Here are some posts and updates for every one to read. P.s VERY LONG BUT GOOD READING THOUGH.

Hypercoil Springs

--------------------------------------------------------------------------------

This is really a response to a privately-posted question, but the answer is worth sharing in public.

So then, what's the deal with Hypercoil springs?

Hypercoil does not make application-specific "lowering springs" like some other spring companies. They probably would wind you a custom spring that would fit in an OEM DSM application, but it'd probably set you back a couple of grand.

Instead, Real Racecars use a couple of common spring sizes, and Hypercoil makes springs that fit. The only exception is NASCAR, which uses a spring based on some late 60's GM OEM fitment - but because NASCAR is so big and so rich, that OEM fitment is now considered a "Real Racecar" fitment

Typically, a Real Racecar will use a spring that is either 2.5" in INNER diameter, or 2.25" inches in INNER diameter. An engineer has no real control over the OUTER diameter, because the OD is a function of the ID and the rate (stiffer springs use larger diameter wire)

They come in set lengths, from 3" to 12" by 1".

The big deal about Hypercoils is the extreme lengths they go to to ensure quality. A Hypercoil will never sag. A Hypercoil is guarenteed to be within 3% of it's indicated rate. Every single Hypercoil is rate-tested at the factory before it is shipped.

When you use a Hypercoil, you're using the exact same spring as an Indycar, CART car, WRC car etc etc etc. This is Real Racecar stuff. But because they have huge economies of scale, the springs are actually pretty inexpensive (in the ballpark of $60 per spring)

It's not very often that we get to use Real Racecar stuff and actually have it be CHEAP. Enjoy the opportunity!

To use Hypercoils on a DSM, you need to have a coilover kit - they will not fit without one. You also need coaxial upper spring hats (which has been discussed already)

What size depends on the ID of the spring hats, the length of the spring, and the rate you want. For Konis with native coilover hardware and appropriately-relocated snap ring grooves, that'll be 2.25" ID X 8" long by RATE. For most GC and EBAY-sourced stuff, 2.5" ID by 8" by RATE.

On my own car, I'm using 2.5" ID x 8" long X 900lbs/in on the front, and 2.5" x 8" long x 400lbs/in on the rear.

Something else that is helpful (heh) is the "helper spring" This is a flat-wound spring with minimal rate that is designed to collapse when the car's weight is applied to it, but expands when the wheel comes off the ground. It's useful to keep the spring from ratlling around on the perch in lowered applications. I use them on my car.
**

Quote:
EVERY spring manufacturer claims the same low variation in spring rate. Most of them are full of ****e.


Agreed - that's why we test the rates of springs here. We have an electronic spring rate checker that we use to see what the rate of any given spring really is.

The only spring that I've never seen fail is a Hypercoil. The "red" springs are hit and miss, and the no-name springs on some of the Japanese suspension kits are garbage.

Quote:
Your car has to push like a pig with those rates on there. Why are you running a 900# spring on the front?


Because that's what makes a 2G work.

2Gs are nose heavy, so the front suspension carries more of the car than the rear. The front spring/shock motion ratio is lower than the rear, so the wheel has more of a mechanical advantage over the spring in the front - the front springs are "softer" for a given rate. And the front roll centre is lower than the rear, which means the front roll moment arm is longer, which means the sprung mass has a larger mechanical advantage over the springs in roll.

All this adds up to make the front springs less effective, both in bump and in roll, than the rears, rate for rate. And the front springs need to carry more of the car. Generally, you want the front percentage of roll resistance to be equal to the front weight distribution - so that on a car that is 60% nose heavy, you want the front end to carry 60% of the roll resistance.

My weight distribution is 62/38, and my roll resistance distribution is 59/41, which should result in a car that is slightly LOOSE - and it is (at least on corner entry)

Quote:
Hey ** -FNR does this meanThe spring rates on a certain suspension system would then be all generic or would could they be selected


Practically speaking, generic. There's a pair of great big monster variables over which we have little control and can find little about - the tire, and the driver.

The tire has tremendous influence on the setup, both in its construction and in its dynamic attitude. For example, if the front tires are rolling over on their sidewalls due to insufficiant inflation pressure or insufficiant static/dynamic camber, then the front end is going to come loose and the springs can't do much about it (they CAN help with dynamic camber by adding more roll resistance and changing the angle of the sprung mass at max roll)

The driver also has enormous influence, because he can induce handling problems, and he reports on the over/under steer balance - and might get it wrong. It takes a lot of experience to be able to REALLY feel what the car is doing - and AWD cars don't make it any easier, because the diffs crosstalk and hide balance nuances that are easier to feel on cars that only drive one end of the car.

So it's tough to tell some random guy off the street that a given setup X is going to be perfect for him right out of the box. For example, I wouldn't recommend that just anybody put my setup on their car. There's so much spring in my car because I'm running 11" of great big sticky tires on each corner, primarily on concrete surfaces. The car sees transient cornering forces in excess of 1.6 G. It takes a lot of spring to keep the sprung mass under control when you've got that much lateral grip.

When we go to asphalt surfaces, it's not unusual to pull spring out of the car. The grip is less, so the cornering forces trying to roll the car are less, so we need less spring to keep the sprung mass under control.

For the general public who isn't racing against the Bob Tunnells, Vic Siases, Mark Daddios etc of the world, the concern is less "ultimate cornering power" and more about stance (ride height) and ride quality.

