• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


Bilstein Science Experiment

OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #41
No there is no coil binding in any of these applications.

I will assemble a OE Ford strut with my ST front spring tomorrow. I can remove the dust boot for proper static measurements. I reckon I can also measure some stock front springs. I think I still have the ones from my car.

My numbers are based on hooking a tape measure on the upper spring perch/bearing and measuring down to the perch. I did that to determine how long to build my damper inserts. The body is borderline too short, but they were some tubes I had left over from another project. I was concerned i wouldn't have enough droop travel, but so far so good.

I measured a stock ST today with 16in wheels and that car from the top of the front whel well to the ground was only about .250ish higher than mine with a driver.

The spring rate of the bumpstops was measured in lbs of force. My spring smasher is a simple linear actuator at the bottom and a load cell at the top. There is a string pot to measure linear travel. I can see the foam "soften" in rate as I pause to make the force measurement.
https://www.ppmracingproducts.com/product/boydbilt-spring-smasher/

If I can get some time tomorrow I will pull the dust boot off the rear damper and see what kind of bump travel I have and put an indicator on the shaft to see how travel works out. I would like to take the rear springs off and put the softer rear springs on the car. Tracking says my front springs should be here Tues, so I will be able to tell you what I have used for bump travel over the last month of street driving.
 


Dialcaliper

Active member
Messages
715
Likes
1,184
Location
San Francisco Bay Area
#43
No there is no coil binding in any of these applications.

I will assemble a OE Ford strut with my ST front spring tomorrow. I can remove the dust boot for proper static measurements. I reckon I can also measure some stock front springs. I think I still have the ones from my car.

My numbers are based on hooking a tape measure on the upper spring perch/bearing and measuring down to the perch. I did that to determine how long to build my damper inserts. The body is borderline too short, but they were some tubes I had left over from another project. I was concerned i wouldn't have enough droop travel, but so far so good.

I measured a stock ST today with 16in wheels and that car from the top of the front whel well to the ground was only about .250ish higher than mine with a driver.

The spring rate of the bumpstops was measured in lbs of force. My spring smasher is a simple linear actuator at the bottom and a load cell at the top. There is a string pot to measure linear travel. I can see the foam "soften" in rate as I pause to make the force measurement.
https://www.ppmracingproducts.com/product/boydbilt-spring-smasher/

If I can get some time tomorrow I will pull the dust boot off the rear damper and see what kind of bump travel I have and put an indicator on the shaft to see how travel works out. I would like to take the rear springs off and put the softer rear springs on the car. Tracking says my front springs should be here Tues, so I will be able to tell you what I have used for bump travel over the last month of street driving.
Alright, since we're doing science here, it's time to take off the gloves and Science the crap out of this. Some of this will be obvious or you've heard it before, some stuff won't be.

The purpose of a car suspension is to handle disturbances in the road. For OEMs, comfort is often the primary concern, with handling a close second. For non-aero performance and racing applications, the primary concern is keeping the rubber in contact with the road to maximize grip. There are other considerations like body roll, controlling weight transfer and turn-in. On racecars with moderate ground effect aero (splitters and diffusers) that produce a car with total net negative lift (not just a wing or lip like most sports cars that provides a little downforce for stability but often still have positive total lift) the concern that overrides optimum mechanical grip especially in the front is maintaining ride height on the track so the downforce is consistent, since this more than makes up for a stiffer than optimum road following or "mechanical grip". (That's all that needs to be said about aero right now)

The "figure of merit" that corresponds to these goals, regardless of car size and corner weight, spring and damper placements ("install ratio" and "motion ratio") is the natural frequency of the spring/mass/damping of the spring, the car body and the shock absorber. It turns out there are some ranges that have been worked out empirically over for as long as there have been automotive dampers for these that work pretty well for any car. This is basically how people who design suspension for both passenger cars and all out race teams decide what a good starting point is, without going into tuning blindly and hoping something works.

Passenger cars: 1.0Hz (comfort)
Sports cars: 1.25-1.75Hz (compromise)
Gravel Rally: 1.5-2.0Hz (max grip on rough surfaces)
Track/Race Cars 2.0-2.5Hz (max grip on "smooth" surfaces, which are not actually smooth)
Aero race cars: 2.5Hz+

We can calculate natural frequency if we know the following:
1) Corner Weight
2) Unsprung Weight
3) Spring Rate
4) Install/ratio (where the spring/strut/shock is mounted relative to the wheel as the length from the control arm pivot to the contact patch of the tire)


If we take corner weight less unsprung weight, we have our "Mass". Spring rate is obvious and our shock/strut is the damper. To get motion ratio (basically how the wheel and body accelerate relative to eachother, we take the install ratio squared apply it to our spring rate to get our effective "wheel rate". Dampers I will go into later once we've picked a spring.

