If you might have noticed, John's pretty heavily into what injurneer folks would call an "empirical-based" mindset on tuning shit. The big difference between a legitimate empirical-based mindset for setting up cars and just slapping shit on comes in having found people to ask with a clue for a starting point (not most forumites on mainstream sites) and then testing (which most forumites on mainstream sites haven't done either). For rally in North America, it's a pretty damn good approach honestly - I don't think there's really much of anyone on this continent that has both rally experience of a sort to legitimately have useful insight, and enough engineering ability to come up with a theoretical model of what the hell is happening on gravel, who isn't trying to charge an arm and a leg for it. And there's all sorts of opportunities for tuning yourself into a blind corner starting from a theoretical basis even on tarmac.

I spent some time sorta reverse engineering what was published on older Group N style Subaru suspension setups, back when the dampers were mostly doing dampery things rather than being the major factor in body control. From what I can recall, the ride frequencies were right around 1.6hz front, and 1.8hz rear, maybe less; I think my notes are from a later iteration when I was homing on a slightly stiffer setup for street use. The point is though that stuff ended up in the sort of ride frequency zone used by cars with fairly mildly upgraded spring rates - hell, the old style Impreza rally spring rates were almost identical to the US STI stock spring rates, just with more travel. Incidentally, from looking at some of the stuff John bases suggestions for some sorts of cars on (Sierra prep book stuff) the wheel frequencies for that are similar too.

I don't know jack about Evo X spring rates or ride frequencies or the like. I'm also not totally sure what you have in mind as far as "tarmac" use; if you want something on the order of what brits seem to call "fast road" just throwing sways on could work. For the dual-purpose (rally/roadrace) thing I'm planning out, the spring rates are probably going to be enough different to warrant different dampers for each setup, but then I'm not a fan of ginormous sway bars.

Thanks for the reference, Steve. I have not read Olley's book and will get a copy ASAP. And thanks for understanding where I'm coming from. When I set up the road-racing car, I did a bunch of math (and measured the entire car and built a model of the entire suspension), but only to get close. Actual practice showed me that the math wasn't entirely correct and I needed a bunch more front spring to keep the car from being terrifyingly loose at speed. I am trying to get close enough here that the adjustability of the shocks will allow me to swap springs during testing. That's why I started all this with the question of whether I need to be thinking about the bars when deciding on initial damping. I wanted to make sure that, if I really do take a softly-sprung car and slap on huge bars for tarmac, the same shocks will still be (vaguely) appropriate.

And, bingo! on the idea that trying to have a discussion like this on NASIOC or EvoM is a complete and utter waste of time. I have tried on both and several other sites, as well.

As to how to describe things, I'm completely open to the possibility that what I'm used to isn't what is generally used. It's funny. When I started playing with the math about 15 years ago (again, for tarmac only and mostly autocross then), spring-rates were always in pounds/inch. When I switched to the Evo, I was suddenly faced with Kg/mm all the time, maybe because there are a lot more Evos in eastern Europe than Britain or the US. I've only just recently gotten used to talking in "kays" and now I get to (have to?) go back. I should have known, because the guy who fabbed the brakes was always asking me to say it in pounds/inch and not Kg/mm.

Butt hurt? Please. That was what passes for sarcasm from me. You're a difficult person for a newbie to the site to deal with, John. Anyone who reads a lot before joining into a conversation here will not have a neutral opinion of you. I would love to get help from you and everyone else. But this is a hobby for me and it's supposed to be fun and one part that I enjoy a lot is the math and theory behind set-up, so if I stop enjoying our back-and-forth, I'll just ignore you. I apologize in advance is that comes across as rude.

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mekilljoydammit
From what I can recall, the ride frequencies were right around 1.6hz front, and 1.8hz rear, maybe less; I think my notes are from a later iteration when I was homing on a slightly stiffer setup for street use. The point is though that stuff ended up in the sort of ride frequency zone used by cars with fairly mildly upgraded spring rates - hell, the old style Impreza rally spring rates were almost identical to the US STI stock spring rates, just with more travel. Incidentally, from looking at some of the stuff John bases suggestions for some sorts of cars on (Sierra prep book stuff) the wheel frequencies for that are similar too.

The little that I have found in the last few days matches this. The one thing that wasn't clear was whether these are ride frequencies based only on the wheel rates or whether they took the tires into account. Maybe what I'm missing is that the effective spring rate of gravel tires is so frickin' high that they are simply ignored. That would make some sense to me, given what a nightmare it was trying to get the old KM6s off the Braids using a standard tire-mounting machine.

In any event, the more I read, the more I think that 5k springs ... oops, 280 #/in springs ... would be better than 336, but only if the car never leaves the ground or has very nice bumpstops.

Do people ever use progressive springs on gravel?

