Feisty the "Family Car"

[Dialcaliper]

The Front uses retuned B14 inverted struts, which are essentially a Bilstein motorsport strut. Used Swift 65mm ID springs - 300 lb/in main spring, 3k (168 lb/in) tender, again with a soft spring rubber on the driver's side (which I had to ziptie in as the soft spring rubber seems to want to slip out of the spring). The 65mm ID spring sort of fits on the 62mm Bilstein spring seat, but I decided that like, the rear, it should have an adapter to fit a little more snugly. Got ahold of some old style DNA camber plates (thanks to @kevinatfms) to have a direct fit upper spring seat. Unfortunately DNA has changed the design (possibly twice) since, to one that now requires either the stock plastic upper bearing/seat, or a separate spring seat, which would have meant a 7" spring instead and slightly less available compression travel.

Other than the tuning from FCM, the front was probably the more straightforward of the two shock sets. Shaikh hooked me up with a softer bumpstop, and was also able to remove some of the droop limiter bushings inside to give an additional 30mm of droop, which gives slightly more travel than the stock style strut. Almost every coilover strut available has droop travel reduced by about an inch vs the stock struts, and sometimes reduced compression travel to boot, which is not really a good thing for running the car near stock ride height.

Total shock travel is now around just shy of 4.5" in the front and 6.5" in the rear without pushing into either bumpstop, which while not the level of travel in a proper "rally" coilover, is intended to be plenty enough travel given the 300/224 spring rates such that both bumpstop contact and running out of droop travel will rarely be a problem even on rough backroads.

The setup is tuned to produce 1.9 Hz front and 2.1Hz rear natural frequencies, at the low end of what you'd normally consider a track setup. For a reference point, its stiffer than a Porsche 996 GT3 and a slightly softer than a 996 GT3 RS, neither of which anybody would call "soft"

Despite this, the dampers are producing shockingly good ride quality (far better than stock) in conjunction with the tamed high-speed damping courtesy of FCM's "KBO" (kerb-blowoff) modifications. The gas pressure is also reduced to a level optimized for the damping which helps as well. The best way to describe this setup is probably "tarmac rally", but without the brutal ride typically present in those setups.

There's also another surprise that I'll post on later - a fairly wild experiment I'm trying that you can see in the pictures below. See if you can figure out what it is.

 

[Dialcaliper]

I wish that I had the facilities, tools, and where with all to do a suspension system like this!

It would probably be much more functional for mostly street use than even the 3 way adjustable R2/Rally 4 M-Sport Reigers, for much MUCH less total coin as well.

Honestly, far more functional - You can basically consider these "4-way pre-adjusted" handbuilt dampers that never need to be adjusted again because they are optimized for my spring rates and corner weights. The rebuild process involves dynoing each shock individually, and if necessary, multiple teardown and reassemblies to get them "just right" - in other words, a lot of hours of touch labor.

The best part is because they don't have fiddly internal adjustment parts and are built off of Bilstein's very reliable designs, they don't need the 20k mile/100 track hour rebuilds a Reiger/Ohlins/Penske require, and should hold up for 70-100k miles before they need a rebuild just like an OEM Bilstein.

Full transparency, not including the custom parts I made myself, the final pricetag was roughly $5500 including the B14's (which I bought used) and the 5125's. A little more if you had to buy the B14 set new. Most of that cost is FCM's flat fee. I did go for the top-of-the-line option FCM offers because to me this is an investment in a car that I intend to keep for a long time.

While I chose to do a lot of the design and fabrication myself up front myself, normally Shaikh would handle that part for you as part of a larger discussion (which is part of what you're paying him for), and he can tailor the setup to your specific use case, not just make a copy of mine. Mine is "trackable off-road daily driver". He can also do anything from a comfortable performance street to a full blown aero race car. He's even tuned a few regional rally cars and will if necessary put in the research for any make and model you want.

If you're interested Shaikh will do a free 30 minute consult over the phone (fill out the form on FCM website). Just be aware that these aren't off-the-shelf and the process may take 9-12 months due to the backlog of orders and the labor involved in each one. He's also got a youtube channel with a lot of in-depth videos about suspension

https://fatcatmotorsports.com/
https://www.youtube.com/@SuspensionTruth

 

[M-Sport fan]

Yes, at that price point one is up into (and possibly even beyond in my case, since no fabrication facilities/skillz) the insane co$t$ of a used, but fully rebuilt/revalved/refurbished Reiger R2 setup.

YES, with the advantage of being a 'set it and forget it' optimized, and much MUCH less frequent rebuild suspension system.

(The Reigers would be more like an every 15K-20K mile full rebuild/refresh, even on the street, than a 20K-30K mile full teardown, depending on the condition of the roads on which they are used.)

Is there any possible way to do that setup without the spring rubbers??

