07-23-2010, 12:28 PM
Join Date: Feb 2008
My Ride: e30
Originally Posted by TxZHP04
250 lb/in 14" springs tested at 7" stroke?
That gave me a pretty good chuckle. My springs aren't even 7" long and my rates are double that. Were those springs from a 4x4?
That covers the "technical" differences but doesn't really give a subjective assessment as to whether you can notice a difference between the various springs tested. You will absolutely feel a difference as compared to a progressive rate spring but how much difference does a 5% variation in rate across the stroke really make? And what about the not-easily-measurable reaction rates that supposedly give Swift springs a superior ride (according to the Swift fan in one of the other threads)?
I don't mean to be a lurker but I was just looking through and noticed this.
Those springs are for circle track used on the Swift website. That is the main market they are pitching this piece to. But this information is useful to you too because the longer the spring, it magnifies the consistencies of the stroke of the spring. Being tested at 7 inches of stroke on a 14 inch spring can give you a good idea of how their coilover spring would also react. Swifts biggest market is Nascar guys, and that is the spring rates and dimensions are the most popular set-up. Big bar soft spring setup in the front. In fact some cars run as low as 100lb 14 inch springs and runs through the corner fully coilbound or on the bumpstops. Swift works well for these guys because of the amount of stroke that is available in their spring.
I do not see the reason why you would chuckle at the test. For example:
You said your springs arent even 7 inches long. and double the spring rate. So lets say you have a 6inch 500lb spring in the front of your vehicle. The reason why we are putting it in the front is because the fronts of BMW's are macpherson which is pretty close to a 1/1 motion ratio. Now the curb weight for an E46 is 3300lbs. And the E46 is close to a 50/50 split. Lets just say the front is 1650 and so each corner weight of the front is 825 lbs. You are at 1.65" so already almost 2 inches into your compression of the spring in static form. In other words from driving you can, and will compress the spring 3 inches which is half the stoke of a 6inch spring, in other words you will feel the spike (just like the 7inch stroke on a 14 inch spring). Spring rate consistency is crucial for any form of racing, because that kind of spike will litterally get me lost in how I should setup a vehicle.
With real racing every little bit counts. I have tested countless number of times the science of the springs, and you also did not fully read my post that was reposted from another thread. Reaction rate is the mechanical lag time from the reaction of the shock to the spring. The Swift spring reacts instantaneously with the reaction of the shock. And the reason why it was not easily measureable was because we figured it out through a very expensive process. We had to put the vehicle on a shaker rig to finally figure it out. The reaction rate of a spring has to do with frequencies of the spring, and therefore the simplest test you can do is hit the spring with metal object like a spoon, and you can hear the differences in the spring. The Swift is a higher pitch ping then the other springs of the bunch. Now it has been said over and over that the Swift spring even with the same spring rate feel s much more compliant than the other linear coilover spring, and this is my theory in it being more compliant, as well as cooler tire temps around a circuit.
Most the testing I have done is compared to a Hiperco. The reason being it is better than the rest (Eibach, Volkland, H&R, Draco, Afco, and Integra). And yes the Shaker rig test was compared to a Hipercoil.
You apparently did not do the math for the 5% variation. 5% makes a good amount of difference in spring rate considering most domestic spring manufacturers go in 25-50 lb increments in their spring rates. If your running 800lb springs and their is a 5% difference then it ranges from about +/-40lbs. How can you label a spring that specific spring rate if it ranges all the way up or down from that spring rate. A spring rate should not be an average of numbers throughout its stroke. In this example it should be 800lbs every inch of compression. Hipercoil does a good job trying to be a accurate as possible with their spring, if you order a 150lb spring they will give you a spring with a label on top that says 153. Which is probably what they tested at. And sure enough when I tested it the first inch or so of stroke is 153 but then it hikes up from there.
And I am not a Swift fan. Like I said previously if I find a better spring out there I would use that. For the vehicles I setup I am constantly looking for something better. I revalve and setup shocks not only for Circle Track, but touring cars, drag cars, and formula cars.
I used to only use Hipercoil spring. I only started looking deep into other brands of springs because many of the circle track racers that I setup for would have to keep coming back race after race because the Hipercoils will lose rate and height, and when this happens the corner weights get really thrown off, and sometimes will even get disqualified because after the race the techs will check rideheight again, and if its below what's written on the rules, your done. So I started looking for something more durable and I stumbled upon Swift. They told me that their springs are much more durable and so I had one of my customers use it. And it was true it did not sag. From what I have seen through various events the springs last generally 4 times longer than Hipercoils. But some can get through a whole season without it ever sagging. As I started using Swift springs for most my suspension setups, the dirt oval racers and the touring car racers are the ones that say they feel an enormous difference in the spring, and that is what got me into researching the crap out of them. Now understand that circle track racing is extremely hard on the spring, Sagging is a very normal occurrence with this form of racing. We get the light weight 14 inch spring and preload it about 2-3 inches from coilbind, and then these guys drive the crap out of them. Sagging is definitely not an issue that you have to be worried about.
I couldn't even say Swift is the best manufacturer out there. There is a company that makes coilover springs called Renton, These springs are about 1500dollars a piece, and are still a magnetic steel. I do not own one nor will I ever pay that much for these springs. I have tested them though, and the characteristics of these were weird. The spring rates were digressive. So it got softer as you compressed the spring. Which is illegal by Nascar rules but somehow these springs are allowed and that is what everyone uses in Sprint Cup.
I will end this by saying that suspension tuning in general is all just a theory, It is a black art. Some people like the way I set up their suspension and will swear by every decision I make, others will not. And that is the way it has always been. One can have the exact same car as the other, but setup the suspensions completely different and clock the same times around the track. So if you like the setup then stick with it, if you have the money test it out, but there is no use in badmouthing a product if you have no experience with it.