Help me understand suspension tuning with adjustable shocks

The car in question is a 2019 Miata Club RF with Ohlins coilovers, but the question could apply more generally to any car with adjustable shocks.  My suspension is the street/track setup with 7k/4k springs, and the adjustment knob on the shock has about 30 clicks that affect both compression and rebound damping. 

Something I've noticed on forums is that people get these adjustable shock setups and use them as a way to change the car's behavior on the street vs. on the track.  The manufacturers are in on the game too, making different recommendations for street or track use.  For example, on my suspension Ohlins recommends 3-7 clicks from full hard for track use, 7-12 clicks from full hard for canyon carving, and 10-20 clicks for regular street driving.

But this goes against everything I know about how suspensions work.  The general approach I've always understood is as follows:

- choose the tires you want to use

- choose your spring rates to be as compliant as possible for the grip the tires provide while staying off the bump stops

- choose the sway bars to complement the springs and avoid funky stuff that happens with too much body roll (camber curves etc)

- choose the shock damping to match the springs and sways, balancing fast weight transfer vs. oscillation

So here are my questions:

- Isn't there really one ideal critically damped setting for the shocks given the tires, springs and sway bars you're using?

- Wouldn't that ideal damping setting be the same no matter how you're driving the car?

I can see tweaking the damping a little bit to make up for driver preferences.  I can also see it being the 2nd easiest thing to adjust to account for the million little things that aren't linear or perfect on a track car suspension (first easiest being tire pressure).  But cranking up the damping in the shocks for the track just seems like it would make the weight transfer more slowly than necessary on corner entry, and ultimately make the car harder to settle and more unpredictable in transitions.  Am I missing something important here, or is this mostly done by people want their car to feel more "race car" without understanding how suspensions work?

Yes and no. I'd say it depends a lot on what exactly the adjuster is doing. If it's primarily a low speed adjustment, then yes you'd probably want it a bit stiffer for performance driving (assuming relatively smooth road/track) than normal street driving. Low speed damping helps with responsiveness at the expense of awful nvh. But it's also very possible to go too far with that, which is what most oem active damper "sport" modes do. But generally speaking for gross body control there is kind of only one correct setting for the system. You can adjust it a bit to compensate for the springs not really being right, which is where what you referenced about it generally being an easy change to make comes in. Ie for driving to/from the track what you'd really want is softer springs, but it's much easier to dial down the compression a few clicks with kind of the same result.

Well, you'll notice that not ALL shops recommend different street vs track settings :) I suspect a lot of people are trying to use the shocks as temporary springs and like you said, it feels sporty. I generally don't change damping much when going from street to track unless it's to purposefully underdamp on the street to give a slightly more compliant ride. 

For your car, I'd start with the shocks soft and start increasing the damping. You'll feel the car go from underdamped to properly damped. It's a lot easier than feeling the difference between properly damped and overdamped. I'd also switch steps 3 and 4 in your list, the shocks don't really work well to damp sway bars because that varies so much.

To be fair Keith, it was the manufacturer that recommended the different settings in their product literature and not the shop. But regardless, what you guys are saying pretty much supports what I thought- set the shocks to properly dampen the car and leave them there. Thanks

I asked a few people at the track who were adjusting their dampers.  

No kidding here.  “I run full hard for track and full soft for street”  These were Miata, don’t worry I didn’t listen.  Kids, but out there and trying.

My Mustang has nicely matched springs, sway bars and adjustable dampers.  Admittedly I have not experimented much but I will tell you this the rear rides a lot better softened up a bit for street use.  I also soften the front but it doesn’t seem to make as much difference in ride.  A tool box, track gear and a case of water in the trunk will also settle the rear a bit.

The settings that seem rough on the street feel great on the track.  I think the E36 M3ty weight distribution and solid axle will always be a bit of a compromise in one situation or another.   

I had suspension on my E30 for a while with fairly stiff springs but stock sway bars, so plenty of body roll. Shocks were rebound adjustable only, and once I found the setting that didn't oscillate too much over bumps, the only thing I really used them for was to tune body transitions. It made a big difference to have the rears full stiff and the fronts a bit softer to get the car to settle through slaloms. Only discovered this because I like fiddling with things and was just trying stuff, but ultimately it was a bandaid for too little roll stiffness.

The only other time I've felt a need to adjust them regularly is on my Tahoe. High tongue weight = max out the front rebound to prevent nose bob. Changing the rear didn't make enough difference to be worth fiddling with it, which surprised me.