 

[Dialcaliper]

Yes, at that price point one is up into (and possibly even beyond in my case, since no fabrication facilities/skillz) the insane co$t$ of a used, but fully rebuilt/revalved/refurbished Reiger R2 setup.

YES, with the advantage of being a 'set it and forget it' optimized, and much MUCH less frequent rebuild suspension system.

(The Reigers would be more like an every 15K-20K mile full rebuild/refresh, even on the street, than a 20K-30K mile full teardown, depending on the condition of the roads on which they are used.)

Is there any possible way to do that setup without the spring rubbers??

As I mentioned, the fabrication, while I’m pretty proud of it, is not totally required. And this was definitely an investment I spent some time saving up for.

The spring rubbers are not “necessary” at all - I’ve chosen to use them to compensate for the corner weights of the car for some tiny extra adjustment in the same way that using adjustable sway bar end links to remove preload isn’t a strictly required either. They also help slightly with the tendency for the driver’s side tire to rub more than the passenger side. Just another tool in the toolbox.

 

[Dialcaliper]

Now for something completely different....

After doing a lot of research, I came to the realization that between the Mk6, Mk7 and Mk8 Fiesta ST (Fiesta in general), the entire suspension system between the three is shockingly similar. There are definitely subtle differences and tweaks through the years - spring rates and sway bars/rear beam axle changed many times, as did damper tuning, but the basic chassis is the same, and the majority of parts bolt up whether it be struts, control arms, rear hubs, sway bars, etc.

About a year ago, I managed to snag some front knuckles that came from a very low miles Mk8 Fiesta ST that came from Ebay UK. From what I can tell, all the steering ratio changes between Base models, ST and various iterations of Fiesta are all accomplished in the knuckle, while the basic "manual" steering rack is the same unit all throughout. (The EPAS unit is in the steering column). Since then I've been on a quest to see if I can implement the slightly quicker steering ratio by grafting the Mk8 hubs onto my car.

In any case, I've finally done it! Albeit with mixed results that leave me a bit torn.

The good:

1) The steering is slightly quicker. Most noticable on turnin, and tight corners, where I rarely if ever have to take hands off the steering wheel, even in tight hairpins that were a slight stretch before.

2) There is less tire scrub on tight corners. Interestingly, from the measurements I've taken, it appears that Ford did not in fact "shorten" the steering arm. Instead, they increased the Ackerman steer, but moving the outer tie-rod end inward toward the steering rack by about 1/4" (6-7mm) which you can see in the picture below. This means the inner tire turns slightly more and the outer tire turns slightly less, and this effect is increased over the Mk7. I suspect it was partly to compensate for reduced wheel offset on the Mk8 platform. Because the strut axis is tilted both inward toward the center of the car, and also rearward to create caster angle, the tie-rod end is positioned slightly closer to the imaginary axis between the lower balljoint and the strut top. About 10% closer in fact, which is where the 12:1 ratio comes in compared to the 13.6:1 ratio of the Mk7

3) Bumpsteer feels like it has been reduced. I haven't truly measured this, but the car pulls a lot less to one side hitting potholes and uneven road features. This could also be partly to do with the new FCM dampers keeping the wheels in contact with the road, so things are a bit unclear in this department.

4) Stock brakes, balljoints, tie-rods and struts bolt right up. Essentially plug-and-play. The brakes in particular are how I finally confirmed that these hubs came from a Mk8 ST and not a base model or some other Fiesta. Base model brakes use calipers that are mounted slightly closer to the hub. There are some small differences in the casting I'll mention more about below, and the dust shields have some extra vent holes.

The bad:

5) Increased Ackerman is not necessarily good. From a "performance" standpoint. For a street car, it is a win. Tight corners work better with less tire scrub and steering is quicker. However, when you get away from low speed maneuvering into high speed driving where tire "slip angle" comes into play, more Ackerman steering results in higher slip angle on the outside tire as the car turns, putting more stress on the outside tire. High tier race cars tend to use lower Ackerman to make the front tires work at more even slip angles, distributing the cornering load better. Taken to the extreme, Formula 1 actually uses "reverse" Ackerman steering, where the inside tire turns less than the outside tire. So "street car good, track/race car bad"

6) Mk8 may have different alignment specs. On my test setup of the B14 struts, I was able to get camber to about -2.75 deg. On the stock setup, the car was almost bang-on the -1.2 deg camber listed in the service manual. Now I'm struggling to get just over -2.0 deg, even with the DNA adjustable top hats maxed out. My guess is that the Mk8 has at least 0.5 deg less negative camber up front which one part of how Ford was able to change the Mk8 back to a 19mm front sway, and add even more stiffness to the rear, while as far as I can tell, using similar or even softer springs than the Mk7 (even with the rear banana "vectoring" springs)

