DC2R Coilovers Spring Rates Ratio F/R

[anzai]

hey guys i've been wanting to upgrade my spring rates for a while now and had a good read on sussy setups for dc2r for street and track

stock 98spec dc2r rates:

front - 4.5kg/mm
rear - 2.5-4.5 kg/mm (progressive)

i understand that when upgrading to coilovers with higher rate springs, it's best to keep the ratio similar between the front and rear rates to reduce unnecessary understeer or oversteer.

but as the rear springs are progressive, im not sure of what ratio to use.

most people in the states recommend a 50lb/in difference between the front and the rears, for example:

front - 500lb/in ~ 9 kg/mm
rear - 450lb/in ~ 8 kg/mm

is this a good ratio?

cheers

[tinkerbell]

i ran 12/8 & 10/8 and now 14/10

but i have a larger rear sway bar, this means i run can softer rear springs...

they were all good combo's once dialled in...

are you going to be running a coilover setup?

the stock shocks wont cope with such high rates...

[anzai]

yep coilovers, custom spring rates

with stock rear sway bar, stock bushings, possibly be getting ultra racing rear strut brace

im thinking 10/9, or should i get 10/8 with the rear strut brace?

[tinkerbell]

do you prefer oversteer, or how do you want to control the car?

what brand coils?

[anzai]

well stock dc2r is supposed to have a little tendency to understeer

so im thinking if i stiffen the rear a bit i'll be able to neutralise it

what would you suggest?

[tinkerbell]

well stock dc2r is supposed to have a little tendency to understeer

so im thinking if i stiffen the rear a bit i'll be able to neutralise it

what would you suggest?

DC2R has a tendency to understeer? does yours feel like that to you?

my suggestion would be to go something 'normal' and tune it to your liking on the track...

springs are cheap anyway, but 10/8 should be OK as a starting point...

[EG30]

Is ride comfort impt to you?

What sort of ride height are you intending to run?

Daily driver? Track car often?

What type(s) of tyres are you intending to run?

[tinkerbell]

Is ride comfort impt to you?

What sort of ride height are you intending to run?

Daily driver? Track car often?

What type(s) of tyres are you intending to run?

good questions!

[anzai]

sorry i meant with my setup at the moment the car has a tendency to understeer

i have 6/4 coilovers at the moment

if i want a comfortable ride, i'll sell up and buy a euro. i want my car to feel solid first of all

im running 205/45/r16 at the moment and there's no wheel gap, that's how high it is

it is a daily, but i can't wait to track it

at the moment im running ku31's, and probably will stick to it for a while even for track.

[EG30]

I see 6/4 setup so not much difference to the stock setup effectively at the wheels.

Factory rear progressive-ness very minimal anyway at the wheels, ie feels every bit 4.5kg linear spring rate and a little bit more with pretty agressive damping from factory esp on the rebound side.

We have 10.7kg front and 7.5kg rear on our dc2r on Koni GC setup. Front springs are Kings 600lb's and rears are Eibach that came with GC kit I bought that were at the front. It's a hand me down from my eg racecar which now has Tein Monoflex on 12/10kg springs ( came with 10/6 orig ).

A fren of mine has a dc2r on 8kg/6kg setup, very stock car on stock ride height. That's how he likes it as 10/8kg prev that came with his STD ( coilovers not medical condition ) was too harsh at the rear for his liking.

It's great that you could run your car fairly low, cos neither of us could afford much lower than stock with work and home carpark hump/dip clearance issues with the front lips.

10/8kg good starting point for sure as Tinkerball suggested.

No point trying 8kg/6kg as you prob would be dissppointed; though a large gain in % but in reality at the wheels feels much less.

Are you coils generic sizes? ie 65mm ID and say 175-180mm free lengths?

With your ride height, you have 1.5 deg natural neg camber at front before camber kits?

Dialling out understeer can be achieved also with different ride height at the rear ie more rake, more toe out at the front, tyre pressures and wheel spacers at the front.

With stiffer rear springs you do get the benefit of powering down out of corner better + better launches. More rake would magnify this more.

A thicker rear away bar helps alot as well esp in the feel if not as much as you hope in terms of lap times. We have a Cusco 25mm bar which is effective 2x as stiff as stock 22mm bar and I can't rec them enough. Was expecting a lot more sudden oversteer but the dc2 chassis copes with it a lot better than say my eg with ASR 24mm. The lack of flex of the bodyshell really translate the + roll stiffness at the rear much better than eg and you get better turn in a lot earlier and car takes a set a lot sooner so you can be all ready for the midcorner phase just after you turned in and not having to worry about if the f*ker is going to turn it's nose in towards the apex or the rear is going to overtake the front.

KU31 a great tyre for the $ esp it's almost always on special with at least one tyre chain or another; I use that as my road tyres in my eg racecar and often use that for tuning days at the track to save my R compound tyres. Very easy tyre to drive on with plenty of warning before yielding and with 3 deg neg camber the outer edges are still in good shape after many laps at the track. Their limitation being only good for a few laps before getting very greasly.

You running front and rear camber kits?

