I’m motivated to write this blog post as I’m composing an email to a new Elite customer in Australia. My comments to him reminded of me a few builds we did that gave better results than the factory dampers or even a respected aftermarket replacement (always pleasant to hear!). But I wanted to describe WHY I could get these results, what principles i was applying that made a difference compared to companies with much larger R&D budgets and many more ‘official’ engineers than we have at Fat Cat Motorsports (just me, an undercover physicist!).
Rewind the clock to early 2014: I had been sick for a while in early spring with time to do nothing and it got me thinking about ideas behind what a suspension really needed to do, vs. what people thought it ‘should’ do. When I was recovered sufficiently, I made this video I called ‘How to Handle a Raw Egg, Isolate and Control.’
Then, a couple months later in summer, I had been working with customers for some time integrating the idea of high-performance driving with street-compatibility. I’d been contemplating the situation that many people are dealing with: how to make a fun-to-drive suspension that is still soft-enough but not TOO soft? This is the age-old question with tuning performance cars that see significant street driving.
Especially because the vast majority of our Bilstein monotube-based FCM Elite suspensions are not adjustable for damping, it’s very important for me to understand what our customers need their vehicles to do and how to implement it. I sometimes think of myself as the ‘Suspension Whisperer’ because I need to ferret out the subtle behaviors without relying on simply ‘turning a knob.’ With nearly 1,000 unique FCM Elite suspension created since 2004, I have been able to continually refine my understanding and implementation of suspension tuning to get smoother ride, faster lap times, and more grip. So much of this success almost paradoxically comes from having the suspension do less, and treating the entire vehicle is moving as one unified whole instead of separating the ‘front’ and the ‘rear’ which creates a disjointed, harsh, unsettled behavior.
This unified behavior is why ‘Flat Ride’ is such a crucial design choice and fortunately, many factory suspensions these days come with Flat Ride tuning. For those who haven’t seen the video where I discuss the experience with my Audi S4 Avant customer who played with Flat Ride using his airbag suspension(!) even before I began working with him, you can hear me share that story in this video:
Once you have Flat Ride created by the proper choice of front and rear frequencies, you have a vehicle that naturally wants to ‘settle down’ after a bump or dip, because the rear suspension is able to oscillate a little faster to ‘catch up’ with the front. This is a natural phenomenon, like going for a walk with a friend, needing to stop and tie your shoe while your friend keeps going. You need to speed up for a second to catch up to them and your vehicle suspension has to operate in the same way.
Now, all that prefaced, let’s return to the present day, November 2016: This is an email I’m sending to Simon, a new FCM Elite customer in Australia who has a very long commute (40,000 km, or about 24,000 a year!). He’s also a former road-racer who would like to maintain good control but also need more ride comfort than the current suspension allows. Through engaging with him and answering his questions, I realized much of the recent success my Elite customers and I have enjoyed is from actualizing the philosophy of ‘Aggressive Comfort’ and ‘How to Handle a Raw Egg: Isolate and Control.’
As an example, we had a really excellent development project with EricSMG, who drives a BMW E46 M3 couple. The thread where Eric shares his feedback is here and while it’s long, you can search for his username (okay and mine as well!) to jump to the most crucial posts though many other comments are interesting as well:
A summary of Eric’s feedback is here:
and Eric’s introductory post:
Below is my email to Simon:
I’ll address a few point in your consult form that would help optimize your road comfort and also point toward the feel and control you’re looking for:
Simon:”Rear Whiteline adj sway bar set on middle setting. Chassis bracing (front strut bar, rear body brace, + tow bar (best 3 point rear chassis brace you can buy, but heavy!)”
“What is your main ride or handling complaint about your vehicle? If you know what the current suspension brand is, enter here or leave blank.: Car crashes through bumps (jacking down). Nice ride on the freeway until road gets uneven/cracks/joins in concrete freeways are sharp/jarring. Bilstein 3000gT front damper, P11 JDM Bilstein Rear damper.”
SJA: The chassis bracing is definitely an asset to improve ride quality / decouple road impacts from being conducted through the suspension into the passenger compartment. While the dampers are almost certain jacking down, part of the problem with jarring impacts on uneven roads is from sway bar stiffness and the side-to-side coupling behavior intrinsic to their action.
You may want to experiment with softening the Whiteline rear bar another notch and see how the ride quality changes. You can also use a slightly longer / firmer rear bump stop that would provide independent wheel control without coupling the wheels together as the sway bar does. The difference one or two packers make when you’re at the point of a little bump stop contact is quite eye-opening! I used this to good effect on my BMW sedan at Thunderhill raceway, adding a single packer to the right rear suspension to add a little more entry oversteer / slip angle going into Turn 1 (about 90mph entry if you’ve brave enough!). You can also take the packers out if you want to keep ride soft on more broken roads. The idea also of using spring rubbers is worth exploring (just an older reference webpage):
I can obtain them from my bump stop vendor.
SJA: Very reasonable concern. What I’ll share from my experience (with various vehicles and most recently our BMW sedan that I kept OE springs on for nearly a year, playing with various recipes and also tracking the car very hard) is that using firmer low speed compression damping and softer low speed rebound is a key to providing good comfort and also control. You can check out a few posts in this thread about an E46 M3 we tuned Bilstein HDs for where he kept the fairly-soft OE springs for better ride quality:
If you just look for posts by our customer EricSMG that’ll help you see what’s going on. I also posted a compression curve and made a video detailed improvements I found comparing our dampers vs. Bilstein vs. Koni, and even how we can get firmer lower speed compression but also softer high speed compression force vs. Ohlins:
“Suspension is installed! Took me a few hours but everything went easily. Much more compliant / less harsh, and still feels like it’s on rails. I need to set the ride heights and corner balance it next. I’ll pop over to the shop once (I) get it squared away – so you can check it out.”
Great post! It’s great to see fellow hatch backers going with FCM tuning and I’m starting to see my words of wisdom from TTAC + FNW sites being repeated by other FIAT Abarthers on FB groups!
I’m excited to learn about your new piston design especially since I’m starting to save for a KBO build for the front dampers on my Abarth ;).
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