The ugly:

7) Ford seemingly lowered the front roll center on the Mk8. The physical geometry change is that both the balljoint mounting location, and the tie rod end are both elevated by 3/4" (19-20mm) relative to the hub center and axle. This produces the exact opposite effect as adding a roll center adjuster and bumpsteer correction kit would. The control arms and tie rods lift up closer to horizontal. The end effect is that the virtual front roll center drops by over an inch. Lowering the front roll center results in slighly more body roll, as the suspension compresses and promotes understeer at the limit. Initial turnin is good, but transitioning into hard corners causes the car to shift from the nice mild lift-off oversteer I had before into to ploughing understeer. The effect is not quite as bad on the real Mk8, as part of the roll center change is to compensate for the larger diameter 18" wheels and tires, which inherently lift the whole car and thus the roll center about half an inch. On my car, at near stock ride height, the control arms are now near horizontal as they would be with a lowered car.

Installing these as-is on a car that's actually lowered would result in even more understeer. I understand now why y'all with lowered cars can stand running just a rear sway bar while retaining the stock 19mm sway bar on Pre-2016 cars, and yet on my car near stock height, that setup was almost uncontrollably tail happy and I upgraded my front sway bar to a 22mm aftermarket bar to get a setup I liked. Changing roll centers is another tool for tuning understeer/oversteer just like changing sway bars and adjusting tire pressure and alignment. Its not commonly used on production cars as geometry tends to be relatively fixed, but it's actually quite common on Formula cars using double wishbones with adjustable pivots and ride heights where its basically a just a simple adjustment and the effect on alignment is fairly minimal.

Next steps:

After some extended consideration, I think I may have to take the hubs back off and put the stock ones back on and realign the car. It was a cool experiment, but in order to make the hubs actually work, I would need to add front roll center correction. I've seen that the Hardrace units, the only available for our car, have had some durability issues, so It would have to be a custom adapter block. While I could definitely make something, it would be yet another project. In addition, I would have to either find some extended tie-rod ends that fit meant for some other car, or again, yet another custom part. That, or go through the hassle of elevating the steering rack slightly, which has its own problems. On top of all that, I'd either need to run camber bolts in addition to the DNA adjustable hats, or find some hats with additional adjustment (requiring drilling out the strut tower), which complicates things a lot (the front springs currently seat on the top hat itself.

 

[Dialcaliper]

Another catchup - right around the time I installed the front suspension, I also ran my BFG rivals down to the cords… oops

This time, after having a great experience with a pair on the Miata, I’ve opted for a set of Bridgestone RE-71RS in 215/45R16. Since tire rack had $70 off at the time, I decided to spend it on the heat cycling option

So far, they are great tires! Less bone shattering ride, and more grip if you treat them well. The main difference is that the Rivals could turn at huge slip angles and still grip. They begged to be manhandled and chucked into corners. The Bridgestones by comparison peak more quickly and require a bit more finesse to squeeze out the traction.

One other caveat on the RE-71RS learned from the Miata and confirmed on the FiST - they require plenty of negative camber. At -1.5deg or less, they are vague and floaty - Almost decided I hated them. At -2.0, which I’m at currently on the FiST, they start to give some feedback. At -2.5 to -3.0, they finally wake up and give excellent steering feel. Probably going to swap back to the OEM front knuckles and get back my extra camber

On the trip up to the tire shop, I decided it was time to also swap tires on the electric Fiat, for yet another set of Yokohama V701 Fleva. I had one of the new sets of tires delivered to the shop, and mounted the snow tires to carry everything up. If you’ve ever wondered what a Fiesta looks like with TWELVE rubber donuts crammed inside, look no further 🤣

 

[Dialcaliper]

It is with much sadness that I pulled the Mk8 knuckles off last weekend, and reinstalled the OE knuckle. While I was in there, I replaced the torn balljoints with some Mevotech premium joints that have zerk fittings on the bottom. They seem decent quality and hopefully the boots hold up better than the ones Superpro installed on the control arms.

Getting the old joints out was surprisingly painless. Rented a balljoint press from the parts store along with the “4WD” ford/chevy kit that seemed to fit the best. Kept wishing the press was slightly taller, and the diameters weren’t quite perfect (also had to remove the zerk fittings to press the new ones in.)

Getting the new ones in was a royal pain and the first one wouldn’t go in straight no matter what I did. But it turned out that the *most* important step was the same thing that frustrated me doing the rear control arm bushings. What I missed was deburring the hole completely with a small file - once the burr on one side was gone in, both joints went straight in 🤦

I took a page from “Spark Plug Steve” on YouTube and cut 0.080” of shims before putting on the snap ring in hopes that would help back up the press

I was able to dial back in negative to -2.75 deg, and now that the suspension geometry is back to normal, the midcorner “push” understeer is gone. Much bett

Goes to show what a difference changing the front roll center can make - the only major change to the geometry besides the steering was basically the equivalent of lowering the car 3/4 inch up front, which is enough that the front rapidly loses negative camber in a turn.

