Rhode_Dog

Excuse my ignorance, but my knowlege of the suspension related is very basic.

I read some good threads that discussed ideal spring rates for coilovers. But there is a question I wanted to present in this particular forum

Why the Equal Spring Rates?

Knowing that an ideal spring rate for the FD is that of a higher rate in the front than the rear. So why do so many high priced coilovers from Japan come with equal rates? Is this simply a by-product of the drift fetish or are they on to something that we are simply behind the times on?

rynberg

Drift fetish, I would guess. As an experiment, I am running 600/550 rate springs. The car just has too much oversteer, even with running a staggered tire setup (235/265) and the smaller 95 rear anti-roll bar.

What really makes me laugh is that most of the coilovers coming out are running over 650 rate springs front and rear. What a joke.

azn akira

i dont think its a drift fetish. the fastest time attack fd's in japan run equal spring rates or higher rates in the rear. also most dont stagger their tires, they tend to run 255s all around.

i have kei office xr coilovers with 16/14kg/mm springs so roughly 899/787. the ride isnt harsh at all. the dampers on the coilovers are really good because i've ridden with tein and jic with lower rates and the ride was complete crap. i drive my car a lot in the mountains and even over rough road the tires stay firmly planted to the ground. im almost done putting my new motor in so i should be at streets of willow in a couple months (depending on school and work schedule) so ill see what its like there.

aznpoopy

it's not drift fetish.

what feels 'neutral' to a race car driver feels incredibly tail happy to a regular amateur driver.

what is 'ideal' in terms of suspension changes depending on the skill, experience and personal preference of the driver.

Pat McGroin

Exactly. Best bet is to call a company and tell them what you want to do, they'll suggest some spring rates, drive those on a track and go from there.

OC_

Do you FD guys disconnect your rear swaybar for those equal rates? I know theres a lot of FC guys that do that when the rear rates go up.

RETed

I'm actually surprised that they do offer front and rear equal spring rates...
Can you tell us which models do this?
I don't recall any of the HKS / A'PEXi / Tein / Cusco stuff ever having done this.
It used to be a rule of thumb NOT to do this to minimize oscillating front to rear or porposing of the chassis.


-Ted

azn akira

well i think because the motion ratio is different between the front and rear the wheel rates will still be different with equal spring rates. so oscillating isnt an issue. just a guess.

i know amemiya uses 16/18 kg/mm springs
apex n1 is 16/16
axia sports pro is 16/16
zeal super function is 16/16
kg/mm dns is 10/10
feed is 18/18
ohlins is 14/14
feast is 12/12

there's a bunch more

rynberg

1. No one here is a race car driver.

2. No one here only drives their car on a glass smooth track.

3. You don't know what other things they've done to the cars suspension wise.


There are a lot of experienced track guys here that have done a lot of experimenting with spring rates -- guess what? NOT A SINGLE ONE runs even spring rates. It's insane. The rear suspension has a higher wheel rate than the front, therefore equal spring rates = higher wheel rates at the rear = oversteer.

azn akira

just because no one in the us does it doesnt mean it doesnt work. im pretty sure re amemiya, feed, pan speed, etc have more racing experience than just about everyone combined on this forum. ill bet with re amemiyas experience in jgtc he has the data, and experience to justify using higher rear rates. those time attack cars are fast and all business, they dont play around with drifting. maybe with the right downforce, lsd, and various other suspension settings it makes a better package.

exactly. which is why you cant call running equal spring rates (or higher spring rates in the rear) insane. you dont know how the shocks are tuned, or the stabalizer bars, or anything else for that matter.

maybe with the extra downforce, lsd settings or for some other reason they need a higher rate in the back for more corner exit oversteer to neutralize the handling?

so, my 16/14 kg/mm rates are fine. if you are ever in santa barbara ill let you drive my fd. i bet you wont think its too stiff

DamonB

And I'll bet not a single one of them are running anything resembling a stock car, but instead a specially prepared racecar with custom chassis and suspension components.

The front vs rear wheel (and therefore spring) rates are fundamental to the front vs rear load transfer. Since the wheel rates are fundamental to what the chassis does shocks, stabilizer bars or anything else for that matter will have no effect whatsoever on front vs rear load transfer.

