Shock Adjustment for Idiots: Learn Me

So, my poor FM VMAXX Classics were just not happy with my Miata at the level it is at. At 245whp, with 225 or 245-width 200tw tires, body roll could be best described as "pronounced", even with the huge Racing Beat front sway bar on reinforced mounts.

This is on the 225-width tires, on a cool day, on Seneca Army Depot's notoriously slick surface. Lots of roll, inner front tire almost coming off the ground. Also, struggle with the rear tire coming off the ground, which is no bueno with a Torsen and decent power on tap.

So I took the plunge and ordered the Xida "Race" coilovers from SuperMiata. Chatted with them on what spring rates to run and they said 800lbs in the front and 500lbs in the rear, essentially double what my current coilovers are.

Mmmmm, shiny. Almost too pretty to hide under a car. Also, note the Hot Wheels fleet on my toolbox. There might be a theme (ND Miata, NA Miata, FB RX7)

Problem: They are single adjustable, don't come with any instructions or guide on tuning, and I am kind of dumb on the subject of chassis tuning. 

So, keep it simple, what does adjusting do? No need to get crazy in-depth, just "If you do X, car will act like Y"

I'm guessing I should probably start with  something like 7 clicks in the front and 4 clicks in the rear. I tend to like my cars to be "tight" bordering on understeer (although not a plowing mess), rather than oversteery. I know, I'm weird. 

My theory is: tightening the front and/or loosening the rear makes the car understeer more, and loosening the front and/or tightening the rear makes the rear oversteer more. Am I right, or backwards? Also, seeing as how I'll likely have less body roll, should I back down the negative camber (I'm at -3.5 in front and -2.5 degrees rear) because the suspension will be traveling less?

See if this helps. 

I recommend you start with them full soft and start increasing the damping until you feel the car come into focus. It's easier to feel an underdamped spring than an overdamped one, and I don't like to overdamp the shocks even if it does feel sporty.

Get your fundamental handling balance sorted out with springs, alignment and sway bars. Use a sweeper or a large skidpad for this, you want to isolate transient effects.

THEN you can start tweaking the shocks for transient handling behavior. Keep in mind that this is all shocks do, they only have an effect in transitions. Steady state handling balance, they are not part of the system. Think of them as temporary springs. Play with them a lot, the more you get it wrong the more you'll learn and it's really easy to go back to a previous setting. There is absolutely no substitute for actual experimentation with suspension.

I'm surprised the SuperMiata guys didn't give you at least ballpark starting points.

Keith Tanner said:

I'm surprised the SuperMiata guys didn't give you at least ballpark starting points.

There's a lot of boxes inside boxes, with more boxes and bubble wrap and stickers and invoices, maybe I overlooked them or they are hidden, but I didn't see any. Might have to check again. If they didn't, I'm sure if I e-mailed them, they would tell me where to start.

I also think you should find the acceptable "low and high". What if you run a bumpy course? Might want some softness. Or a nice flat, smooth track May call for the stiffest setting

_ said:

I also think you should find the acceptable "low and high". What if you run a bumpy course? Might want some softness. Or a nice flat, smooth track May call for the stiffest setting

Very good point. Pineview Run is a brand new race track, like 2 years old, and extremely flat and smooth. Meanwhile Seneca Army Depot and Oswego County Airport, where I autocross, are both pretty rough.

info@949racing.com

In reply to NickD :

From a fellow Miata owner, we both know how much it sucks to bump the rear wheels mid corner. 

Stiffer front and softer rear is probably gonna be where your car is happiest.  Then the tuning is just like you said, stiffer in the front will speed up transitioning.  Stiffer in the rear lets the back end rotate more (oversteer).

My autocross setup at this point is full stiff front and full soft rear using MCS coilovers.

When talking to Emilio on the same topic, here was his advice:

There is no idea damping setting for everyone. Not even an ideal setting for a given car on a given track as different drivers will have different preferences. Different weather changes grip which changes ideal shock settings. Every driver needs to invest in a little seat time to do simple 2 or 3 click "sweeps" to see how the car responds. Always start full soft then add the same 2 or 3 clicks at each corner. Drive, make notes (Write Them Down!), adjust, repeat. Adjust past the point where the car feels best just so you can learn to recognize what too much damping feels like. From there, experiment with different front and rear shock settings.

I know in the past, there would be changes I did from summer to winter. Dry to humid. 