Sometimes you do an experiment, and it just doesn’t work out how you how you hope. If someone had the inclination, and could fab up some balljoint extensions to fix the roll center and find some longer outer tie-rods ends that would correct the bump steer, it might work combined with some additional camber adjustment.

 

[jivenene]

Dude.... that was a great read. Thanks for informing me of how much I don't know about suspension lol....

And being that uninformed, as I was looking for stock height upgraded suspension, I came across the fortune auto 500 series. If you buy them OTS, you will get 1" drop minimum. However, they will do small customizations, and I am talking to them to have them make a set at stock or above ride height, adjustable down by 30mm or so.

I don't have the tools, knowledge, or time to do so much R&D as you are (super impressive BTW), so I am stuck with an OTS solution. What is your analysis of the FA 500 setup at stock ride height? Their marketing sure is good lol....

 

[Dialcaliper]

Dude.... that was a great read. Thanks for informing me of how much I don't know about suspension lol....

And being that uninformed, as I was looking for stock height upgraded suspension, I came across the fortune auto 500 series. If you buy them OTS, you will get 1" drop minimum. However, they will do small customizations, and I am talking to them to have them make a set at stock or above ride height, adjustable down by 30mm or so.

I don't have the tools, knowledge, or time to do so much R&D as you are (super impressive BTW), so I am stuck with an OTS solution. What is your analysis of the FA 500 setup at stock ride height? Their marketing sure is good lol....

I don’t have direct experience with FA, but I hear they are making decent stuff - seems like their prices have increased since the last I saw, either due to supply chain, or I would hope for quality improvements.

The main pitfall with adjustable coilovers is that they will need servicing if you expect them to perform over the long term. Even the most ruggedly built high quality stuff (Reiger, Penske, etc) requires rebuilt/refurbishment after at most 20k miles if you expect them to perform as advertised on the dyno plots. I don’t see any engineering justification that a lower budget design would have any better service life, and if anything expect them to “drift” away from factory spec over time.

On the “decent budget” coilover end one of the sacrifices of the “modular” designs used to keep cost down is less overall shock travel, which can affect how well the shocks can maintain road contact, especially at more reasonable spring rates.

Some considerations:
- Ask if they can use a longer travel damper body, or if it’s basically just swapping in a longer spring to change the ride height.
- Don’t be tempted to spec crazy stiff spring rates and beware of the default 7k/4k front biased spring rates. More reasonable spring rate combos are 5k/4k (280/224) for a dual duty (street/track) or 4k/4k (224/224) or even 4k/3k (224/168) for a street focused setup.
- Swift just makes better springs that have higher compression travel and maintain spring rate over time. Usually worth the investment if you intend to keep them for a while.
- Low speed damping controls body motion, and high speed stiffness has the biggest effect on ride quality

On spring rates: To match the frequency around 2.0-2.5Hz, which is equivalent to “track” focused setups on really any car, the absolute highest rates I’d consider would be 350/300lb or 336/280 (6k/5k), and even then that’s pretty stiff. Anything higher is only appropriate for a car with very serious aero, or specialty racing setups like wheel-to-wheel, tarmac rally and gymkhana where car control and responsiveness is more important than outright performance. A front biased setup like 7k/4k only belongs on an aero car where controlling front ride height to maximize downforce becomes more important that “mechanical” tire grip (essentially the tire and car body’s ability to road follow and provide stable grip). An F1 car or LeMans hypercar with enough downforce to is about the only car with any business using >2.5-3.0Hz

The “low sounding” rates are because a) the Fiesta is light, and b) Our Strut/Beam geometry has high motion ratios (spring closer to wheel).

For perspective, to produce the same ride frequencies as the 5k/4k (280/224) combo on our car (1.8F/2.1R in Hz), some other vehicles would use these spring “custom” spring rates. As you can see, rates are all over the place depending on suspension design and car weight:
NA Miata: 7k/8k (392/448)
E46 M3: 6k/13k (336/728)
GR86: 5k/7k (280/392)

Which are incidentally similar to frequencies for many “track pack” options on various sports cars, none of which are “soft”

Factory option cars around 2.0Hz I was able to find numbers and spring rates for:
Porsche 996 GT3 1.8F/2.0R (199/371)
Camaro ZL1 w/1LE (450/1100)
Corvette C8 w/Z07 (826/517)

Most “Street” oriented sports cars target around 1.5-1.7Hz. Examples:
GR86: 1.5Hz (168/224)
996 Turbo: 1.7/1.9Hz (188/342)