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View Full Version : FWD Suspension Setup (Questions)


Grant Galloway
09-02-2015, 06:04 PM
Curious to know what guys are running for suspension? I have a set of ISC coilovers I purchased last year, They have very limited adjustability Rebound and Compression are done together!

The springs are 8KG front and 5.5KG rear

The car feels like it really rolls the front quite a bit, factory front sway bar and a progress 24mm adjustable rear.

I want to buy a new set of coilovers, but not sure how far I want to go! Will I see a huge improvement investing $3000 + dollars

Scott does my setups and we have slowly got to the point of making it more aggressive.

I ran in GT3 last weekend, and felt I was fairly competitive.

The 6 PIP's I take for these, probably makes me over a second quicker over the factory stilts the car sat on; however my car is probably not optimized.

I guess I could spend as much as I needed, but where do you draw the line on a car worth $14,000

Any insight would be appreciated!

Grant

Greg Campbell
09-02-2015, 06:41 PM
I want to buy a new set of coilovers, but not sure how far I want to go! Will I see a huge improvement investing $3000 + dollars

Grant

Yes, a top shelf coilover suspension is the second best bang for your buck (after tires). I am not aware of the company you reference, nor do I know much about what spring rate is required for your civic.

If you are going to take the suspension PIPs make them the best you can.

Slowpoke
09-02-2015, 06:52 PM
We have the HADA knowledge around here to help. At first blush, rear spring rate is ridiculously low. Aren't you McPherson strut front, multilink rear?

wparsons
09-03-2015, 12:19 PM
Shocks are probably more important than tires, really good shocks will give you a lot more mechanical traction.

The ones I've been looking at range from decent ones around $2300 usd (RCE TII, they're KW 2 way clubsports valved and sprung to RCE specs) up to about $6500 usd (JRZ RS Pro 2 way).

Grant Galloway
09-03-2015, 01:29 PM
I believe the biggest problem is that it is too lightly sprung, especially the rears!

My car does not like to break traction at all, the soft springs likely allow to much weight transfer. It's very easy to drive though!

I do run a square setup 225/45/17 with RE71R's ( I could go wider front ) But I like rotating tires.

The car has tremendous potential, makes a ton of power for a N/A 2.0L

I have no doubt if I can get the handling to where it needs to be, it would run up front.

Snizzoop
09-03-2015, 01:54 PM
For reference, I run 600lb/in (10.7kg/mm) front springs and 800lb/in (14.3kg/mm) rear springs on my roughly 2250lb 1995 Civic coupe. I also run a 24mm ASR rear sway bar...no sway bar in the front. I use the car strictly for autoslalom...so having a car that will actually turn is key.

The car does roll a bit in the front...so I've been considering swapping the rates front to rear, and going with an even bigger rear bar...or just upping the front spring rate...or going up all around.

The suspension design and weights of our cars aren't the same...so I'm unsure of how helpful this info really is. The nice thing for me is that there is SO much info/parts for EG Civics, I can easily read and try out different setups.

thgear
09-03-2015, 02:00 PM
My car does not like to break traction at all, the soft springs likely allow to much weight transfer. It's very easy to drive though!


soft springs reduce the rate ofweight transfer

stiff springs increase the rate of weight transfer

the amount of weight transfer during any given side load is derived from the relationship of weight, center of gravity, and track width...nothing else

spring stiffness controls the rate at which that weight is transferred (often referred to as "response" or "how quickly the car sets in a corner") and is responsible for the relative position of your chassis and the wheel via your suspension geometry.

If you understand why any vehicle rolls at all, you will understand that it's not inherently bad... the only real negatives to excessive roll are a) the tire losing optimal position relative to the road via bad suspension geometry and b) losing aerodynamic stability by allowing more air to enter under the car.

if you're a fancy-pants engineer and are not restricted by production limits... you can design a car that can roll all it wants but the wheels will stay perpendicular to the ground

the MacPherson strut design, found in many vehicles, is unfortunately, not such a design. And so a certain amount of spring and swaybar stiffness is required to keep the tire more less at optimal angles to the road. This is a compromise, as lower spring rates translate into greater mechanical grip.


so back to your problem, which I feel is having too great a disparity between front and rear spring rate.

Having much stiffer springs in the front is making your front tires reach their maximum grip before the rears do. The front of the car "settles" before the rear, and so your ultimate cornering potential is dictated almost entirely by your front outside side. The rear wheels, which do much less on a FWD car in the first place, are never fully engaged, they never get a chance to fully load up, and so serve no other purpose than to prevent the rear of your car from dragging on the ground.

If you raise your rear rates, then the weight transfer of the rear might happen in tandem with the front, giving you slightly more neutral control if you're a smooth driver (tendency to oversteer if you're not)

Then you have to understand wheel rates and contact patches. The rear is lighter than the front, so you may not need as wider tires in the rear than the front, because at the end of the day what you're really trying to balance is the tire contact patch during cornering... get that balanced and the car will feel neutral.

will a $3000 suspension help you? Only if you know what you're doing.

I suggest you read up on the physics involved before you make that jump, or you'll forever be chasing knobs, dials, and perches trying to find that elusive edge.

Grant Galloway
09-05-2015, 04:07 PM
Thanks for the feedback, looking at some different options.

Grant

iamthewheelman
09-05-2015, 05:58 PM
I can say with certainty that your rear spring rates are far to low. The fronts are probably not far off for a good starting point, I'd up them slightly to around 500lbs or 9k. I would say that you should be starting at about 700lbs or 12.5k for the rear, but I wouldn't be surprised if after some testing you would want to up the rear rates slightly, or maybe a stiffer rear bar.

Look into Redshift Motorsports, they build a set of coilovers for 8th gen Civic's using Koni shocks with Ground Control perches and Eibach springs. They use all the same components I use in my car currently and I have been happy with my setup, they are probably better than the off shore brands for the same money, but not by any substantial margin.

I have never owned a set of high dollar shocks but from the extensive dreaming/research I have done, MCS and JRZ seems to be the two best options if they are available to you.

Lloyd_
09-05-2015, 06:48 PM
I think Dennis Grant's recommendation for target natural frequencies and FWD setup is pretty solid. http://farnorthracing.com/autocross_secrets.html

Make sure you're getting as much load transfer as possible in the rear (I would look for a no load or totally lifted inside rear, although obviously there is much debate as to if it should actually be off the ground or not).

My takeaway from your TMP video was that the car could be set up looser and with more damping. But that's just a video :)

Being able to rotate tires is really great. But FWD is so abusive to front tires it might be worth just sucking it up and putting a bigger front tire on it.