Ride quality is a direct function of the match between the springs and the shocks. My car, with all that spring, rides nice and smooth with no jarring or bouncing - because the shocks have been exceptionally well matched to the springs. OMG IT'S SO BOUNCY!!!! is almost always a shock/spring mismatch (sometimes because the car is sitting on the bumpstops, and bumpstops are really stiff springs)

So it's better for a street car to pick spring rates based on natural frequency, and ensure that the shocks match. If the natural frequency is higher than stock, the car will be both more responsive and be more tolerant to lowering (for bumps of a given amplitude, a lower ride height means more spring rate to keep the car from bottoming)

If a street guy can throw on our setup, and the ride quality is good and the car feels more responsive, we've done our job. If a race guy can throw on our setup, and he's got a good starting point for further development, we've done our job.

So the ATI setup that I'm developing (and yes I'm allowed to talk about it if specifiically asked, as I have been here - and if Management ever gets me a sponsorship quote I WILL be pitching my boss on actually sponsoring the forum) will be set up with a specific natural frequency and matching shocks.

Quote:
You my friend are retarded. His car absolutely MUST HANDLE LIKE ASS.


ROFL!

Let's see... on these spring rates the car won:

- 2002 SCCA ProSolo Street Modified National Championship
- 2002 SCCA ProSolo Honda Street Challenge Championship
- 2002 MachV "Ultimate DSM" trophy at the Buschur Racing DSM Shootout
- 2003 SCCA CENDIV Divsional Championship
- 2004 FIA AutoSlalom Canadian National Championship
- and a host of individual event wins at SCCA Pro and National Tour events in 2002, 2003, and 2004

Yup.... handles like ass.

For more info, check out http://farnorthracing.com

**


Quote:
If you are a fan of roll-resistance view, could you please say why. I understand the weight-transfer view (because I think that it's in Staniforth), but I don't quite get the roll-resistance view.


Strictly speaking, it really is "weight transfer" that we want to parallel the static weight distribution, and it is the weight transfer numbers that I use to determine what the expected final balance will be.

The roll resistance distribution and the weight transfer distribution are pretty close to each other - within a couple of percent - so I tend to use the terms interchangably.

The other issue is that there's a lot more involved in calculating weight transfer, so it takes a hell of a lot longer to explain. When you consider that the weight transfer via springs/bars is roughly double that of via roll centres, which is in turn roughly 5 times that of via the unsprung masses, it can be seen that roll resistance distribution is the dominant factor in determining weight transfer distribution.

So I simplify a little bit for the purposes of discussion.

Oh, it turns out I was reading the wrong cells for the quoted values given earlier - that was the RM rear sway bar numbers. The actual values are weight distribution 62/38, roll resistance 63/37, and weight transfer 59/41 - slighly loose. Raising the front springs to 1200lbs would exacly balance the car (at least on paper)

**

After the test fit, we decided we wanted to do one more protoype run before we released the parts. Ideally, these prototypes will be the final release configuration, and will need no further revisions.

Customers are not beta testers.

That means we're back in the machine shop queue.

Once the final prototypes have been cut and verified as OK to release, they'll go on sale.

Hopefully we'll be able to do a full release announcement once they're ready. I'm trying to negotiate forum sponsorship even as we speak.

**

Minor change to the front bolt circle spacing. Slightly larger change to the rear bolt circle spacing. Minor change to the OD of the plate. Change to thickness of spacers to pull top of shock rod away from hood.

Little stuff; nothing major at all. We just don't want to make a bunch of changes to the drawings, and then do a big production run and find that something got overlooked.

The machine shop credo is "if it matches the print, it's correct" so it behooves those of us making the drawings to make sure that what's on the print is what we want.

**

OK, I've just finished the fitment of the prototype kits.

It turns out that there is NO suspension travel improvement between a flat-hat and a coax hat. With the front suspension fully compressed to the point that the upper control arm contacted the upper fender well, there's still over an inch of shock travel left with the coax hat.

That's worth repeating - you lose NO suspension travel with a coax upper spring hat. In fact, I was able to nudge the shock rod down a little more to gain a little more hood clearence

I also took measurements as to exactly how much misalignment there is between the centreline of the shock rod and the upper mount surface plane. You get about 3-5 degrees in the the Y axis and 1-7 degrees in the X. At NO point is the shock rod EVER square to the upper mount plate. This picture

http://www.accuratetechnologies.com.../2/why_coax.jpg

Is actually pretty much representative of how bad things can get. The suspension can indeed get there during normal operation.

I took pictures to prove it; they'll be posted sometime.

I also now have the locations for the coilover snap ring grooves specced out. I just have to update the drawings with a few little changes to correct some minor fitment issues here and there, and then I can get on to speccing out spring rates.

It would be helpful if I had some corner weights from some 2G DSMs that weren't full-on Championship-winning autox cars. If you've got a stock or nearly so car, and you've got corner weights (taken with real race scales) could you please post them?

**

Learn: http://autocross.dsm.org/books.html

There's no need for donations. I'm putting together a stripped-down spreadsheet that'll be posted on autocross.dsm.org once I've finished organizing it.

I say "stripped down" because the version I've been using for the last few years has every single shock valving iteration in it, plus tons of other stuff that's there for my own amusement, but really isn't all that important in the greater picture. I live with the thing, I know how to navigate it.

Mind you, if anybody really WANTS to make a donation, I won't say no.