motoxxxman

So I'm finally going to be getting some coilovers for my car which is built mainly around autocross and track racing, but will also see the drag strip on rare occasions, and is often a DD when my jeep is down.

As the title states, what is typically a good front/rear spring rate ratio compared to vehicle weight distribution ratio? my car is a cool even 60/40 weight distribution.
if different ratios are better for different types of racing, please mention that as well.

Tyson

it depends more on what you want to do with the car. your list of examples pretty much says generic use.

start with standard rates and change the rates as you need/want. you wont know until you try.

B serious

iTrader: (1)

^yep. Spring rates take a bit of trial and error via actual experience.

Mystery car, though. Very mysterious. So shrouded in mystery.

motoxxxman

ok, I'll say specifically for autocross. is there a relation between weight distribution and spring rate front to rear ratio that commonly works best for autocross?

IE: because my car is 60/40 weight distribution, would I want a 60/40 ratio between spring rates? or should I go more like 55/45?

not really, it's in my sig.

TunerN00b

You're on the right track, but still looking at it wrong.

Spring rate is, honestly, rather useless to worry about in and of itself. It is the wheel rate that actually matters.

And if you want to work wheel rate and weight into the same equation, then you're discussing suspension natural frequency.

So, in a theoretical world, if you wanted a balanced car, you would aim for balanced suspension frequencies front and rear. However, doing this has the horrible effect of causing the car to oscillate poorly over bumps in the road, so a difference of at least 10% is desired.

And in the end, you'll do a ton of math, only to find out that all it really gives you is a starting point that you still have to trial and error adjust from anyway. Which returns back to Tyson having the correct advice.

B serious

iTrader: (1)

I can't see sigs because I'm using the mobile site.

Anyway....balance, imbalance, or whatever ratio is determined by driving the car and finding what works for you.

Otherwise everyone that autocrossed a (insert car here) would have the exact same setup and there wouldn't be any advice to give.

You use spring rates for your car's wheel rate, setup, and quite a few other considerations. Its an incredibly complex answer and everyone will have a different take on it.

Just drive it. Want more rotation? Want to just use spring rates to do it? Stiffen the rear springs. Want to do it via other methods? Need to fine tune it? Play with the sway bars and shocks and tires and tire pressures and driving style.

Tyson

let me be more direct.

stop thinking about it in weight distribution. it doesnt work that way. its quite stupid to be honest.

a 200/400 spring rate is not the same a 800/1600.

consider the front and back independent and learn how to tune the car to get the whole car to do what you want, along with the tire pressures, shock valving, etc.

want to know where to start? drive it first.

motoxxxman

I'm well educated in all aspects of what affects what regarding bars, tire pressures, alignment, and damping. I also have many years of season championships under my belt, all but one that I won the championship too. Spring rate is the one thing I know very little about though and I'm ready to upgrade that department as a whole in conjunction with adjustable dampening of course.

of the coilovers made for my car, these are the spring rates available without going custom, at least for the kits that actually list the rates:
f10k/r5k
f12k/r6.2k
f18k/r8.7k
f22k/r18k

I find it odd for my 60/40 balanced car to have most of the kits use rates that are 65/35. I'm about to go measure my LCA's right now to see what the wheel ratio is

what confuses me too is I constantly see the civic guys talking spring rates and they always claim the rears are stiffer than the fronts. Is that actually the case? or are 80% of them just fools?

B serious

iTrader: (1)

Well....this went nowhere.

motoxxxman

you're right, because no one is giving any helpful information besides "drive it, change springs, drive it again, change springs, drive it again, see what works best". thats not a helpful answer. how many people do you know that have coilovers and 3 or more different sets of springs for them?

there is always a guideline for stuff like this, typically involving some math. I'm just trying to find said guidelines

so back on topic, I measured my lca's:

front: inner pivot to bj: 14.5", inner pivot to strut pivot: 11.0"
ratio: 1.318 (or 0.759)

rear: inner pivot to bj: 17.0", inner pivot to strut pivot: 14.0"
ratio: 1.214 (or 0.824)

someone has to know something about spring rate math...

B serious

iTrader: (1)

Its not going to help you. Its just going to give you raw data. *Most* people use a rear-biased setup for autocross and track use.

Do you at least know what your current spring rates are? What is the car doing or not doing?

motoxxxman

current setup is not even worth comparing haha. cut stock springs (1.5 coils removed, while submerged in cold water) on oem struts with over 300k miles, somehow still no leaks and full of oil, but definitely softer than new. stock front bar, a few strips of angle iron welded to the rear bar. it actually handles incredibly well and is very well balanced. just waaaay too soft in both spring and dampening. I'd love an actual aftermarket rear bar, but the only one that was available was whiteline, and it was discontinued a few years ago.

by "rear biased" you mean they run it a little stiffer in the rear?

