds, but that fun comes at the expense of stability at higher speeds.

Spring rate changes would be one of the most effective ways of countering the weight transfer that causes the problem, but on this particular platform I would actually start with tire pressure adjustment and, more importantly, some shims to add camber into the rear tires because that will be far more effective in turns. Do that and get a good alignment first.

After those two, if the high-speed braking (straight-line) instability still bothers you then I would look into spring rates.

 

[opusmonday]

That's valid. It is the high speed stability that I need. I don't generally try to have fun at low speeds. 10/10 or grandma/10. In the former case, I have a tendency to overcook and lift and I may have to work on my own habituation with that aspect of things as well. As noted above, it's the driver's responsibility to learn how to drive what he has built or bought. I'm still going to have to dial that lift oversteer down a bit, though, or create a more linear breaking point.

Tire pressure and shims are great but in for a penny in for a pound. Might as well completely revitalize the deficiencies in one go. It's only money. Money grows back.

Straight line braking has never been an issue in terms of handling.

With all that said, tell me what you know about spring rates and the like. I get the vibe you've worked with this platform a little more than the average housecat.

Considering the fact that it appears your complaint is driven more by lift-off oversteer, your main focus should be the rear end. That instability was actually intentionally designed into the platform to make it more fun at lower speeds, but that fun comes at the expense of stability at higher speeds.

Spring rate changes would be one of the most effective ways of countering the weight transfer that causes the problem, but on this particular platform I would actually start with tire pressure adjustment and, more importantly, some shims to add camber into the rear tires because that will be far more effective in turns. Do that and get a good alignment first.

After those two, if the high-speed braking (straight-line) instability still bothers you then I would look into spring rates.

 

[TrickSTer]

There are threads here, on books to read on suspension/car setup. I've perused several of them, but am totally fascinated by this one:

http://farnorthracing.com/autocross_secrets.html

Basically, it's saying it's all in the physics, the math; there is a basic way and order to set up any car.

It will make you reconsider your spring/shock/sway bar (or coilover) decisions. (Little things like: the adjustability of shocks is not repeatable, it changes every time you adjust them, like: the importance of matching shocks, matching springs).

I don't know if anyone's done the math on the car in its stock configuration. Then of course it changes as soon as you change the ride height.