Natural frequency is a simple equation (as long as you convert to kg, newtons and meters)

f = 1/2*pi * sqrt(k/m)

I'll spare you the huge spreadsheet for now on how to actually get there and work out a bunch of other stuff, but there's one thing I should mention

If the front suspension frequency is higher than the rear, the front will recover faster than the rear, which causes the car to "Pitch" forward and back, which is bad because it loads and unloads the axles unevenly and is downright uncomfortable.

If the rear suspension frequency is slightly higher than the front, when you go over a bump/dip, the rear will recover faster tp catch up to the front and the car will "heave" up and down. We want this because it means better control over weight transfer and cornering stability. Also ride comfort. This is referred to as "Flat Ride". Ideally, we want somewhere between 10-30% higher in the rear. Where in that range basically determines the speed range at which the car will be most stable without pitching.

Now, as it turns out, for maximizing mechanical grip, its best to design for near 2.0Hz in the front, and not exceed 2.5 Hz in the rear. This is another empirical number, but it's generally derived from the mass ranges applicable to cars, and the scale of imperfections in a typical asphalt or concrete surface, with the goal of minimizing load variation on the tire.

The stock weight FiST turns out to have frequencies of 1.4F/1.7R for early models and about 1.3F/1.6R for the later models after 2016. Comfortable and a bit sporty. But OEM car manufacturers have a trick these days for sporty car models, which is to increase significantly the shock low rebound closer to or exceeding "critical" damping, which is point where when going over little bumps in the road surface, the restoring force from the spring is not enough to return to center, which tucks up the wheels and makes the car body go down on it's suspension, and on to its modern MCU (multicellular urethane), which being designed to look like christmas trees, possess a very approximately linear spring rate for the first portion of travel. This "spring aid" is used to stiffen the suspension in a corner to improve tire grip. Now my bumpstop calculations might be off, but including these spring aids, frequencies rise to in the range 1.8F/2.2R, for better grip. This is how they maintain ride comfort (on the main spring), and still provide (cheaply) higher performance. Most lowering springs for the FiST are not that much stiffer than the OEM springs, for this reason!

But this approach has drawbacks, specifically the progressive dead-zone of the soft springs, and the excessive high speed rebound damping that results from increasing low-speed damping. Which makes the ride feel stiff and "sporty" which is actually a euphemism for "rides poorly because racecar"

However, if we use something like a Bilstein damper, which as shown by @FusionWorks has less total damping than the OEM, and also more symmetrical compression/rebound, we are no longer jacking down on the stops, and while ride improves, the springs are now not stiff enough on their own and we might want to upgrade.

To get the FiST into the 1.8-2.0Hz range in the front, it turns out we need about 250-350lb/in springs. In the rear, 225-300lb/in will give us a flat ride in the range 2.1-2.4Hz. The Bilstein B14 kit is at the lower end of this range, as are a number of "street" oriented coilovers. Great. Avoid the Ford Racing

Now that we've chosen our springs, we have a different problem, which is that a setup that is optimized for grip might have a bit more body roll than we want (especially with poor geometry struts up front) and also we want to adjust oversteer/understeer behavior. The component we can add that will do this for us, without affecting the main spring rate, is the sway or anti-roll bar. We can then pick out bars that will do that for us, and we can through some different calculations for front and rear roll stiffnesses and lateral load transfer that can get us in the ballpark we want. Not going into that right now though

Now, the purpose of the shock or damper is to a) control the car body from oscillating at its natural frequency every time it goes over a bump, and b) control the unsprung wheel from oscillating and losing contact with the road or transferring too much force to the car body. This is its primary function. Low speed damping controls body oscillation and high speed controls wheel oscillation, We can also dial up the low speed rebound damping a bit if we want smoother transitions, but this feature is often horribly overused and produces a far more terrible ride quality, which if overdone is actually also bad for our grip and keeping the tire in contact with the ground with consistent behavior. Because things go up, and also come back down, what we actually want to do is stiffen our anti-roll bar and possibly increase both rebound and compression together to keep our damping more even.

