Understanding higher spring rates
 

The last time I played with Miata suspension was back in 2002ish so I'm still playing catch up... on that car I ran RB springs and Konis. I just installed Ohlins on my 01 because those were what I lusted after back then.

The RBs we slightly stiffer than stock and with the sways would do about 1.05g on a skid pad. That was "good". Even on Kumhos I never felt undersprung but I guess I could have been living on the bumpstops.

The Ohlins are almost 3x stock I believe but are still 3-400 lbs softer than the current hot setup. Doing the math on a non-downforce car this seems over sprung.

Can someone explain to me or point me to why it's not?

Do it feel good?

If feel good, is good.

Good.

What do you mean by "doing the math"? Tire tech has come lightyears in the past 20 years, so suspension has definitely gotten stiffer to compensate. But a lot of the hot setups with 800-1000lb/in springs people around here speak of are for track use where grip is going to far exceed anything you'd find on public roads. But yeah like Concealer rights, if it feels good, go for it.

If you are using it for roll resistance why not use a larger bar? I can understand it for high downforce cars but 1000 pounds on a 2400 pound car seems le alot.

Check out some of Emilio's commentary on roll centers. A lot can be had by not lowering the car. The lower you go, the more spring you need to both control roll, and keep off of the bump stops.

Roll in and of itself is not bad if camber curves are strong, as they are on the Miata. The issue remains that if you roll enough to ride on the bump stops, then you have failed.

DNM

This. At stock ride height, the suspension geometry naturally resists roll. Lowering the ride height to optimize center of gravity and camber curves means giving up some of that natural roll resistance, thus demanding higher spring rates. Plus as I mentioned before, tire tech has come a long way in 20 years, and most of the people running 900+ lb/in springs (yes, even on 2400lb cars without massive downforce!) are usually optimizing for 245s or even 275 hoosiers on track, which give a tremendous amount of traction. Traction levels and less natural roll resistance is what leads to spring rate; spring rate is the outcome, not the input.

For a street car on <245 200tw tires 750lb/in is gonna be fine 90% of the time. Theres also huge range of personal preference for people not chasing lap records. If it feels too stiff, go to something softer. For a street driven weekend/HPDE car it really doesn't matter.

In the "sane" realm of spring rates (for the purposes of this discussion, i'm going to pick an arbitrary number of 900lbs, simple because that's what i run and am familiar with), comfort comes more with having appropriately valved quality shocks and sufficient travel, than it does from picking your spring rate, itself.

900 is definitely less comfy on Xidas than 700, but it's still pretty good. 700 is magic carpet.

I've run on two different cars in the last couple years, ranked in terms of comfort. I would call all of them "comfortable" without hesitation. The biggest "knock" against scenario #4 is that you could put anything on that car and it still wouldn't be anything you'd want to drive more than a couple hours at a stretch. It's loud, hot, and not water tight. Rides nice though.

1) Whitener-valved Bilsteins with 700/400 (this is my current street car setup, it's positively ridiculous how smooth it is)
2) Xidas 700/400
3) Whitener-valved Bilsteins with 850/500
4) Xidas 900/500

The bolded section isn't doing the math. You're ignoring motion ratios and impact forces. If you're going to try to do the math to calculate spring rates, you need wayyyy more information than you've got right here. But ultimately, we find that tuning based on performance data and feedback from professional-level drivers results in a better setup than simply doing the math.

Keep in mind that larger sway bars only help with roll, and have a negative effect on ride quality. Anything that impacts the right side of the car gets transmitted also to the left side of the car. Using stiffer springs to reduce roll also reduces pitch/dive, and what impacts one side of the car doesn't automatically get transmitted to the other side of the car. This is the primary reason we use high spring rates rather than over compensating with huge sway bars.

Ride quality - which, to be clear, is usually what people feel as impact harshness - has more to do with how the dampers are valved than it does with what spring rates are used. High spring rates are easily overcome by the force of a harsh bump and the suspension can still soak it up as long as the damper allows it. Stiff springs will result in a busier ride, but not necessarily a harsher one when paired with good damping suited for the rate.

Your correct a motion ratio of .682 I believe and 520lbs or so unsprung at 450lbs/in gives a frequency on 2.0. That is the math.

Im also all for not reinventing the wheel and using what works, but I also know this car has been in development for 30 years and the 949 guys and have done some actuall testing that might help understand why.

I also know that drivers can compensate for a lot and preferences can drive set up too... so I was hoping some could actually explain why and not just "because"... Im actually trying to learn.

lastly I didn't include the inputs or math because I wasn't looking to defend the lower rates, but rather understand the higher one .

The portions that matter are:

A) Does it go faster?
2) Is it easy to drive?
iii) do it ride gud?

The move to higher rates are "because they're better." A calculator wasn't used to get there. A stopwatch was.

The way this discussion was started isn't going to end with the answer you want. The answer you want is the one you already figured out when you did the maths. Now all that remains is for you to accept that the results are good.

How does frequency relate to goodness? How is this metric even relevant? Please explain.

Supermiata.

The testing procedure is just what I outlined. It's not math on a spreadsheet, it's put a setup on it and drive it, tweaking based on data and driver feedback.

Tuning based on feedback from skilled drivers yields better real-world results than math. Math just gets you to a starting point.

this does a better job than I would

That video looks like some M.net shit.

Saw green spring, didn't click.

We only accept blue or red springs here.

This. 100% this.

I immediately closed the video as soon as the presenter stated he authored a book called "custom air suspension".

Found a picture to summarize this threat for people catching up.
https://i.imgflip.com/zskqa.jpg

this

I'll leave this with an article of a GTI driver looking to find spring rates for his car... same logic and no green springs.

https://drivetribe.com/p/lets-talk-s...T--og-IglpbxVQ

Naw dawg.