I did some math and found that between my weight distribution and suspension geometry, I'd have a "level" stiffness with 10.6k front and 6.2k rear. the kit I'm considering normally comes 12k front 6.2k rear.

and if you can't see my sig still, it's a 1990 prelude, turbo b20a/b21, 300whp 290tq, helical LSD, sunroof removed and covered with aluminum sheet, and some other misc weight reductions. current curb weight when race prepped is 2330lbs, 60/40 weight balance. 100lbs heavier when street driven, currently planning a little more weight reduction, prob down to 2200lbs when race prepped

motoxxxman

pics for reference. the black one is my old chassis, I have everything swapped to the non-rotted blue one now, identical in every way.

B serious

iTrader: (1)

I'm not sure anyone is going to be able to help you much, bud. There are a lot of off the shelf systems you can start with. Drive it. Feel it out from there. People have already used math to get the base/off the shelf rates. So...you try that and then deviate from it as you need to. That's how everyone from Hillbilly Racer Hank to Louis Hamilton does it.

Why do you want different springs in the first place? What is the car doing wrong? Or what do you want it to do better.

TunerN00b

If you're going to insist on going down this path, it is time for you to make use of search.

And in doing so, you'll find threads like this:
https://honda-tech.com/suspension-br...ation-2566270/
and this:
https://honda-tech.com/suspension-br...r-dc2-1758952/

Where the best advice is still the best advice
A decade later, it's still 100% truth.

All of us who are willing to fine tune to go faster. It's actually rather cheap and simple. Use spring perches that allow standard sized race springs, and then buy used Eibach ERS, Hypercoil, etc... Sell off what didn't work to the next person going through the same process, and only be out the cost of shipping for the trial.

I think I paid $50 shipped for the last pair I bought...

motoxxxman

because I'm on cut stock springs, and oem struts with a 300k+ miles. I think that's pretty self explanatory lol. I want much less chassis movement in all directions, and stiffer/adjustable damping.

Tyson

The worst thing is that you don't want to learn anything. So I'm out of this thread.

motoxxxman

the worst thing is assuming I'm ignoring the comments that have been posted.
and even worse, actually thinking I dont want to learn. I wouldnt have asked to begin with if I didn't want to learn.
and I've been using every resource posted so far, as well as many others I've found on my own.

problem is, noone has any actual insight into what they personally experience for common starting points and guidelines.

just because I made a comment of "how many people do you know that have multiple sets of springs for their coilovers?" doesnt mean I don't intend to buy additional springs. I DO however need some sort of baseline, and have been taking everything into account, from here, from google, from fellow racers, and more.

maybe try giving some useful info so I CAN learn. I can't learn if noone will teach me. that is the whole purpose of this entire website, isn't it? to learn and to teach?

motoxxxman

I have been studying these and their content and contained links, and anything related to them since the moment you posted them, and I am learning a decent amount now. thank you.
any other insight is highly welcomed, from anyone

KoRn_vIRuZ

Yes, weight does influence spring rate selection. All else being equal, the lighter the corner weight, the less spring rate you need to achieve a given ride frequency.

In practice though, you have to account for the suspension motion ratios and relative roll stiffness front to back. In a FWD application you want to have most of the weight transfer occurring at the rear of the vehicle to maximize front end grip. This is why many people run disproportionally stiff springs (or anti-roll bars) in the rear.

If you want to get technical and understand why this maximizes grip, you can read the spring and damper white papers on this site, they are really great: Technical Papers - OptimumG

I created a spreadsheet out of those articles.

motoxxxman

excellent, thank you.

any insight into the whole concept of frequencies? I know what it is, and everyone keeps talking about it, but what are some things to factor in that are heavily dependent on wheel frequencies?

IE: at one point someone said you don't want matching front and rear frequencies on the street. but why? and what are the effects of higher frequency up front vs higher frequency out back?

KoRn_vIRuZ

Please read the articles on the Optimumg site, they explain those concepts better than I could.

TunerN00b

Super high level answers, because anything else would require a ton more information than is here.

Desired ride quality, road surface quality and conditions, and tire characteristics.

The first is self explanatory.
Too stiff, and you have traction issues over less smooth pavement.
Too stiff, and tires with softer sidewalls have the sidewall become the primary spring, which is undamped, and you lose traction as the car bounces on the tires.

Higher front means more understeer.
Higher rear means more oversteer.


Of course, this is ignoring swaybars, which can have a substantial effect on the overall picture. Shock valving too. And driving style. And tires. And, and, and...

I went down this path. In the end, I asked someone with a similar chassis for a suggestion for starting spring rates, got used to them, then made minor changes to address a specific desire. Lather, rinse, repeat.

motoxxxman

thank you, I've begun to gather that info from all the links I've been researching and reading. I also need to get on a drive-on lift and get more accurate measurements of my lca's and shock/spring angles for more precise calculations