Another suspension factor that comes from many decades of empirical testing, is that for a typical digressive damper, the (mostly symmetrical) low speed damping that we want is between 50% and 70% times the critical damping rate (basically the slope of the line on the shock dyno), and our high speed damping between 30% and 40% times critical (lower for bumpier roads, higher for smoother tracks). These are basically just high enough to reduce most of the oscillation of the car body and the unsprung wheel where you start getting diminishing returns. Ideally at really high damper speeds, we'd want to reduce damping force to absorb kerbs and rough bumps without transferring as much force to the car body, but that option is usually not available until you get into really high end stuff (Penske/Ohlins), which also have the drawback of needing frequent maintenance and rebuilds to function properly. Lastly, we want to keep up low speed damping long enough to prevent coupling vibration/oscillation between the wheel and car body (instead of between the wheel and ground and the car and ground separately. Bilsteins typically use 3 in/s as the digressive "knee". But general rule of thumb in engineering is that anything above sqrt(2)*natural frequency will avoid couping behavior. If you get really fancy, you can actually calculate both that damper speed, and maximum displacement of our body oscillations since we know our corner mass and wheel rates, and move the knee where we want it, but at least initially, lets work without it.

critical damping = 2*sqrt(mass*wheel rate)

Critical damping rate is defined as the maximum damping of an oscillating system that will still return to This gives us a damping rate in lb/(in/s) or N/(m/s).

For our 350 lb/in front springs above, the critical damping rate comes out to 56 lb per in/s, and for 300 lb/in rear, because of the aft position of the rear damper, critical damping is 26.5 lb per in/s. This means at 3 in/sec (the typical Bilstein knee), anything over 168 lbs of rebound damping force in the front or 80 lbs in the rear will cause the car not return to center on repeated disturbances. These don't even need to be true bumps or "kerbs" any subtle variations in road surface on a smooth track combined with driver inputs that excite oscillation near the natural frequency will cause this behavior, and will heavily jack the car down until it hits the bumpstops which will increasing the spring rate until the system is no longer critically damped. Alternately, compression damping over this value will jack the car up as it goes over the road surface. If both compression and rebound are higher than this, the car will simply be all over the place.

For a 2014-2016 stock main spring (171F/143R), these values are about 39 and 18 lb per in/s, corresponding to 117lb and 54 lb. As you can see from the shock dyno plot that @Fusion Works posted in Post #14 of this thread, the OEM digressive damper (not sure which year) produces about 100lbs compression and 150lbs of rebound at 3 in/sec. This is a classic "jack down" setup, which especially in cornering, will pull the car on to the initial section of its pseudo-linear bumpstops, at which point the spring rate and frequency increase, and the system is no longer critically damped. It produces semi-decent handling, and also produces a terrible (aka "factory sport tuned") ride quality, which sells like hotcakes (because sports-car). For a 2017-2019 car, the critical values are even lower.

For a 250 lb/in front spring, critical damping is 47 lb per in/s, or 141 lb at the knee. If your car is lighter than stock, this value will be a little lower.

Now, as it turns out, anything that goes up must come down, and so to maintain road contact at the ideal natural frequency, we actually want nearly symmetric damping in the 0.5-0.7 range. Here is an example plot from one of many shock tuning guides:

1664179650305.png

There's this persistent myth in the aftermarket that the way to make a car handle well, we need a metric shitton of rebound damping and less compression damping. This is unfortunately one of those things that sticks around. It has its basis in design for much more softly sprung passenger cars and trucks with very soft, often linear compression at 5-20% of critical. To keep such a comfort based setup in contact with the road, you do need an excess in low speed rebound 60-80% critical, or between 3x and 8x times compression damping, just to keep the suspension from being underdamped and oscillating uncontrollably. Obviously more is better right and we should just turn the knob to 11 and keep the same ratios.

