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11-19-2007, 10:49 AM | #1 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
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MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Spring Stiffness Comparison - Chart/Data
Updated
Data file and stiffness plots are attachments at the bottom of this post. Enjoy and look for updates as I test more springs. For those who haven't seen this before... Awhile ago I started using some of the wonderful test equipment I have here at work to test the different coilover springs I've been putting on my car. As a benefit to the community I decided to post the results here for everyone to see. Along the way I've had some discussions with Clint @ TiC, Colin @ Swift Springs, some engineer at Hyperco, Brian @ Vorshlag, and our wonderful moderator ButtDyno (John). Initial testing was done at my own discretion and to loads and calculation points that I decided were good enough. While talking with Swift they mentioned that the industry standard was to test the spring to its maximum "useable" stroke and calculate stiffness between 30% and 70% of that distance. While looking over Eibach's website I see that they use 20% to 70% of the "useable" stroke to find stiffness, contraditcing Swifts claim of an industry standard. To further remove any sense of an industry standard, Hyperco noted that they load each spring to a predetermine preload (which wasn't given to me) and then compress the spring 1 inch and take a data point. Then compress another inch and take a data point. They'll take as many data points as the spring allows and calculate the rate through those points. After some deliberation we determined that Hyperco's method makes the most sense. Not for volume of data or averaging points, but because they use a data point that is useful to most people. The springs are tested from 0 mm to 100 mm of displacement (machine limit, unless the "useable" stroke is less than 100 mm). Stiffness calculations are performed between the predetermined preload and 25 mm of compression. This was chosen to represent the displacement and stiffness through which most daily driving events occur. With the majority of race tracks being smoother than normal roads I expect that most of those inputs fall in this range of compression as well. For those who may be wondering, there is a difference between maximum stroke and the maximum "useable" stroke. "Useable" stroke is the amount of travel in the spring before the coils begin to contact and the spring rate starts to increase. For now the testing setup can only support linear, grounded, coilover springs. I have plans to develop a fixture capable of supporting OEM style springs, but need to find time and funds to get something built before I can begin testing. If you have some coilover springs that you'd like to have tested and rates verified, shoot me a PM and we can work something out. I'm personally interested in testing springs off some of the more popular coilovers that the community is purchasing these days (Megan, Buddy Club, Tein, KW, RCE, etc). Here are some pictures of the current setup. Pictured is one of ButtDyno's springs from Hyperco / Hypercoil.
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Last edited by Scooby921; 04-15-2008 at 08:56 AM. Reason: Updated data and chart...using my special "supporter" allowances to post an attachment :banana: |
11-19-2007, 02:46 PM | #2 |
Former Vendor
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Vehicle:Many Track Records Let us help you go fast! |
to which Scooby921 and I have been talking. If you have a set of blown stock struts with unmolested perches please contact us as we'd like to buy them to build the test rig.
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11-20-2007, 06:34 AM | #3 |
Scooby Newbie
Member#: 107389
Join Date: Feb 2006
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TXIC
Vehicle:2014 Honda Odyssey |
Scooby921, it looks like all the springs are fairly linear and true to their rate unless the differences are a bit too small to show up in the chart. (And if they are, then that's good, right?)
I can donate a rear 2005 STI strut housing. |
11-20-2007, 08:24 AM | #4 |
Scooby Newbie
Member#: 93606
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Location: Michigan
Vehicle:2002 WRX Wagon - WRB 2005 9-2X - SGM |
Nice to have objective data. I live in your same town and can offer the following springs for test:
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11-20-2007, 10:32 AM | #5 | |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Quote:
OK, so we have a strut housing / spring perch to use. I'm pretty sure I have front and rear topmounts from my '05 in the garage. I guess I just need a rear topmount from a bugeye to complete the fixtures. I'm really excited to see the difference in progressive rates and inflection points for the OEM style springs. I just hope the assembled fixtures are short enough to fit under the test machine. Last edited by Scooby921; 11-20-2007 at 10:49 AM. |
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11-29-2007, 03:04 AM | #6 |
Scooby Specialist
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NWIC
Location: Seattle, WA
Vehicle:2017 WRX (P) Lapis blue |
I have a set of bugeye rear top mount to loan you.
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11-30-2007, 12:03 AM | #7 | |
Scooby Guru
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Quote:
btw your fender braces are awesome, i recommend them to everyone now. |
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02-11-2008, 02:56 PM | #8 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Finally got around to testing the HKS springs. They are linear just like Eibach and Swift, but they are the furthest from their claimed spring rates.