If the car makes a lot of rear downforce then a higher rear spring rate would be needed to maintain chassis rake at speed. Again, no road driven car is ever going to run into this problem regardless of how big their goofy wing on the trunk lid is. Road cars make no where near the downforce that specially designed and prepared circuit cars do.

azn akira

you'd be surprised how stock suspension wise most of these cars are. most of them are just coilovers and stiffer bushings. you could build a lot of these cars with the products they sell. a lot of these cars are built to show what you can do with their products

i didnt know we were talking specifically just road cars. i was trying to come up with a reason why they might run high spring rates in the rear

Rhode_Dog

Damn, gone for a day and we have this mnay responses. Normally the threads I start don't get much response. Awesome feedback guys.

It would be interesting to see what else is done to those specific car running those high equal spring rates, in terms of suspension and chassis modifications.

azn akira, I look forward to seeing what kind of feeback you will have once you track your car with those spring rates.

rynberg

Just because the car doesn't have much body roll and feels responsive doesn't mean it handles better. Tell you what. Instead of me coming down to Santa Barbara and riding in your car ON THE STREET, you come up to Buttonwillow and run hard through the esses. Then we'll see if you think those spring rates are too stiff!

Why would anyone put on 16/14 spring rate coilovers for a street driven car? It just doesn't make any sense. Some of you guys need to quit blindly worshipping the crap that a lot of JDM companies are selling and actually learn about the parts you are buying.

azn akira

well i do want to run button willow sometime, so when i have the time and money ill shoot you a pm. i wasnt asking you to come down, i was just saying if you were ever in the area you could swing by.

because its really not that stiff. the ride is not bad at all. the motion ratio for the front suspension on the fd is .6 right? so the wheel only see (.6^2x899) like 5.79kg/mm right? i am not blindly worshiping jdm companies. the rx7's they prepare are fast, no question about that. some of those fd's held records at various tracks in japan. like it or not those spring rates work for them, and help them get very low times. im not saying that everyone should go buy them, i was just trying to show that they dont use those spring rates because of some "drift fetish". fyi not every japanese likes drifting, just like not every american likes nascar.

sereneseven

LOL

"The front vs rear wheel (and therefore spring) rates are fundamental to the front vs rear load transfer. Since the wheel rates are fundamental to what the chassis does shocks, stabilizer bars or anything else for that matter will have no effect whatsoever on front vs rear load transfer."

rynberg, sorry to pick on you but this is a gross over simplifiction of whats going on... your argument only has merit if the vehicle you are describing is a train. load tranfer on a car is affected in variable amounts by any and all of the following when a car is asked to accellerate in more than one direction. tires,arb's,spring,bump rubber,shock pressure,chassis all of which affect each other....say your car is ballanced with a 100lb split on spring with equally spring rated tires then you change to a set of tires that have a 100lb split front to rear....guess what you end up having to run different spring rates to regain a nice balance.

oh...i was going to go on but then i realized we are all just talking about a street car and regular people who drive cars on the street... and well the springs that work well in downtown san francisco are going to handle like **** at sears point just like the springs that work well for anyone here are going to handle like **** for say... (name any profesional driver).

sereneseven

^ sorry rynberg I meant Damonb

DamonB

It's not a gross over simplification. I said the wheel rates are fundamental to front vs rear load transfer but admittedly used the wrong word. "Balance" is what I was thinking in my head; "load transfer" was wrong. My mistake. The load transfer would be the same regardless of any of these things.

I've corrected my mistake, you need to correct yours. Load transfer is the same regardless of tires, arb's, spring, bump rubber, shock pressure. Load transfer is strictly a function of CG height, track width and wheelbase. Nothing else will change the amount of load transfer.

The single most important factor in front vs rear balance of the car is going to be front vs rear wheel rate, that's why I said it was fundamental. An ARB for instance changes wheel rate only when the chassis experiences roll. Even in this instance the ARB acts through the springs so again the springs are the most fundamental element. You can't create wheel rate with only an ARB; there must be springs in place at the corners as well.

sereneseven

Damonb, i'm not sure where you are pulling your information from but you are misinformed.

facts: tires, springs, shock pressure/valving, arbs ,chassis rigidity, bump rubbers........all affect both the rate and the total amont of load transfer a vehicle experiences when being driven.

"An ARB for instance changes wheel rate only when the chassis experiences roll. Even in this instance the ARB acts through the springs so again the springs are the most fundamental element. You can't create wheel rate with only an ARB; there must be springs in place at the corners as well."