I also have Xida's.  I recall Emilio saying at one point that turning the knobs doesn't even start to affect the compression damping until around 12 clicks from full soft (there are around 20 total click IIRC).  As told above, start full soft and start dialing them up until they get too firm.  All other things equal, the most compliant suspension is the fastest suspension (until you start bottoming out).  My experience is that it's much better to have some body roll than it is to have a car that doesn't want to transition its weight until halfway through the turn.

Springs and geometry control body roll, shocks control how fast it rolls.

Looks like you also may have some camber issues, but that will be diminished if the roll is controlled

In reply to ShinnyGroove :

Isn't this also a driving style/technique thing?

The difference between easing it into a corner and tossing it?

It seems to me that a car with high mechanical grip can't be eased into some corners, the slip angle has to be initiated by the turn in or the car won't turn (understeers).

In reply to bentwrench :

I suppose driving style plays a role.  The goal is to get the car's weight settled as quickly as possible after turn-in, you don't want the car's weight shifting around mid turn.

First, you are going to LOVE the Xidas... I also upgraded from VMaxx to Xida 800/500 and the improvement is incredible.

Most of the high points have been hit so far.  I usually start with driving a shock on full soft, then try full hard to feel the range of adjustment.  Then I go back to full soft and start working my way to a setting I like.

KEEP NOTES! - I can't understate the value of keeping notes on settings, feel and times.

In my notes I have a note that 8 clicks from full hard is a good starting point for Hoosiers... not sure where I found that (I don't run Hoosiers, so it wasn't mine).  Might have been the Supermiata site, or one of many threads on MT.net.

My 'middle of the road' setting has been 10 clicks from full hard, and that was determined on NT01s.

Just ran across this older thread. We could, I suppose include a sheet with Xidas that says something like "Start near full soft , drive and experiment by adding 1-2 clicks at all four corners until it feels right". We have found however, that folks that feel they need guidance, will contact us regardless. We have virtually no Xida customers contacting us for advice on how to adjust damping though. In any case, here is something I posted in a FB group the same basic question:

Rules of thumb for any damper: 1. Softer always equals more mechanical grip, so try to run as soft as you can. 2. Stiffer controls excess body movements. Don't be fooled by too stiff settings that feel responsive but reduce overall grip. Just get rid of the wallow. 3. Front and rear will almost always want different settings. 4. What works for one driver, weather condition, tire, may not work for another. 5. Top level drivers may even adjust different left to right to fine tune to a particular track or course. 6. And the big one, there is no "right", "optimum" or "best" setting that anyone trackside can tell you unless they are actually driving the car, and certainly no one on social media that can magically tell you whats right for you. Gotta experiment. Start near full soft and go from there.

HTH

In reply to Emilio700 :

Thanks, Emilio, I appreciate it. I haven't driven it much on the street and the Kung Fu Flu has put racing on hold, but my SCCA chapter is finally going to hold a Test N Tune next Sunday where I'll get to try them out.

They look awesome on the car though and the ride is virtually unchanged from my FM/VMAXX Classics, despite double the spring rate.

I have never quite understood why everyone thinks you should start with damping settings differing front to rear.  In the case of built shocks like Xidas they should already be tuned for the applicable spring rate differential, right? 

Way too many autocrossers are influenced by the workarounds that Stock/Street class requires because you cant change spring rate, so they try to alter handling parameters that are best altered by spring rate change via dampening changes. When they CAN change springs, they rush to the shock settings first, because its what they did on their Stock/Street class car. It becomes common knowledge without knowing for sure why and suddenly its the pervasive tuning knowledge. 

Then again, my last two autocross cars had Konis and I never got to do an extensive tuning session. I seemed to always settle on 1/2 turn off full stiff for autox after doing sweeps at several events on similar surfaces (mildly bumpy asphault). This was on a Mustang and a Miata, both with stiffer than stock spring rates.

Now?  I am running an Fmod.  You can laugh at my lack of dampers, I'm gonna laugh at the cost of your dampers!  Had a fun talk with a buddy running a Formula Ford. He had just finished spending over $2k on rebuilt/revalved/etc dampers and springs.  I bought a $99 sheet of rubber and a $5 hole saw that will let me rebuild my whole cars worth of canisters at least 4-5 times over.  Yeah, shocks would be faster, but at least the direct competition cant have them. That said, adjustments are done via rocker ratios and you need an excel sheet to suss that out. 

In reply to Apexcarver :

Those are very good points that I didn't think of. See, that's why I ask you people these questions

Testing is key, the car may feel better and be easier to drive but be slower. My F500 is this way, it's fastest (for autocross) with a fairly edgy set up.

In reply to NickD :

Did you add the spring rubber ?