I was messing around with the car tonight so I figured I would play with the damper settings.  I figured out that they are indeed 32 clicks from full hard to full soft; however the last five clicks at the soft end don't adjust anything, you feel the resistance fall off between clicks 27 and 28.  I set them at 25 clicks (almost fully soft) and went for a drive. They didn't feel underdamped at all... impulses like speed bumps or humps in the road were absorbed by the springs, then the chassis immediately returned to it's normal posture without any overshoot or porpoising. As far as I could tell on public roads, cornering was accurate and quick. I guess this isn't too surprising because they use the same shocks for their "race" package which has springs that are like 40% stiffer. I'm going to leave them like this until the weather clears up and I can get it out on the track. 

I was just doing some quick research out of curiosity. The adjusters on these are in fact just bleed adjusters, so low speed adjustment only.

I think the main thing (as with many of these adjustments) is to make a crappy situation better, but not be "correct."

I had a 74 Maverick that I liked to drag race a bit.  It had a 2bbl 302 with ported heads, 10:1 compression, and a pretty hairy cam.  I could get pretty consistent low 12s with a great 950 Holley that I swapped on before staging, but that Holley absolutely sucked on the street.  Undriveable, really.  So I snagged a 2bbl adapter and put the stock 2bbl on it to drive it home and drive it around.  Complete mismatch for the cam and head flow, but it helped the street manners.  It made it bearable.  It started in the cold, didn't have any dead spots, and returned fair mpg... but it was a big mismatch... a mismatch that made it bearable to drive on the street.

I think the point is not that the softer settings are correct, they are just making you not need a chiropractor every time you run over a squirrel.  It's a band-aid.  I think instead of thinking of it as race and street, think of it as race and "not painful to drive for more than 60 seconds."

I think you need to match your damping to the springs, tires, sways, and everything else... to race.  That's the correct setting.  It's just that you can tone it down a bit when not racing and make life less sucky.

Curtis73 (Forum Supporter) said:

I think you need to match your damping to the springs, tires, sways, and everything else... to race.  That's the correct setting.  It's just that you can tone it down a bit when not racing and make life less sucky.

This.  It's similar (but opposite) to the way that Stock class autocrossing used to have cars with really weird damper tuning because you were allowed to change the shocks but not the springs. It's the wrong way to do things, but if it's what you've got available then you do what you can with it.

I owned a 1993 Mustang Cobra R  for a number of years. It came with Koni double adjustable shocks & struts from the factory. Onet of the documents that came with the car was a shock tuning guide from Koni.  That car had very firm springs.  Much stiffer than anything Ford put on the Fox chassis up to that time, well because "race car". What I can remember from the tuning guide was to start out full soft and then adjust the bounce (Compression) rate as firm as you could go while still maintaining grip over bumps. On rebound (Extension) it was similar but if you went to firm the suspension may not recover before hitting another bump resulting in a progressive loss of ride height until you hit the bump stops. At that point bad things handling wise can happen.  

ShinnyGroove (Forum Supporter) said:

I was messing around with the car tonight so I figured I would play with the damper settings.  I figured out that they are indeed 32 clicks from full hard to full soft; however the last five clicks at the soft end don't adjust anything, you feel the resistance fall off between clicks 27 and 28.  I set them at 25 clicks (almost fully soft) and went for a drive. They didn't feel underdamped at all... impulses like speed bumps or humps in the road were absorbed by the springs, then the chassis immediately returned to it's normal posture without any overshoot or porpoising. As far as I could tell on public roads, cornering was accurate and quick. I guess this isn't too surprising because they use the same shocks for their "race" package which has springs that are like 40% stiffer. I'm going to leave them like this until the weather clears up and I can get it out on the track. 

Most shock clickers are just a needle that restricts flow through an orifice, so the impact of one click is usually much more pronounced at the closed end than it is at the open end because the amount you are changing the flow area isn't linear. Not sure if it's considered good practice or not, but I usually go a click or two at a time at the closed end and somewhere around 15-20 clicks out I'll start going 3-5 clicks at a time because otherwise I can't tell if I'm actually feeling something or if it is just in my head because I expect to feel a change.

From the Ohlins users guide, their Dual Flow Valve (DFV) shocks have multiple valves that work in either direction.  The knob adjusts the low speed damping in both directions, and separate non-adjustable valves open in either direction for high speed.

