iNfEk

iTrader: (33)

I'm just curious when looking at the 'spring rate' on coilovers how you determine if they will be hard or soft springs that come with them?

A lot of coilover systems that I've been looking at say numbers like Front: 8 Rear: 6. I believe they are measured in kgf/mm. What does that mean to me and the other people looking to improve handling on their car for AUTO-X and perhaps daily driving?

What is the formula and why would I need to convert them to lbs/in?

Also, preload / unload what does that mean for the spring for coilovers?

Helper springs... do they affect the spring rates?

Inverted strut or Non-Inverted struts? Pros / Cons?

Jon

iNfEk

iTrader: (33)

bump

caterpill

iTrader: (11)

The thread looks blank; i'll try to stick some words in hereee.....

Will try to help. (Disclaimer: I don't really know what i'm taking about.)

Kg/mm is just another form of spring rate measurement, as you know. It doesn't really matter how they're measured, as long as you know how hard they are. 8 kg/mm is about 448lbs/in, and 6 is about 336 lbs/in. The formula (did a quick search)
= "To convert from kg/mm to lbs/in divide by 0.0179, and multiply to go from lbs/in to kg/mm"

To me, if you look at the stock 2002 WRX Sedan (MT) spring rates, 163lbs/in (F) 119lbs/in(R), you'll know that a 8kg/6kg suspension setup would feel that much stiffer then stock. Also, you'd kinda associate the "feel" of the car with the ratio of front to rear spring rate. For instance; a stock WRX may "understeer" with the stock springrates, 163/119. If you increase both springrates equally, technically all you're doing is adjusting roll stiffness, and in turn, camber change and general response from the car when you turn. So less camber change due to increased roll stiffness may equate to *slightly* more grip in the turn. But when you start playing with the balance (stiffness) from front to rear, you change more then just roll stiffness, but how the car "handles". Of course, raising only the front rate tends to give more understeer, while raising the rear rate gives you more oversteer/twitchyness, etc.

Manufacturers choose a spring and damping rate that best suits their goals when R&D testing, let it be for ride comfort, performance, or a compromise of both. People who auto-x probably have a base coilover setup to begin with, and start changing springs out within their coilover's valving ability to adjust feel of the car dependant on the track. Honestly, for heavy track racers it matters, but for most people who just want to have fun, having adjustable front and rear swaybars are cheaper and allow similar adjustment to handling.

Converting kg/mm to lbs/in is just to give an idea of how stiff the springs are. Simple metric system to our decimal system conversion.

It is unclear to me how Preload/No preload affects suspension performance. Preload would just basically be pre-compressing the spring; so when the shock is fully extended, the spring is still compressed and is under pressure. When there is no preload, the spring is not putting any pressure on the stock when it's fully extended.

Helper springs do affect the spring rate, but there are two types. A helper is usually a small, soft spring that helps keep the spring seated on a coilover with 1-way height adjustment, that is when you move the lower spring perch when lowering/raising the car. So when your car 3-wheels on a driveway or on the track, the spring does not move off the perches and cause damage/an accident. So a helper just takes up the slack. When the car is on the ground, the helper spring is fully compressed to coil bind and is effectively a solid steel spacer.

There are "Tender" springs, which look similar to helper springs, but are much stiffer and actually change the springrate. They are used to create progressive springrates. Tender springs are not fully compressed when the car is on the ground.

The benefits of inverted struts, from what i've heard;

Inverted struts are more rigid for more cornering stability, less flex.
Inverted struts are able to dissipate more heat. (Durability?)
Inverted struts contribute to less unsprung weight (shock cylinder is connected to the chassis, instead of the knuckle)
Inverted struts have a larger piston capacity. (More responsive valving)

Dunno what the cons are. Some say inverted struts need to be rebuilt in shorter intervals, but I don't have any idea why that's suggested.

I hope this helped some.
Feel free to correct me on any statements made above, as they are purely heresy. hohoho.

caterpill

iTrader: (11)

Oh, I forgot to add. Some suspension companies tune with slightly overdamped shocks, which allows the car to feel a little more comfortable while still being fairly stiff. An example of this is the stock STi's struts; it is overdamped.

Without getting into much detail, a suspension with 8kg/6kg springrates can be made to "feel" (in responsiveness) similar to a suspension with 10kg/6kg springrates simply by adjusting damping. A compromise in ride quality is achieved as the 8kg/6kg springrates should "take" bumps better.

It gets really complex, and boggles the mind. That is the fun in playing with suspension.

iNfEk

iTrader: (33)

Yeah... I get the just of it. I did however read up on it but as soon as I start getting in to the "meat" of the topic it gets all blurry to me and I feel sick... LOL

So is it my understanding that the LOWER the number in the spring rate = the stiffer the ride?

I did find some good information from HKS regarding mono-tube design vs twin-tube design suspension. http://www.hksusa.com/info/?id=2838

mono-tube design is primarily used for inverted struts whereas twin-tube design is used for non-inverted.

Anyone else can clear the cobbwebs a little more or ways to put it into a smaller pin to swallow would be great!

Thanks again,

Jon

caterpill

iTrader: (11)

Just like the lbs/in, a higher number is stiffer.

So like if you sit on a spring that is like 50 lbs/in, it will smash like butter, but if you sit on a spring that is 500lbs/in, it won't even smash at all.

iNfEk

iTrader: (33)

oh ok. so it's the opposite then. Thanks

WRXed

iTrader: (7)

jon - give me a call later and we can go over this in detail. i hate typing too much.

Hoppie

iTrader: (4)

I'm stunned to see Jon asking a question. For he is one of the gurus. Goes to show even the scholars don't know everything. Except Ty but he is a freak of nature.

iNfEk

iTrader: (33)

LOL...

Hope all is well!

I'm asking since I don't know the answer. This is how i-club grows as a group when people contribute or as questions that would help the rest of the group grow

Jon

sneezerboi

iTrader: (9)

Those are some good rates for a daily driver/semi track car (the 8/6 f/r). Take note, wagon drivers, it's sometimes recommended we use *slightly* stiffer rates in the rear (8/7).

As you go w/higher rates, stiffness is way up and transitions are quick, but then it becomes imperative that you get some good, sticky tires to compensate. I've seen people who go with 9/7 or even 10/8 f/r rates and those are pretty unbearable for daily driving.

WRXed

iTrader: (7)

i think the balance between the the compression and rebound rates are more important that just the spring rates. also picking the right suspension setup needs to match the driving style of each person.

91sleeper

iTrader: (13)

i just wish i could go 12/10. i love a good stiffie.

iNfEk

iTrader: (33)

well meganracings track edition coilovers are 12F/10R

I'm also looking into STANCE coilovers http://www.stancesus.com/

They look great!

Jon

91sleeper

iTrader: (13)

^^they don't make for my car but i can be happy with the whitelines.