ARBS DO HAVE WHEEL RATES JUST LIKE THEY HAVE A MOTION RATIOS!!
do think race teams go to K-rigs and seven post shakers with just springs the answer is no?!?!?! gues what teams also spring rate check all of the above mentioned components for the simple reason that they all affect......LOAD TRANSFER which is what affects.......the cars BALLANCE.

who cares what a cars balance is in a strait line??? I am assuming that by balance you are refering to the oversteer understeer charicteristics of the car which all accur during cornering which=body roll. do you wait until you are in a strait line before you hit the gas pedal the answer i hope is no.

shock pressure has a spring rate
bump rubbers have spring rates
tires have spring rates
ARBS have spring rates

all are asked to support the mass of the car during different events.

gracer7-rx7

iTrader: (16)

um... you talking spring rates or rates of compression for the different components you mentioned??

i'm no expert but last i checked rubber (as in shock tower bushings for example) does not have a spring rate but rubber does have a hardness value that relates to how much it may compress.

in any case, the discussion is about running equal front and rear springs rates which I think all posters agree is not the optimal setup for the FD.

DamonB

Nope.

Nope.

The equation for lateral load transfer is:

Lateral Load transfer= (G*CG height)/track width

Where
G = cornering G
CG = center of gravity

The equation for front/rear load transfer is:

Load transfer= (G*CG height)/wheelbase

Where
G = acceleration or braking G
CG = center of gravity

You'll notice these equations don't include tires, springs, shock pressure/valving, arbs, chassis rigidity or bump rubbers because those things have no effect on load transfer.

The ARB's themselves do not have wheel rates, they can only increase the wheel rate when springs are installed. For instance the maximum anti-roll rate any ARB can add is the sum of the wheel rates at that end of the car. Since the ARB acts through the springs even an infinitely stiff bar would merely collapse both springs, so the maximum anti-roll is always limited to 2X the wheel rate. Again the springs are the most fundamental element because the ARB must act through the springs.

You're right, but those things have nothing to do with the amount of load transfer the chassis will experience in any situation. Spring rate and load transfer are two different things and load transfer is never effected by spring rate. If spring rate changed load transfer you could make your car lighter by installing softer springs.

Read:

Racecar Vehicle Dynamics

The Physics of Racing by Brian Beckman Weight Transfer

Everything about Sway Bars by Grassroots Motorsports

Dynamic Load Transfer

sereneseven

damonb, SORRY i miss read your response and then got lost myself on the load tranfer terminology. i am 100% in the wrong load tranfer is not effected by any of the above stated, balance is.

my point was that true wheel rates are cumulitive figure of more than just the springs and in many racing applications other components can be just as if not more fundamental to the ballance of the car . therefore there is no argument that equal spring rates wouldn't work.

Fritz Flynn

iTrader: (263)

I agree depending on the setup equal spring rates could be appropriate and more effective.

I think equal spring rates would work fine on a FD. Usually when entering big fast corners I get understeer followed by oversteer and I'm guessing stiffer rear springs would fix this problem. However it would make the car more difficult to drive so for the everyday hack stiffer front springs are the way to go so you have more time to catch the car. Most people even pro race drivers like a little understeer followed by oversteer for a road course driving.

ptrhahn

iTrader: (9)

A discussion on what's used on racecars in Japan isn't really that applicable, since a race team would tailor their spring rates for each track.

If you've got to live with one rate everywhere.... slow tracks, fast tracks, tracks with elevation change, tracks with bumps... oh yeah, and street driving... that all adds up to.... compromise.

I would think I could get away with rates that are much closer F/R at a track like WGI than I could at Summit Point or VIR.... WGI is all fast sweepers, whereas Summit has a couple places where you need the rear to dig in under power. Likewise, I probably don't need a 285 front tire at The Glen either, but I sure love it through the carousel at Summit.

sereneseven

I had hoped this thread would just die away...do to me making an *** of myself erlier in it. but since its come up again.

Be it in japan or here has no relevence. an argument was put forth that the rx7 need's softer springs in the back. and my point was that statement was untrue. granted a stock car with stock tires and the original test drivers and road conditions this my be true, but chances are anyone who is looking into this has changed many things on there car from stock and thusly there is no reason that someone my indeed find it a benefit to try stiffer rear springs.