Damping and Tire grip?
 

So I've decided to [try to] do things the right way and buy a proper set of coilovers for my NC Miata. Since the NC Xida doesn't exist I'm looking into the FM Fox shocks offering. There just isn't much documentation of user experience with them unfortunately. So I'm looking at the dyno plots.

Emilio from 949 compares the Xidas to the Fox setup here: https://www.miataturbo.net/suspensio...7/#post1258635

he mentions the need for increased compression damping with grippier tires. Can anyone speak to why this is the case? Right now I'm thinking it's a necessity for turn in responsiveness with the increased grip, as well as maybe controlling the weight on a given corner due to increased cornering loads?

You're on the right track. Grippier tires mean well.. you can force more load on a given corner, and faster. More compression damping would probably serve to keep the car more composed over transitions.

Ohlins and FEAL 441s are both also available.


Also: That was NA/NB stuff. NC valving should not be the same. Or at least i'd really hope it's not the same.

Grippier tires will chatter mid-turn without enough compression damping. They will grab, the spring will compress, the car will bounce back due to not enough damping, the tire loses grip then catches again. So it will chatter and skip a bit. There's not enough damping available to contain/moderate the energy imparted to the spring as the grippy tire loads up.

I experienced this for the first time running Toyo RR's on the same settings I had been running RS2's on my gen 1 xidas. Two more clicks damping took care of it.

Did the added grip put you into the bumpstops?
Because being in the bumpstops increases spring rates, which needs more damping. In both bump and rebound.

Me? No. I was not in the bumpstops.

What's your bumpstop length?

I'm not questioning adding 2 clicks fixed this, but your description " the spring will compress, the car will bounce back due to not enough damping, ..." implies not enough rebound damping, not compression.

Point ceded re: my description of events. Single adjustable Xidas adjust rebound & compression together. At least my current ones do; Gen 1 I am not positive. We are in agreement, though, that grippy tires can deliver energy into the spring more quickly, and require more damping for proper control?

One guess is the stronger g-forces load up the rubber suspension bushings more and contributes to the chattering which might need extra damping to handle.
Either that or you're deeper in the bumpstops which increases effective spring rate which need more damping. How long are your bumpstops?

"Grippy tires can deliver energy into the spring more quickly" makes no sense to me.

Ohlins.

I can't spent $2000+ for coilers based on this evidence :)

Without getting bogged down w/ specifics, Emilio's point seemed to be that the Fox setup couldnt hang with a Xida at high tire grip levels. The way I see it is a tire with more grip and response can load the suspension more quickly and with more weight. I am imagining two scenarios; 1: requiring more compression damping ~1in/s for steering response to stay in line with tire capability, 2: mid-corner the damper now has (for example) 1.3x more weight on it than with the less grippy tire. In order for it to properly control that weight and the spring, the damping (maybe both compression and rebound) need to increase.

Ohlins seem nice. Its either Fox, Ohlins, or Tokico/FM springs and I spend the rest on other fun bits.

It blows my mind that this is actually a comparison between Ohlins and Tokicos/Springs or Fox, but then again I also see that you have Megans on an NA.

I don't have first hand evidence to feed to you, going to have to do some searching so you can satisfy yourself on that one.

It's not even really a comparison between those. The comparison quoted was Xidas and Fox..... on an entirely different platform. Not much relevant has actually been posted in here.

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You seem to be an angry, judgy person and I don't want your advice. I don't think you are trying to understand the question I posed, or you wouldn't have responded with "Ohlins" in the first place.

I think you're generalizing what emilio said in that thread and getting confused by taking it out of context. It's not just compression damping needed with more grip- the damping should be determined by other parts of the system which you should decide on first.