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02-11-2008, 04:55 PM | #9 |
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
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MAIC
Location: NoVA
Vehicle:2018 Focus RS 2006 Evo #17 STU |
Hyperco OBD would be a good one to throw in there... their new springs are cheaper than the Swifts and have very similar specs. If I have enough time to ship them to you before I have to install them, I will.
john |
02-12-2008, 08:20 AM | #10 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
When do you plan on installing them? The test stand I've been using for testing will be tied up for the next month or two with durability testing of some engine mounts.
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02-12-2008, 08:22 AM | #11 |
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region:
MAIC
Location: NoVA
Vehicle:2018 Focus RS 2006 Evo #17 STU |
Well our first event is April 6th so they'll need to be on the car before then. I'll wait as long as I can
john |
02-12-2008, 08:53 AM | #12 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
I checked the test schedule again. That machine is only tied up through March 4th. If you send them around that time I can have 'em tested and back to you within a week.
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02-12-2008, 10:43 AM | #13 |
Scooby Guru
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Join Date: Jul 2001
Location: Plains of Eastern Montana
Vehicle:09 GH B+ |
nice work- funny I missed this thread the first time around
if you ever get it rigged for oe style springs that would certainly be useful for a bunch of folks |
02-13-2008, 01:27 AM | #14 |
Scooby Guru
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International
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Nice work! can't wait to see this chart grow. it will be nice to see some of the proprietary spring rate springs get debunked.
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02-13-2008, 01:49 AM | #15 |
Scooby Guru
Member#: 126441
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SCIC
Location: TPE
Vehicle:03 bugeye |
nice nice!! moaar springs pls.
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02-13-2008, 08:30 AM | #16 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Still gathering topmounts and a strut body / lower perch so I can build a test fixture and start testing OEM style springs.
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02-13-2008, 09:23 AM | #17 |
Scooby Guru
Member#: 126441
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Vehicle:03 bugeye |
^^you rock!
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02-13-2008, 01:00 PM | #18 | |
Scooby Guru
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Quote:
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02-13-2008, 01:10 PM | #19 |
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region:
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http://spreadsheets.google.com/pub?k...eL_KhwEw&gid=1
I can't see it (google docs blocked at work) but I bet there are plenty in there we don't have rates for. IIRC the Cobbs are one... |
02-13-2008, 01:19 PM | #20 |
Scooby Guru
Member#: 7958
Join Date: Jul 2001
Location: Plains of Eastern Montana
Vehicle:09 GH B+ |
it would also be interesting to see how close the rates actually are for those companies that post them
a buddy a long time ago tested the first Prodrive WRX springs- obviously they are not posting their rates |
02-13-2008, 03:12 PM | #21 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Well, I think I just found my strut body to hack up. Assuming it has topmounts attached...I'll have rears off of a bugeye outback sport. I'm assuming those are standard '02-'03 rears. If I can find my old topmounts in the garage I should have '04+ rears and fronts ready to go.
Anyone have a 6"x6"x1/2" steel plate they want to donate for the base of the test fixture? If you can machine it ahead of time, I'll need a hold bored in the center (whatever the diameter of a strut housing is about an inch below the perch). |
02-13-2008, 04:05 PM | #22 |
Scooby Guru
Member#: 140163
Join Date: Feb 2007
Chapter/Region:
MAIC
Location: 3MI Racing
Vehicle:03 STi hellaflunctional |
do you have any need for a usdm 04 sti spring set to test?
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02-14-2008, 08:16 AM | #23 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
Possibly. I'm going to start with whatever the locals have lying around. There are enough STi's here that we might not have to worry about shipping a set of those back and forth. Nonetheless, if people can start putting up a list of what they might have lying around the garage I can at least get started with a testing plan.
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02-14-2008, 01:33 PM | #24 |
Scooby Guru
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Join Date: Feb 2007
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well let me know. i have a set with about 35k miles on them sitting in my garage.
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03-06-2008, 09:09 AM | #25 |
Merci Buckets
Moderator Member#: 88606
Join Date: Jun 2005
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:2018 Grand Cherokee Velvet Red Pearl |
So I haven't gotten any further along with this because I'm still need to piece together my testing fixture for OEM springs. We've also been busy running durability tests that take several weeks and I haven't exactly been able to steal time on that particular test machine.
Anywhoo...my newest set of toys showed up in the mail yesterday. These will be tested individually and as pairs before they go on the car. |
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