It turns out this is not true. As we increase compression damping to improve body control to the levels you want for a performance setup, we actually want to *reduce* rebound damping, or else we will actually reduce grip by increasing load variation on the tires as the car body gets closer to critical damping

Here's a near post that talks about it and a table pulled from a paper it references which is actually referring to over the road trucks, and limit load variation to reduce damage to roads. But it turns out that to optimize grip, we actually want the same sort of thing (consistent tire loads), but with better body control. It is fairly simple to extrapolate the results until you reach the graph and 0.5-0.7 values above.

https://edfishjr.com/2020/12/27/basics-of-shock-tuning-2/
1664180646272.png

So there are basically only a few situations in which you actually want to dial up for high amounts of assymetrical rebound damping nearing or exceeding critical levels.
1) You are tuning an OEM car or truck with comfortable springs and light compression damping
2) You are tuning a "jack down" setup with either progressive springs or MCU bumpstop "spring aids". This is common in autocross and stock classes where you are allowed to change shocks, but are restricted to stock or otherwise limited spring stiffnesses.
3) In autocross, drift, tarmac rally and/or gymkhana setups, where you need to emphasize quick transitions or you don't need to maximize "grip" because you are sliding tires and chassis control is the overriding priority. Sometimes in wheel-to-wheel racing, you might also want to give up a little grip to improve body control as well.

For any street performance, track or racing application, you're better off going for a more stiffly sprung setup to reach the 1.8-2.5Hz range (not exceeding 2.5 Hz), and increasing compression damping along with rebound, but staying below critical damping rates. If you want more body control, add stiffer sway bars to adjust chassis balance. Tuning in little bit of extra damping is okay, but don't go overboard. You'll end up with a setup that gives better traction *and* better ride quality than a heavy rebound biased design.

A jack-down setup with heavy rebound is still a legitimate way to tune a car, especially for autocross, as long as you're aware of the downsides and know that you're doing so intentionally

All that said, these are all just mathematical models of a slightly more complicated system, but we can generally use this as at least a good starting point for further tuning to match driver preferences on how the car should handle.
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #44
I see someone has their Milliken book out and has been studying. LOL

I know Ed, he is one of my customers. Very analytical driver. Did well at Nationals this year, but he is an autoxer.
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #45
I think you over estimate the "jacking down" effect. For a street car shock that won't ever really happen in real life. I have seen dirt track cars with dampers so stiff you can stand on the nose of the car, step off, and the car will stay down for a long enough period you can see it slowly rise back up. This allows the car to be held at an attitude that maximizes angle of attack for the body. I am talking 4-600lbs of zero number with 1500ish lbs of preload on the springs. They have a lot more rebound than most people would believe could work.

In the past, thinking has been the damper is a timing device and you use it to control what the spring is doing. More current thinking is using the shock as a mechanical device and in many cases will be well past critically damped. (we are talking race car not street car here). Street cars have a very wide window of "right" as we have seen from the various tuning examples from the OEs.
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #46
1664200028594.png
Before I built my dampers, this is the calculations I came up with for stock springs. The left side of the column is in/sec the main chart is based on corner weights with 180lb driver, hence the differences left to right.
1664200185765.png

These were my calculations with the 300lb front and 400lb rear springs, I think. Its been a while since I did these so the details in my spreadsheet are thin. Poor notes.
 


Dialcaliper

Active member
Messages
715
Likes
1,184
Location
San Francisco Bay Area
#47
Hey Brett, was wondering if you would be willing to post your after revalve dyno plots? I'm trying to figure out with what I want to go with. I've slowly been cheaping out on my suspension as I've gone through cars. I had Hotbits DT2's on my old Galant VR4. That was gloriously adjustable. The CTS-V got FEALS 441's. Part of the attraction of the FEAL suspension other than they do good work for the price is Odi, had a CTS-V and nerded out and did all the development work in making a great package. Its decently valved for spirited driving and I can tweak it some on track days to extract the balance I want.

I just got some B14's for a song. They are used, but seem be in good condition based on previous owner description of use and driving them. I feel like with the few hundred miles I've put on the setup that I want a tad bit more compression to slow down the g out effect I get on big dips. I feel like the spring rate is about what I would want. I haven't gotten into borrowing my friends scales and going through dynamics calculations. I'm assuming Bilstein spring rates are close to flat ride frequency ratio since I don't notice any pitching issues as far as comfort goes. I'm really trying to avoid nerding out and going head first into suspension (Mechanical Engineer major, and I did lots of work with our schools FSAE car). I already have too many hobbies and a young family that deserves my time.

Once I can iron out what I want from this suspension I'll bring my list of demands to a business in town that just so happens to specialize in Bilstein (https://deltavee.net/). One last concern on the B14's I was thinking about is changing out springs. I feel like having to max out preload to minimize drop to my preferred ride height isn't ideal. So I'd need to source linear springs in a slightly longer size and change spring mounting hardware.