[anzai]

goddamn that's a massive reply. if i could rep you i would do it 27 times. thanks mang!

to answer some of your questions:

im not sure about the spec of the coils, but it should be pretty generic

-1.5 natural front camber before camber kits sounds about rate. although im running about -3.5 at the moment to fit the wheels i have now

and yes i do have front and rear camber kits, i also swapped the front uca from L to R to increase caster angle

at this stage i dont intend to upgrade the sway bar as i want to track the car progressively from minimal mods and work my way up from there.

im leaning towards 10/8 now, anything else i should look out for?

again thanks for the massive reply, heaps and heaps of good info!!

[EG30]

goddamn that's a massive reply. if i could rep you i would do it 27 times. thanks mang!

to answer some of your questions:

im not sure about the spec of the coils, but it should be pretty generic

-1.5 natural front camber before camber kits sounds about rate. although im running about -3.5 at the moment to fit the wheels i have now

and yes i do have front and rear camber kits, i also swapped the front uca from L to R to increase caster angle

at this stage i dont intend to upgrade the sway bar as i want to track the car progressively from minimal mods and work my way up from there.

im leaning towards 10/8 now, anything else i should look out for?

again thanks for the massive reply, heaps and heaps of good info!!

wow 3.5 deg neg cam a lot for a daily, I guess if that's what is req to clear your wheels without fender rolling/pumping...

I have the same on my racecar and toe out between 2-6mm total depending on the type of event; it does chop out the inners a lot when I drive car to events esp the far away events up to 400km away from Perth.

With zero toe or 0.5mm total toe out it's fine though with -3.5 camber.

Swapping oe front UCA does gain you castor but f-all really to make a difference. Unfortunately for our cars despite the best double wishbone style setup castor isnt easy to gain unlike macpherson struts where you can tilt the strut back easily with top slide plates; and to a lesser extent the ED/EF setup with castor rod where you can mod them.

Stay away from Crapline castor kit/DIY washers+longer bolt; will cause you no end of consquential problems as I am still dealing with the problems on my racecar. Custom bronze or nylon offset bushings can be made up but far from ideal for road use.

getting used to the new springs rates before changing rear sway bar is a great idea, one should never throw many mods at car at one time and not knowing what did what.

all you need for now is to get the coils, set the rear up 2-3mm higher ( measure at jacking plates with chopped ruler for accuracy ) at the rear to start off with and wheel align and see how that feels after a few tuning days and fine tune rear ride height to taste.

[cordz]

wow 3.5 deg neg cam a lot for a daily, I guess if that's what is req to clear your wheels without fender rolling/pumping...

I have the same on my racecar and toe out between 2-6mm total depending on the type of event; it does chop out the inners a lot when I drive car to events esp the far away events up to 400km away from Perth.

With zero toe or 0.5mm total toe out it's fine though with -3.5 camber.

Swapping oe front UCA does gain you castor but f-all really to make a difference. Unfortunately for our cars despite the best double wishbone style setup castor isnt easy to gain unlike macpherson struts where you can tilt the strut back easily with top slide plates; and to a lesser extent the ED/EF setup with castor rod where you can mod them.

Stay away from Crapline castor kit/DIY washers+longer bolt; will cause you no end of consquential problems as I am still dealing with the problems on my racecar. Custom bronze or nylon offset bushings can be made up but far from ideal for road use.

getting used to the new springs rates before changing rear sway bar is a great idea, one should never throw many mods at car at one time and not knowing what did what.

all you need for now is to get the coils, set the rear up 2-3mm higher ( measure at jacking plates with chopped ruler for accuracy ) at the rear to start off with and wheel align and see how that feels after a few tuning days and fine tune rear ride height to taste.

What is wrong with the Whiteline Castor kit? i ask because it's sitting in my room waiting to be put on :S. I think the shims do look dodge and was thinking getting a custom aluminum bushing made to replace them?

More to the OP, i run 12k and 7k F/R in my DC2R. My rear boot is stripped and i run a rear strut bar. The rear of my car consequently is very stiff, and it complains on the road all the time. The vice of my spring rates is, they are just bearable enough for the street, but just not stiff enough for the track. Fantastic performance on your favorite S bend on the way home though.

If you don't intend on tracking your car, don't go above 10K F or 8K R.

I recommend keeping the rear spring rate low in comparison to the front (i.e 12 vs 7 or 10 vs 6) because this will resist weight transfer to the front under braking, and encourage weight transfer to the rear. I found this solved my car's tendency to snap oversteer when backing off throttle and stepping on brakes, the car wouldn't dive as much thus the rear had more grip.

[tinkerbell]

I recommend keeping the rear spring rate low in comparison to the front (i.e 12 vs 7 or 10 vs 6) because this will resist weight transfer to the front under braking, and encourage weight transfer to the rear. I found this solved my car's tendency to snap oversteer when backing off throttle and stepping on brakes, the car wouldn't dive as much thus the rear had more grip.

please don't take this the wrong way, as it is just an observation regarding your recommendation to the OP, but to me, personally, designing the suspension configuration to compensate for a particular driving style is a less preferable way to set-up a car when compared to compensating/modifying a driving style to suit an optimised set-up...

[cordz]

please don't take this the wrong way, as it is just an observation regarding your recommendation to the OP, but to me, personally, designing the suspension configuration to compensate for a particular driving style is a less preferable way to set-up a car when compared to compensating/modifying a driving style to suit an optimised set-up...

in personal opinion, then.