You want to choose your spring rates (ultimately the wheel rate/frequencies, determined by springs + sways) to match your tyres / grip level. Then damp that system appropriately, not the other way around as there's no appropriate level of damping for a tire without knowing the wheel frequency/spring rates. Start here: Autocross to Win (DGs Autocross Secrets) - Suspension

Extra load on the spring yes, but there's no extra load on the shock (which is reacts to shaft velocity)

No comparisons have been made or referenced in this thread that are relevant to OP.

I stand by my statement. If this is still confusing, read the OP again. ;)

I guess by "comparison" I meant that the list of options was pretty weird considering the vast differences in performance and cost. Maybe if you switch "comparison" to "consideration" for what I originally said, that's more what I was going for.

They are.

And then the comparison(s) referenced aren't relevant to the consideration in question.

Indeed, sir. I'm wondering, since I cannot have Xidas, whats the next best option? Maybe its Fox, Maybe its not. I'm trying to understand and form a process for evaluating which coilover to select. Thus the initial question came to mind: Why did Emilio say more compression damping was desirable when you step up to better track tires? I may have misinterpreted what Emilio meant (see Junkwhale's comment). The reference to the Tokico setup is that its $1000 less than the higher performing parts, I could then in turn spend that money on something else useful, like cat treats.

Also, my street miata has Megans for two reasons. I was sick of hitting the bump stops w/ factory suspension, and I was sick of reading useless coilover "review" threads in which some one buys a set of coils, installs them, and says now the car feels "more planted". So I found a used set for $400 and tried them out.

Grippier tyres need more everything (spring, damping for the more spring). Emilio's comments re: compression damping were just saying he thought the fox's were underdamped in compression for the springs needed for the amount of grip.

Re: best option, there's no universal best option. Start at the start: what are your goals and what are you going to be doing with the car? Track? Autocross? DD?

I just did my first track day w/ the stock NC and I think I have at least a basic feel for why the Flyin Miata stage 1/2 kits exist and why I wouldn't run it, but the koni sports do look like they could handle a more track oriented spring rate. I'd like to track the car 3-5 times a year and maybe look into some SCCA time trial competition and still remain somewhat comfortable for daily duty ~ 5,000 a year.

Well it boils down to what level of grip tire you want to run in time trial, and how oriented towards that time trial you want your shocks to be. As junkwhale pointed out more succinctly than I tried to, grippier tires need more everything. More spring to keep off the bumpstops. More swaybar to control body roll. More damping, both compression and rebound, to control tire oscillation.

Does MCS make a solution for the NC miata? That would be something to consider.

MCS do 1-way adj, 2-way adj, 2-way adj w/remote reservoir & 3-way adj w/ remote reservoir. Priced $2,850, $3,550, $4,600, $6,100 accordingly. Goodwin & V8R both do Ohlins DFV and can revalve for higher spring rates / higher grip tires. Any of those are going to be on Xida level if set up well (which given what you'll be paying you can expect the shop to help you with specific set-up advice re: spring rates).

Or Feal 441 are a good mid level option ($1400) from Goodwin.

Or even cheaper you could try V8R's $1025 DSD coilovers, they sound like you tbh: https://v8roadsters.com/shop/suspens...-nc-coilovers/

All of these are gonna be way better than Megan Street's on an NA.

haha, the Megans were cheap and better than bouncing off the R-package bumpstops. The NC car will eventually have 215 width tires (like Hankook RS-4s), but I don't plan on getting much more grip than that. So I guess I'll start there. MCS equipment is beyond my budget, but I have been looking at the Feals, also entertaining the idea of some custom bilstein/ground control coilovers.

I haven't tried any of these options and haven't even driven an NC before. But, for the price the DSD coilovers look really good. Full aluminium shocks, good looking dyno charts, backed by V8R - way better option than messing with a bilstein/GC setup imo.

https://v8roadsters.com/wp-content/u...overs-Rear.jpg

I do like the curves, they look consistent through the range. Rear rebound is stronger than front, that's curious. I bet they are a similar insert to Feals, feal just happens to use Swift springs which drive the cost up.