Also completely off topic. Dialcaliper.... I'm assuming you kept your same screen name from the galantvr4.org forum days???
That would also be me. My VR-4 has become a long term ā€œjackstand ballerā€ these days due to life circumstances and a FiST has been recently acquired as a daily driver. Trying (unsuccessfully) not to get *too* carried away modifying itā€¦šŸ¤£

Hoping to get back the Galant and the other project cars eventually
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #48
Bilstein B14 rear spring. Its highly progressive. This is at a normal ride height. I would not use this spring on a track car.


My front strut travel indicator tonight after a month or more of driving with 250lb front springs.




I am probably just barely kissing the bumpstop in a worse case scenario type bump. But so far I am not deep into the Bilstein bumpstop. I will need to pull the bumpstop to measure it, but I think it was about 1.5in. Seeing this travel indicator lets me know I could play with some bump stop packers.

I swapped the 162lb 10in springs for the front tonight and the ST rear lowering springs. Ride is better, still have a bit bouncy, but that is rebound and compression in the dampers. Grip still feels fantastic (limited cool evening drive home) and turn in is immediate as it has always been. (Another feature of the dampers.) Just need to spend more time driving the car to get a better feel for the new spring setup.
 


the duke

Senior Member
Messages
935
Likes
886
Location
Cleveland
#49
That rear spring is appalling. I can visualize the jounce that can create when it unloads and reloads.
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #50
Meh, its just some progressive spring. Pretty sure several companies use something similar on the rear of these cars, just not something I would pick for a performance car. Apparently they ride OK with the stock Bilstein damper curves, but no thanks on anything else.
 


Dialcaliper

Active member
Messages
715
Likes
1,184
Location
San Francisco Bay Area
#51
Good to hear you're getting good results with your dampers, even with slightly softer than OEM spring rates in the front and running a serious front splitter. Suspension tuning has a lot of science, but there's a lot of "black art" to it as well.

The springs that come with the B14 kit are definitely weird - those rear "tender" coils definitely look like they'll close up pretty quickly, but there are not a lot of "active" coils left at the top.

My impression of the kit as delivered was that it was designed as a "performance" upgrade for the base model Fiesta/Mazda 2, and because of that it is less aggressive than the even the stock ST suspension tuning. Its the same with a lot of aftermarket bits, especially chassis parts were designed that way. While there are a few gems out there, many companies were just lazy and relabel their Fiesta parts to fit the ST without bothering to design a better setup than Ford's ST treatment which is actually pretty decent out of the box (with a few glaring OEM design drawbacks). The vast majority of "lowering springs" seem like they are just for appearance and more or less replicate the OEM rates but with worse suspension geometry.
 


Sam4

Senior Member
Messages
833
Likes
653
Location
West Chester, PA, USA
#52
Still trying to pinpoint the etymology of the scientific term "shitton". It seems to be synonymous with "fuckload", but may need a hyphen or even lower-case "e" (tonne). Original usage indicates aquiline-produced carbon footprint...
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#53
Good to hear you're getting good results with your dampers, even with slightly softer than OEM spring rates in the front and running a serious front splitter. Suspension tuning has a lot of science, but there's a lot of "black art" to it as well.

The springs that come with the B14 kit are definitely weird - those rear "tender" coils definitely look like they'll close up pretty quickly, but there are not a lot of "active" coils left at the top.

My impression of the kit as delivered was that it was designed as a "performance" upgrade for the base model Fiesta/Mazda 2, and because of that it is less aggressive than the even the stock ST suspension tuning. Its the same with a lot of aftermarket bits, especially chassis parts were designed that way. While there are a few gems out there, many companies were just lazy and relabel their Fiesta parts to fit the ST without bothering to design a better setup than Ford's ST treatment which is actually pretty decent out of the box (with a few glaring OEM design drawbacks). The vast majority of "lowering springs" seem like they are just for appearance and more or less replicate the OEM rates but with worse suspension geometry.
Some of the springs on the market do increase the rate compared to factory even at their starting progressive rate. The height is the killer part of it all.