A rule of thumb I once came across said that for springs in series, if one spring is 10x the rate of the other you can just think of it as solid for pretty much all intents and purposes and move on. Don't know what spring rates on rally tires are like, but for some street tires and the 1.6/1.8hz spring rates, I was looking at at least 5x, which is probably fawking close enough. Un-scienterrific, but what the heck.

I know there was talk about Mazda using progressive springs back when they were in WRC, and probably some others. There's also various setups using helper springs which is sortakinda like progressive, ish. It may not be a bad idea at all, but as far as I can tell, the trick with progressive springs is getting proper ones (taper ground wire and so on) in rates you want for reasonable bucks.

Perspective I came across on here regarding bumpstops and the advisability of hitting them is... well... soaking up really big bumps is what they're for. Is it better to tune the rest of the suspension so you stay off bumpstops over occasional big jumps, or deal with things having a sharper jolt from hitting the bumpstops, but have spring rates and so on better tuned to the rest of what you're driving on.

... but I'm just an injurneer who's been doing research and seeing what people say and figuring out why it would work - I've driven a grand total of zero stage miles, so grain of salt and all that.

IIRC the Ford Sierra book references some progressive springs for some conditions...

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KF7RWG
http://www.utahrallygroup.com

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mekilljoydammit
A rule of thumb I once came across said that for springs in series, if one spring is 10x the rate of the other you can just think of it as solid for pretty much all intents and purposes and move on. Don't know what spring rates on rally tires are like, but for some street tires and the 1.6/1.8hz spring rates, I was looking at at least 5x, which is probably fawking close enough. Un-scienterrific, but what the heck.

I know there was talk about Mazda using progressive springs back when they were in WRC, and probably some others. There's also various setups using helper springs which is sortakinda like progressive, ish. It may not be a bad idea at all, but as far as I can tell, the trick with progressive springs is getting proper ones (taper ground wire and so on) in rates you want for reasonable bucks.

Perspective I came across on here regarding bumpstops and the advisability of hitting them is... well... soaking up really big bumps is what they're for. Is it better to tune the rest of the suspension so you stay off bumpstops over occasional big jumps, or deal with things having a sharper jolt from hitting the bumpstops, but have spring rates and so on better tuned to the rest of what you're driving on.

... but I'm just an injurneer who's been doing research and seeing what people say and figuring out why it would work - I've driven a grand total of zero stage miles, so grain of salt and all that.

I'll ignore this guy but there are lots of lurkers so, EVERYBODY has run progressively wound and/or true taper ground wire progressive springs straight wound and progressive..

And while the I have always maintained that we must keep our politics progressive, we should---unless we want to waste incredible amounts of time and money----keep our springs linear..

UNLESS, one has access to piles and piles of different sorts of progressive springs for free....

And even thinking about the spring rates for tires, I have only one word: what a waste of time.

Somebody need to understand that the 2 worlds of gravel and tarmac have 2 seriously different overarching goals: Gravel is the search for grip; asphalt is the search for handling...

The whole premise here isn't really looking for answers, or it would have been approached differently. It is about affirmation of a plan previously decided upon...

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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john vanlandingham
The whole premise here isn't really looking for answers, or it would have been approached differently. It is about affirmation of a plan previously decided upon...

I am tempted to argue about this, but why argue about something when neither party really gives a hoot? So, instead, I'll just ask you how you would approach the problem.

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Iowa999
I am tempted to argue about this, but why argue about something when neither party really gives a hoot? So, instead, I'll just ask you how you would approach the problem.

I still haven't figured out what the problem is.
In my experience you can either unbolt it and remove it altogether, unbolt one side and leave it there, or just get pissed and cut it in half altogether.
I would highly recommend leaving mathematics out of it.

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Grant Hughes

Just out of (morbid) curiosity, if I were to tell you that a bone-stock Evo X gets about half of its single-wheel rate and about two-thirds of its roll rate from the swaybars, would you say "yeah, I knew that," "wow, that's rather a lot," or "who cares?"

Street cars do that. It's probably also tuning things such that it's hitting the bumpstops a lot sooner than you'd expect too.

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Iowa999
Just out of (morbid) curiosity, if I were to tell you that a bone-stock Evo X gets about half of its single-wheel rate and about two-thirds of its roll rate from the swaybars, would you say "yeah, I knew that," "wow, that's rather a lot," or "who cares?"

That's a definite who cares.
Did you know that the USA got 2/3rds of it's roll rate from Subarus. Travis and Ken were definitely the biggest contributors for a while there...

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Grant Hughes

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NoCoast
Did you know that the USA got 2/3rds of it's roll rate from Subarus. Travis and Ken were definitely the biggest contributors for a while there...

OK. That was funny. Thanks.