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Why do I advocate 'No Knobs Needed'? Adjusting your suspension for various conditions
#1
So if you don't have knobs on your dampers, what can you (or should you) adjust?

In extreme cases of wild temperature changes, you would want to soften damping when the temperatures drop and increase damping when temperatures rise. The shock or hydraulic oil has a natural tendency to decrease viscosity (move more easily) with increased temperature and increase viscosity (more less easily) with lower temperatures. However, if you start with a suspension that utilizes spring rates that create a Flat Ride relationships between the front and rear suspension, the vehicle wants to turn very naturally without 'forcing' it to turn via additional damper force.

When calculating the 'roll damping' needed, it is proportionally lower than the forces required for 'ride damping. This is partially because the vehicle track (the 'lever arm' for roll damping) is usually about 60% of the vehicle wheelbase (the 'lever arm' for ride damping). What this means in plain English is that a transitional 'side-to-side' maneuver (which occurs in the low speed range of the shock's performance curve) needs about 60% of what the vehicle needs to control large amplitude and higher speed range of the shock's performance curve.

I've found in my testing that about 40-45% of critical damping at 1-3 inches / sec is enough to still provide crisp transient control. This is to contrast with a common recommendation of '65-70% of critical damping' that many engineering texts and design course suggest. In practice, this is too much unless you are doing slaloms all day long. 

Once you realize that the majority of yaw control (the vehicle's tendency to rotate) comes from the 1st of the 3 key principles of Ride Harmony - Flat Ride - you can immediately soften up the dampers and enjoy better ride quality plus lower temperature sensitivity (whether cold or hot) of the dampers to environmental changes. The softer damping settings also makes it easier for the suspension to manage dirty / wet / slippery surfaces where you would naturally and sensibly want to soften the damping anyway. Witness any autocross or track event where people run for the shock adjusters to soften their suspensions when it starts to rain! With a well-chosen, supple damping setting (configured at the shop) you only need to adjust tire pressure (usually softer!). 

A few videos to watch that help explain these ideas:














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This is part of an email I sent to a potential FCM Elite customer (they paid for a 30 min consultation already) as we discuss their needs to accommodate street, track, and winter driving conditions. I'm advocating for tuning other variables in the suspension other than the dampers:

So it seems the biggest concern I can address (and via email) is what you would be using the damper adjustments for, when changing from track to summer to winter tires. What would you be changing and why? 

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While you consider what your experience has been, I'll share a bit of mine which I've also gathered since making that video. This is a copy-paste from a comment I made in that video:

"Dennis Grantz from Farnorthracing.com made a strong case for 'tune it on the dyno, not at the racetrack.' Unless you have shock pots and the acquisition equipment to gather useful data (which I've done), it's more dangerous to assume one's butt-dyno is more accurate than years of experience and a solid physical model for how tires develop grip.

The perception of 'stiffer is better' poisons most people into believing when they're just uncomfortable enough their setup is probably as fast as it can get. Too soft? BAD! Too stiff? Well... maybe bad, but GOD FORBID it's TOO SOFT!  So I had to readjust my perceptions to fit actual results, lap times, lateral g data, etc. Then I realized how much marketing BULLSHIT exists on the 'stiffer is better' concept so that is like saying 'the earth is round' when everyone else says "there be dragons!"

So once you swallow this red pill, there's no going back. You'll question every suspension you ride in and consider where it's good or (my experience) deficient. If you really run in wildly different environments then you probably need a tire change as well as a spring rate change. However, given a solid grasp of intended usage, I really believe and have seen myself that the right baseline damping is CRUCIAL. Playing with a low-speed adjuster, or several of them, won't make up for a poor baseline. Whipped cream on a cow pattie is still a cow pattie, but nicer to look at. Especially now with KBO where high-speed compression damping REALLY blows-off like a mofo, our Elite KBO setups have amazing compliance on road surfaces especially because we don't have to overdamp the rebound side, nor worry about too much compression damping build-up."

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Temperature changes are the biggest variable I've found in damper force or any benefit to changing. However, it seems very likely you're not going to be going 10/10ths at the Ring in freezing temperatures. I tune for ~70-80F on our dyno. The damper firms up slightly when cooler and softens slightly when warmer - that's natural response of viscosity to temperature variations. I've run my BMW between freezing winter street conditions and hot track conditions on R-compounds and never felt a need to change the damping. I adjusted ride heights, tire pressures, and my driving style (plus alignment settings if needed), along with adding/subtracting packers. But the damper is really tuned to match the corner weight and the spring rate, NOT the tire. You tune the total roll stiffness, alignment, ride heights to match the tire and grip level provided. For winter driving you need ride height control which a coilover (Bilstein PSS) would give you and that's the basis for your build.

Our ND customer Colin drives his ND Miata in the Chicago area, very cold winter conditions (not usually as much in winter but it experiences wide temperature variations. I have multiple customers who run winter tires and switch to summer tires or track tires in that environment. No one has complained they need more or different damping, especially when other more useful variables are present to make the necessary height or alignment adjustments. Damping is really meant to be dialed in on the dyno and in the workshop, then left alone. That's how F1 tunes and for a good reason. I do a far better job of optimizing a fixed-damping Bilstein than every single 1-way, 2-way, 3-way, or 4-way damper I've ever tested / ridden on. Snippets from two emails Colin sent me are attached, with his feedback.

Part 1 : 'I love the system you created for my miata. If only they came like this from the factory!'

[Image: Colin_ND_feedback1.png]


Part 2: 'The cars been great over the last year, and it's happily hiding from the salt this winter...'

[Image: Colin_ND_feedback2.png]

You are indeed better-off getting KBO than adjustable damping, because of how KBO softens and smooths out the high speed bump response which vastly reduces the upward impact of sharper road features and track kerbing. That's actually why I call it 'Kerb Blow-Off.' You don't *have* to get KBO and still have a highly-optimized damping system (I can get very low high speed slope with my valving methods via Stage 2 tuning) but KBO definitely take the setup to the next level for a discerning track enthusiast as my multiple testimonials have shown. Percy's comments below illustrate how incredible our KBO Stage 3 setup was on his NASA ST2 class E36 M3. It allowed him to soak up the bumps which he couldn't do with an adjustable TC Kline setup.

NASA racer is faster with FCM Elite vs. TC Kline doubles
https://www.youtube.com/watch?v=NWJvJU7vHnM
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#2
Hah! I just posted this thread when I got a reply from the (soon-to-be) new customer -

Quote:“But the damper is really tuned to match the corner weight and the spring rate, NOT the tire. You tune the total roll stiffness, alignment, ride heights to match the tire and grip level provided.” and “Damping is really meant to be dialed in on the dyno and in the workshop, then left alone.”



OK I’m convinced ?

Awesome, I love to see this! Saving money, keeping it simple, and designing an optimized suspension that still has the most important adjustments!
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