It's hard to describe the resistance when adjusting, but it's basically the same on clicks 1-27 from full hard.  Clicks 28-32 there is no resistance, the knob is just free spinning.  What I take from the above diagrams is that you can have the damping cranked down pretty hard and still not die from going over bumps on the street, because the DFV valves shunt the shock load.  When I bought the car the shocks were cranked down 3 clicks from full hard, and it wasn't terrible.

In reply to ShinnyGroove (Forum Supporter) :

oooh that's pretty cool. Never seen that before! I guess that makes it a digressive damper, and seems a bit like what the dirt bike world does with sprung midvalves on the compression side, but that has a lot more tunability with the secondary blowoff shim stack vs. just using coil spring pressure and works on rebound, too. That's really slick, and seems like it would really let you separate high and low speed damping vs. compromising one to get the other.

The needle in the center of the shaft is what most rebound-adjustable dampers have, and what I was talking about. That is why the rebound adjustment has some impact on both compression and rebound damping - oil flows though both ways unless the nut on the end of the shaft has a check valve in it. The perceived impact is just higher in the rebound direction because flow rates are lower in that direction - the orifice flow chokes and pushes flow through the shim stacks on the piston much more quickly with the higher shaft speeds seen on compression.

At this point pretty much any passenger car damper is digressive to some extent, performance dampers just tend to be a lot more digressive.

That dfv system is a bit of a unique implementation but pretty much every damper manufacturer has some sort of frequency response system which is what that is. To simplify it, basically small but sharp inputs (high frequency) bypass the main valving through the softer secondary valving creating better ride quality, but larger, slower inputs like handling or big bumps still get the stiffer main valving for better body control.

In reply to dps214 :

Right on; my world is revalving and racing dirt bikes which really doesn't have that kind of system unless you get into some of the more unique or high end stuff. You typically get a base valve (comp only, generally low flow rates, has a bleed clicker for LS compression) and a midvalve (rebound and comp with a bleed clicker for LS rebound with some compression crosstalk, looks just like the main piston and clicker setup in that DFV cutaway) in the forks and basically the same thing but with a sprung blowoff on the base valve for the shock. Truly digressive damping is fairly unusual, most of the time linear with slight variation to progressive or digressive gets the best feedback from riders but it's a totally different world than what the suspension has to deal with on a street or track car.

Anyway, enough of me derailing this thread.

In reply to gearheadE30 :

I learned an awful lot about dampers via my motorcycle racing/riding experience.

It's Ohlins; it's automatically excellent.  I put one on my new mountain bike, and instead of reading the manual to figure out how any of the adjustments work, I just rode with the factory settings.  They are generally excellent.

This is from deep in the archives, but it should still help:

Understanding Shock Absorbers, Dampers and Struts | Handling Basics

And here's another one: 

Shock Basics

In reply to ShinnyGroove (Forum Supporter) :

That description says that Ohlins DFV is a blow-off valve like the one used on the Koni FSD shocks. That sort of setup works nicely until you get close to the bumpstops, when a big hit can put you into them pretty hard. I did some A:B testing with FSDs on Mustangs at the SEMA show a few years ago and they were great until they suddenly were not.

rustomatic said:

It's Ohlins; it's automatically excellent.  I put one on my new mountain bike, and instead of reading the manual to figure out how any of the adjustments work, I just rode with the factory settings.  They are generally excellent.

That is a generalization that can get you in trouble. There are some applications where Ohlins has screwed up the math badly in my experience. I can tell you that other shock manufacturers are very jealous of the amount of money Ohlins can charge due to their reputation :)

In reply to Keith Tanner :

I paid half price.  Thirty years on mountain bikes says the E36 M3 works nice, even at full price.  That said, anyone can have a bad day.

You weren't using suspension on mountain bikes 30 years ago :) I sure wasn't. But yeah, brand loyalty is a powerful thing. 

Keith Tanner said:

You weren't using suspension on mountain bikes 30 years ago :) I sure wasn't. But yeah, brand loyalty is a powerful thing. 

Bad memories of the first Rock Shox welling up, thanks.

And Manitous with elastomer springs that worked until a big hit smashed them out against the tube and locked them in, the friction keeping them from extending...

Oh yeah, and the first Trek and GT full suspension bikes that defined biopacing because the swing arm pivot was up higher than the front derailleur.  Good thing they only had like two inches of travel!