The least lowering spring i believe is the Swift at 1" or so which per our discussion is about 0.5" lower than optimal. The rates are slightly higher up front and significantly higher in the rear. 212/212 per their listed rates.
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #54
Yeah, people forget, ignore, or don't realize what happens to a strut suspension when it goes out of its very narrow range of optimal operation. Unlike a dual a-arm car, you can't lower a strut car to much without introducing the need for even heavier spring rates to control the chassis. Most of the lower springs are softer or stock rate and they lower the car. Bad combination for those of use who want maximum performance, not maximum look. I liked the look of the ST springs on my car but knew the ball joint was higher than the inner pivot point. That is all kinda bad for handling.

The Swift seems to be the stiffest "lowering spring". That helps. I wanted to try to use my lowering springs on my new dampers but there really wasn't a good way to accomplish that. I even cut an OE damper open to see if I could stuff a Bilstein insert inside and the ID is just a little on the small side. So no go there. With the off the shelf B6 and B8s struts being crimped twin tube junk, there is no good way to work with the non B14s. If someone has a damaged or used B6 or B8 I would like to cut one open and examine the dimensions inside. It would be nice to see if they could be modified for use with an insert style damper. Then you could use off the shelf lowering springs with a good damper.

I am on day one of driving and its better, but I think the front dampers need a little more bleed as I am getting "short cycling" on the slow shaft speed dips and bumps. Think 20mph or less and just low spots in the pavement or small cracks and such. Feels like the rebound stops the car from making the necessary cycle for "comfort". Will keep driving and see how it feels now.

I'll get a damper curve today.
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#55
Yeah, people forget, ignore, or don't realize what happens to a strut suspension when it goes out of its very narrow range of optimal operation. Unlike a dual a-arm car, you can't lower a strut car to much without introducing the need for even heavier spring rates to control the chassis. Most of the lower springs are softer or stock rate and they lower the car. Bad combination for those of use who want maximum performance, not maximum look. I liked the look of the ST springs on my car but knew the ball joint was higher than the inner pivot point. That is all kinda bad for handling.

The Swift seems to be the stiffest "lowering spring". That helps. I wanted to try to use my lowering springs on my new dampers but there really wasn't a good way to accomplish that. I even cut an OE damper open to see if I could stuff a Bilstein insert inside and the ID is just a little on the small side. So no go there. With the off the shelf B6 and B8s struts being crimped twin tube junk, there is no good way to work with the non B14s. If someone has a damaged or used B6 or B8 I would like to cut one open and examine the dimensions inside. It would be nice to see if they could be modified for use with an insert style damper. Then you could use off the shelf lowering springs with a good damper.

I am on day one of driving and its better, but I think the front dampers need a little more bleed as I am getting "short cycling" on the slow shaft speed dips and bumps. Think 20mph or less and just low spots in the pavement or small cracks and such. Feels like the rebound stops the car from making the necessary cycle for "comfort". Will keep driving and see how it feels now.

I'll get a damper curve today.
PM me an address. Ill send my B8's to you for "science".
 


M-Sport fan

9000 Post Club
Messages
13,996
Likes
6,697
Location
Princeton, N.J.
#56
Some of the springs on the market do increase the rate compared to factory even at their starting progressive rate. The height is the killer part of it all.

The least lowering spring i believe is the Swift at 1" or so which per our discussion is about 0.5" lower than optimal. The rates are slightly higher up front and significantly higher in the rear. 212/212 per their listed rates.
Yeah, if Swift offered those with only a 0.5" static ride height reduction over factory, they'd already be on my car, preferably with some form of re-valved Bilsteins, a la Brett's setup above.

But in order to sell, they must cater to the 'semi-slammer' aesthetic buyers. [:(]
 


OP
Fusion Works

Fusion Works

Active member
Messages
640
Likes
811
Location
Huntsville, AL, USA
Thread Starter #57
I think I can make a spacer that would work with a regular Swift spring set and just set the reduction in height where you want it. it wouldn't be hard to make a top part into a "spacer".

If Kevin will let me cut his front strut open I will know if there is enough room to put the inserts inside of that housing. I may be able to figure it out from external dimensions.
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#58
I think I can make a spacer that would work with a regular Swift spring set and just set the reduction in height where you want it. it wouldn't be hard to make a top part into a "spacer".

If Kevin will let me cut his front strut open I will know if there is enough room to put the inserts inside of that housing. I may be able to figure it out from external dimensions.
You can do anything you want to them. Yours for franken-science-suspension testing. Ill have them out this week. Got caught up with this storm and work so didnt get to send them out last week.
 


Similar threads

Ford Community Posts



Top